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High Availability Add-On Reference

Red Hat Enterprise Linux 7

Reference Document for the High Availability Add-On for Red Hat Enterprise Linux 7

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Steven Levine

Red Hat Customer Content Services

Abstract

Red Hat High Availability Add-On Reference provides reference information about installing, configuring, and managing the Red Hat High Availability Add-On for Red Hat Enterprise Linux 7.

Chapter 1. Red Hat High Availability Add-On Configuration and Management Reference Overview

This document provides descriptions of the options and features that the Red Hat High Availability Add-On using Pacemaker supports. For a step by step basic configuration example, see Red Hat High Availability Add-On Administration.
You can configure a Red Hat High Availability Add-On cluster with the pcs configuration interface or with the pcsd GUI interface.

1.1. New and Changed Features

This section lists features of the Red Hat High Availability Add-On that are new since the initial release of Red Hat Enterprise Linux 7.

1.1.1. New and Changed Features for Red Hat Enterprise Linux 7.1

Red Hat Enterprise Linux 7.1 includes the following documentation and feature updates and changes.

1.1.2. New and Changed Features for Red Hat Enterprise Linux 7.2

Red Hat Enterprise Linux 7.2 includes the following documentation and feature updates and changes.

1.1.3. New and Changed Features for Red Hat Enterprise Linux 7.3

Red Hat Enterprise Linux 7.3 includes the following documentation and feature updates and changes.
Additionally, small clarifications and corrections have been made throughout this document.

1.1.4. New and Changed Features for Red Hat Enterprise Linux 7.4

Red Hat Enterprise Linux 7.4 includes the following documentation and feature updates and changes.

1.1.5. New and Changed Features for Red Hat Enterprise Linux 7.5

Red Hat Enterprise Linux 7.5 includes the following documentation and feature updates and changes.

1.2. Installing Pacemaker configuration tools

You can use the following yum install command to install the Red Hat High Availability Add-On software packages along with all available fence agents from the High Availability channel.
# yum install pcs pacemaker fence-agents-all
Alternately, you can install the Red Hat High Availability Add-On software packages along with only the fence agent that you require with the following command.
# yum install pcs pacemaker fence-agents-model
The following command displays a listing of the available fence agents.
# rpm -q -a | grep fence
fence-agents-rhevm-4.0.2-3.el7.x86_64
fence-agents-ilo-mp-4.0.2-3.el7.x86_64
fence-agents-ipmilan-4.0.2-3.el7.x86_64
...
The lvm2-cluster and gfs2-utils packages are part of ResilientStorage channel. You can install them, as needed, with the following command.
# yum install lvm2-cluster gfs2-utils

Warning

After you install the Red Hat High Availability Add-On packages, you should ensure that your software update preferences are set so that nothing is installed automatically. Installation on a running cluster can cause unexpected behaviors.

1.3. Configuring the iptables Firewall to Allow Cluster Components

Note

The ideal firewall configuration for cluster components depends on the local environment, where you may need to take into account such considerations as whether the nodes have multiple network interfaces or whether off-host firewalling is present. The example here, which opens the ports that are generally required by a Pacemaker cluster, should be modified to suit local conditions.
Table 1.1, “Ports to Enable for High Availability Add-On” shows the ports to enable for the Red Hat High Availability Add-On and provides an explanation for what the port is used for. You can enable all of these ports by means of the firewalld daemon by executing the following commands.
# firewall-cmd --permanent --add-service=high-availability
# firewall-cmd --add-service=high-availability

Table 1.1. Ports to Enable for High Availability Add-On

PortWhen Required
TCP 2224
Required on all nodes (needed by the pcsd Web UI and required for node-to-node communication)
It is crucial to open port 2224 in such a way that pcs from any node can talk to all nodes in the cluster, including itself. When using the Booth cluster ticket manager or a quorum device you must open port 2224 on all related hosts, such as Booth arbiters or the quorum device host.
TCP 3121
Required on all nodes if the cluster has any Pacemaker Remote nodes
Pacemaker's crmd daemon on the full cluster nodes will contact the pacemaker_remoted daemon on Pacemaker Remote nodes at port 3121. If a separate interface is used for cluster communication, the port only needs to be open on that interface. At a minimum, the port should open on Pacemaker Remote nodes to full cluster nodes. Because users may convert a host between a full node and a remote node, or run a remote node inside a container using the host's network, it can be useful to open the port to all nodes. It is not necessary to open the port to any hosts other than nodes.
TCP 5403
Required on the quorum device host when using a quorum device with corosync-qnetd. The default value can be changed with the -p option of the corosync-qnetd command.
UDP 5404
Required on corosync nodes if corosync is configured for multicast UDP
UDP 5405
Required on all corosync nodes (needed by corosync)
TCP 21064
Required on all nodes if the cluster contains any resources requiring DLM (such as clvm or GFS2)

1.4. The Cluster and Pacemaker Configuration Files

The configuration files for the Red Hat High Availability add-on are corosync.conf and cib.xml.
The corosync.conf file provides the cluster parameters used by corosync, the cluster manager that Pacemaker is built on. In general, you should not edit the corosync.conf directly but, instead, use the pcs or pcsd interface. However, there may be a situation where you do need to edit this file directly. For information on editing the corosync.conf file, see Editing the corosync.conf file in Red Hat Enterprise Linux 7.
The cib.xml file is an XML file that represents both the cluster’s configuration and current state of all resources in the cluster. This file is used by Pacemaker's Cluster Information Base (CIB). The contents of the CIB are automatically kept in sync across the entire cluster Do not edit the cib.xml file directly; use the pcs or pcsd interface instead.

1.5. Cluster Configuration Considerations

When configuring a Red Hat High Availability Add-On cluster, you must take the following considerations into account:
  • Red Hat does not support cluster deployments greater than 16 full cluster nodes. It is possible, however, to scale beyond that limit with remote nodes running the pacemaker_remote service. For information on the pacemaker_remote service, see Section 9.4, “The pacemaker_remote Service”.
  • The use of Dynamic Host Configuration Protocol (DHCP) for obtaining an IP address on a network interface that is utilized by the corosync daemons is not supported. The DHCP client can periodically remove and re-add an IP address to its assigned interface during address renewal. This will result in corosync detecting a connection failure, which will result in fencing activity from any other nodes in the cluster using corosync for heartbeat connectivity.

1.6. Updating a Red Hat Enterprise Linux High Availability Cluster

Updating packages that make up the RHEL High Availability and Resilient Storage Add-Ons, either individually or as a whole, can be done in one of two general ways:
  • Rolling Updates: Remove one node at a time from service, update its software, then integrate it back into the cluster. This allows the cluster to continue providing service and managing resources while each node is updated.
  • Entire Cluster Update: Stop the entire cluster, apply updates to all nodes, then start the cluster back up.

Warning

It is critical that when performing software update procedures for Red Hat Enterprise LInux High Availability and Resilient Storage clusters, you ensure that any node that will undergo updates is not an active member of the cluster before those updates are initiated.
For a full description of each of these methods and the procedures to follow for the updates, see Recommended Practices for Applying Software Updates to a RHEL High Availability or Resilient Storage Cluster.

1.7. Issues with Live Migration of VMs in a RHEL cluster

Information on support policies for RHEL high availability clusters with virtualized cluster members can be found in Support Policies for RHEL High Availability Clusters - General Conditions with Virtualized Cluster Members. As noted, Red Hat does not support live migration of active cluster nodes across hypervisors or hosts. If you need to perform a live migration, you will first need to stop the cluster services on the VM to remove the node from the cluster, and then start the cluster back up after performing the migration.
The following steps outline the procedure for removing a VM from a cluster, migrating the VM, and restoring the VM to the cluster.

Note

Before performing this procedure, consider the effect on cluster quorum of removing a cluster node. For example, if you have a three node cluster and you remove one node, your cluster can withstand only one more node failure. If one node of a three node cluster is already down, removing a second node will lose quorum.
  1. If any preparations need to be made before stopping or moving the resources or software running on the VM to migrate, perform those steps.
  2. Move any managed resources off the VM. If there are specific requirements or preferences for where resources should be relocated, then consider creating new location constraints to place the resources on the correct node.
  3. Place the VM in standby mode to ensure it is not considered in service, and to cause any remaining resources to be relocated elsewhere or stopped.
    # pcs cluster standby VM
  4. Run the following command on the VM to stop the cluster software on the VM.
    # pcs cluster stop
  5. Perform the live migration of the VM.
  6. Start cluster services on the VM. If cluster services had been enabled before migration, you can enable them again.
    # pcs cluster start
    # pcs cluster enable
  7. Take the VM out of standby mode.
    # pcs cluster unstandby VM
  8. If you created any temporary location constraints before putting the VM in standby mode, adjust or remove those constraints to allow resources to go back to their normally preferred locations.

Chapter 2. The pcsd Web UI

This chapter provides an overview of configuring a Red Hat High Availability cluster with the pcsd Web UI.

2.1. pcsd Web UI Setup

To set up your system to use the pcsd Web UI to configure a cluster, use the following procedure.
  1. Install the Pacemaker configuration tools, as described in Section 1.2, “Installing Pacemaker configuration tools”.
  2. On each node that will be part of the cluster, use the passwd command to set the password for user hacluster, using the same password on each node.
  3. Start and enable the pcsd daemon on each node:
    # systemctl start pcsd.service
    # systemctl enable pcsd.service
  4. On one node of the cluster, authenticate the nodes that will constitute the cluster with the following command. After executing this command, you will be prompted for a Username and a Password. Specify hacluster as the Username.
    # pcs cluster auth node1 node2 ... nodeN
  5. On any system, open a browser to the following URL, specifying one of the nodes you have authorized (note that this uses the https protocol). This brings up the pcsd Web UI login screen.
    https://nodename:2224
    
  6. Log in as user hacluster. This brings up the Manage Clusters page as shown in Figure 2.1, “Manage Clusters page”.
    Manage Clusters page

    Figure 2.1. Manage Clusters page

2.2. Creating a Cluster with the pcsd Web UI

From the Manage Clusters page, you can create a new cluster, add an existing cluster to the Web UI, or remove a cluster from the Web UI.
  • To create a cluster, click on Create New and enter the name of the cluster to create and the nodes that constitute the cluster. You can also configure advanced cluster options from this screen, including the transport mechanism for cluster communication, as described in Section 2.2.1, “Advanced Cluster Configuration Options”. After entering the cluster information, click Create Cluster.
  • To add an existing cluster to the Web UI, click on Add Existing and enter the host name or IP address of a node in the cluster that you would like to manage with the Web UI.
Once you have created or added a cluster, the cluster name is displayed on the Manage Cluster page. Selecting the cluster displays information about the cluster.

Note

When using the pcsd Web UI to configure a cluster, you can move your mouse over the text describing many of the options to see longer descriptions of those options as a tooltip display.

2.2.1. Advanced Cluster Configuration Options

When creating a cluster, you can click on Advanced Options to configure additional cluster options, as shown in Figure 2.2, “Create Clusters page”. For information about the options displayed, move your mouse over the text for that option.
Note that you can configure a cluster with Redundant Ring Protocol by specifying the interfaces for each node. The Redundant Ring Protocol settings display will change if you select UDP rather than the default value of UDPU as the transport mechanism for the cluster.
Create Clusters page

Figure 2.2. Create Clusters page

2.2.2. Setting Cluster Management Permissions

There are two sets of cluster permissions that you can grant to users:
  • Permissions for managing the cluster with the Web UI, which also grants permissions to run pcs commands that connect to nodes over a network. This section describes how to configure those permissions with the Web UI.
  • Permissions for local users to allow read-only or read-write access to the cluster configuration, using ACLs. Configuring ACLs with the Web UI is described in Section 2.3.4, “Configuring ACLs”.
For further information on user permissions, see Section 4.5, “Setting User Permissions”.
You can grant permission for specific users other than user hacluster to manage the cluster through the Web UI and to run pcs commands that connect to nodes over a network by adding them to the group haclient. You can then configure the permissions set for an individual member of the group haclient by clicking the Permissions tab on the Manage Clusters page and setting the permissions on the resulting screen. From this screen, you can also set permissions for groups.
You can grant the following permissions:
  • Read permissions, to view the cluster settings
  • Write permissions, to modify cluster settings (except for permissions and ACLs)
  • Grant permissions, to modify cluster permissions and ACLs
  • Full permissions, for unrestricted access to a cluster, including adding and removing nodes, with access to keys and certificates

2.3. Configuring Cluster Components

To configure the components and attributes of a cluster, click on the name of the cluster displayed on the Manage Clusters screen. This brings up the Nodes page, as described in Section 2.3.1, “Cluster Nodes”. This page displays a menu along the top of the page, as shown in Figure 2.3, “Cluster Components Menu”, with the following entries:
Cluster Components Menu

Figure 2.3. Cluster Components Menu

2.3.1. Cluster Nodes

Selecting the Nodes option from the menu along the top of the cluster management page displays the currently configured nodes and the status of the currently selected node, including which resources are running on the node and the resource location preferences. This is the default page that displays when you select a cluster from the Manage Clusters screen.
You can add or remove nodes from this page, and you can start, stop, restart, or put a node in standby mode. For information on standby mode, see Section 4.4.5, “Standby Mode”.
You can also configure fence devices directly from this page, as described in Section 2.3.3, “Fence Devices”. by selecting Configure Fencing.

2.3.2. Cluster Resources

Selecting the Resources option from the menu along the top of the cluster management page displays the currently configured resources for the cluster, organized according to resource groups. Selecting a group or a resource displays the attributes of that group or resource.
From this screen, you can add or remove resources, you can edit the configuration of existing resources, and you can create a resource group.
To add a new resource to the cluster, click Add. The brings up the Add Resource screen. When you select a resource type from the dropdown Type menu, the arguments you must specify for that resource appear in the menu. You can click Optional Arguments to display additional arguments you can specify for the resource you are defining. After entering the parameters for the resource you are creating, click Create Resource.
When configuring the arguments for a resource, a brief description of the argument appears in the menu. If you move the cursor to the field, a longer help description of that argument is displayed.
You can define as resource as a cloned resource, or as a master/slave resource. For information on these resource types, see Chapter 9, Advanced Configuration.
Once you have created at least one resource, you can create a resource group. For information on resource groups, see Section 6.5, “Resource Groups”.
To create a resource group, select a resource that will be part of the group from the Resources screen, then click Create Group. This displays the Create Group screen. Enter a group name and click Create Group. This returns you to the Resources screen, which now displays the group name for the resource. After you have created a resource group, you can indicate that group name as a resource parameter when you create or modify additional resources.

2.3.3. Fence Devices

Selecting the Fence Devices option from the menu along the top of the cluster management page displays Fence Devices screen, showing the currently configured fence devices.
To add a new fence device to the cluster, click Add. The brings up the Add Fence Device screen. When you select a fence device type from the drop-down Type menu, the arguments you must specify for that fence device appear in the menu. You can click on Optional Arguments to display additional arguments you can specify for the fence device you are defining. After entering the parameters for the new fence device, click Create Fence Instance.
For information on configuring fence devices with Pacemaker, see Chapter 5, Fencing: Configuring STONITH.

2.3.4. Configuring ACLs

Selecting the ACLS option from the menu along the top of the cluster management page displays a screen from which you can set permissions for local users, allowing read-only or read-write access to the cluster configuration by using access control lists (ACLs).
To assign ACL permissions, you create a role and define the access permissions for that role. Each role can have an unlimited number of permissions (read/write/deny) applied to either an XPath query or the ID of a specific element. After defining the role, you can assign it to an existing user or group.

2.3.5. Cluster Properties

Selecting the Cluster Properties option from the menu along the top of the cluster management page displays the cluster properties and allows you to modify these properties from their default values. For information on the Pacemaker cluster properties, see Chapter 12, Pacemaker Cluster Properties.

Chapter 3. The pcs Command Line Interface

The pcs command line interface controls and configures corosync and Pacemaker by providing an interface to the corosync.conf and cib.xml files.
The general format of the pcs command is as follows.
pcs [-f file] [-h] [commands]...

3.1. The pcs Commands

The pcs commands are as follows.

3.2. pcs Usage Help Display

You can use the -h option of pcs to display the parameters of a pcs command and a description of those parameters. For example, the following command displays the parameters of the pcs resource command. Only a portion of the output is shown.
# pcs resource -h
Usage: pcs resource [commands]...
Manage pacemaker resources
Commands:
    show [resource id] [--all]
        Show all currently configured resources or if a resource is specified
        show the options for the configured resource.  If --all is specified
        resource options will be displayed

    start <resource id>
        Start resource specified by resource_id
...

3.3. Viewing the Raw Cluster Configuration

Although you should not edit the cluster configuration file directly, you can view the raw cluster configuration with the pcs cluster cib command.
You can save the raw cluster configuration to a specified file with the pcs cluster cib filename command as described in Section 3.4, “Saving a Configuration Change to a File”.

3.4. Saving a Configuration Change to a File

When using the pcs command, you can use the -f option to save a configuration change to a file without affecting the active CIB.
If you have previously configured a cluster and there is already an active CIB, you use the following command to save the raw xml file.
pcs cluster cib filename
For example, the following command saves the raw xml from the CIB into a file name testfile.
pcs cluster cib testfile
The following command creates a resource in the file testfile1 but does not add that resource to the currently running cluster configuration.
# pcs -f testfile1 resource create VirtualIP ocf:heartbeat:IPaddr2 ip=192.168.0.120 cidr_netmask=24 op monitor interval=30s
You can push the current content of testfile to the CIB with the following command.
pcs cluster cib-push filename

3.5. Displaying Status

You can display the status of the cluster and the cluster resources with the following command.
pcs status commands
If you do not specify a commands parameter, this command displays all information about the cluster and the resources. You display the status of only particular cluster components by specifying resources, groups, cluster, nodes, or pcsd.

3.6. Displaying the Full Cluster Configuration

Use the following command to display the full current cluster configuration.
pcs config

3.7. Displaying The Current pcs Version

The following command displays the current version of pcs that is running.
pcs --version

3.8. Backing Up and Restoring a Cluster Configuration

As of the Red Hat Enterprise Linux 7.1 release, you can back up the cluster configuration in a tarball with the following command. If you do not specify a file name, the standard output will be used.
pcs config backup filename
Use the following command to restore the cluster configuration files on all nodes from the backup. If you do not specify a file name, the standard input will be used. Specifying the --local option restores only the files on the current node.
pcs config restore [--local] [filename]

Chapter 4. Cluster Creation and Administration

This chapter describes how to perform basic cluster administration with Pacemaker, including creating the cluster, managing the cluster components, and displaying cluster status.

4.1. Cluster Creation

To create a running cluster, perform the following steps:
  1. Start the pcsd on each node in the cluster.
  2. Authenticate the nodes that will constitute the cluster.
  3. Configure and sync the cluster nodes.
  4. Start cluster services on the cluster nodes.
The following sections described the commands that you use to perform these steps.

4.1.1. Starting the pcsd daemon

The following commands start the pcsd service and enable pcsd at system start. These commands should be run on each node in the cluster.
# systemctl start pcsd.service
# systemctl enable pcsd.service

4.1.2. Authenticating the Cluster Nodes

The following command authenticates pcs to the pcs daemon on the nodes in the cluster.
  • The user name for the pcs administrator must be hacluster on every node. It is recommended that the password for user hacluster be the same on each node.
  • If you do not specify username or password, the system will prompt you for those parameters for each node when you execute the command.
  • If you do not specify any nodes, this command will authenticate pcs on the nodes that are specified with a pcs cluster setup command, if you have previously executed that command.
pcs cluster auth [node] [...] [-u username] [-p password]
For example, the following command authenticates user hacluster on z1.example.com for both of the nodes in the cluster that consist of z1.example.com and z2.example.com. This command prompts for the password for user hacluster on the cluster nodes.
root@z1 ~]# pcs cluster auth z1.example.com z2.example.com
Username: hacluster
Password:
z1.example.com: Authorized
z2.example.com: Authorized
Authorization tokens are stored in the file ~/.pcs/tokens (or /var/lib/pcsd/tokens).

4.1.3. Configuring and Starting the Cluster Nodes

The following command configures the cluster configuration file and syncs the configuration to the specified nodes.
  • If you specify the --start option, the command will also start the cluster services on the specified nodes. If necessary, you can also start the cluster services with a separate pcs cluster start command.
    When you create a cluster with the pcs cluster setup --start command or when you start cluster services with the pcs cluster start command, there may be a slight delay before the cluster is up and running. Before performing any subsequent actions on the cluster and its configuration, it is recommended that you use the pcs cluster status command to be sure that the cluster is up and running.
  • If you specify the --local option, the command will perform changes on the local node only.
pcs cluster setup [--start] [--local] --name cluster_ name node1 [node2] [...]
The following command starts cluster services on the specified node or nodes.
  • If you specify the --all option, the command starts cluster services on all nodes.
  • If you do not specify any nodes, cluster services are started on the local node only.
pcs cluster start [--all] [node] [...]

4.2. Configuring Timeout Values for a Cluster

When you create a cluster with the pcs cluster setup command, timeout values for the cluster are set to default values that should be suitable for most cluster configurations. If you system requires different timeout values, however, you can modify these values with the pcs cluster setup options summarized in Table 4.1, “Timeout Options”

Table 4.1. Timeout Options

OptionDescription
--token timeout Sets time in milliseconds until a token loss is declared after not receiving a token (default 1000 ms)
--join timeout sets time in milliseconds to wait for join messages (default 50 ms)
--consensus timeout sets time in milliseconds to wait for consensus to be achieved before starting a new round of member- ship configuration (default 1200 ms)
--miss_count_const count sets the maximum number of times on receipt of a token a message is checked for retransmission before a retransmission occurs (default 5 messages)
--fail_recv_const failures specifies how many rotations of the token without receiving any messages when messages should be received may occur before a new configuration is formed (default 2500 failures)
For example, the following command creates the cluster new_cluster and sets the token timeout value to 10000 milliseconds (10 seconds) and the join timeout value to 100 milliseconds.
# pcs cluster setup --name new_cluster nodeA nodeB --token 10000 --join 100

4.3. Configuring Redundant Ring Protocol (RRP)

Note

Red Hat supports the configuration of Redundant Ring Protocol (RRP) in clusters subject to the conditions described in the "Redundant Ring Protocol (RRP)" section of Support Policies for RHEL High Availability Clusters - Cluster Interconnect Network Interfaces.
When you create a cluster with the pcs cluster setup command, you can configure a cluster with Redundant Ring Protocol by specifying both interfaces for each node. When using the default udpu transport, when you specify the cluster nodes you specify the ring 0 address followed by a ',', then the ring 1 address.
For example, the following command configures a cluster named my_rrp_clusterM with two nodes, node A and node B. Node A has two interfaces, nodeA-0 and nodeA-1. Node B has two interfaces, nodeB-0 and nodeB-1. To configure these nodes as a cluster using RRP, execute the following command.
# pcs cluster setup --name my_rrp_cluster nodeA-0,nodeA-1 nodeB-0,nodeB-1 
For information on configuring RRP in a cluster that uses udp transport, see the help screen for the pcs cluster setup command.

4.4. Managing Cluster Nodes

The following sections describe the commands you use to manage cluster nodes, including commands to start and stop cluster services and to add and remove cluster nodes.

4.4.1. Stopping Cluster Services

The following command stops cluster services on the specified node or nodes. As with the pcs cluster start, the --all option stops cluster services on all nodes and if you do not specify any nodes, cluster services are stopped on the local node only.
pcs cluster stop [--all] [node] [...]
You can force a stop of cluster services on the local node with the following command, which performs a kill -9 command.
pcs cluster kill

4.4.2. Enabling and Disabling Cluster Services

Use the following command to configure the cluster services to run on startup on the specified node or nodes.
  • If you specify the --all option, the command enables cluster services on all nodes.
  • If you do not specify any nodes, cluster services are enabled on the local node only.
pcs cluster enable [--all] [node] [...]
Use the following command to configure the cluster services not to run on startup on the specified node or nodes.
  • If you specify the --all option, the command disables cluster services on all nodes.
  • If you do not specify any nodes, cluster services are disabled on the local node only.
pcs cluster disable [--all] [node] [...]

4.4.3. Adding Cluster Nodes

Note

It is highly recommended that you add nodes to existing clusters only during a production maintenance window. This allows you to perform appropriate resource and deployment testing for the new node and its fencing configuration.
Use the following procedure to add a new node to an existing cluster. In this example, the existing cluster nodes are clusternode-01.example.com, clusternode-02.example.com, and clusternode-03.example.com. The new node is newnode.example.com.
On the new node to add to the cluster, perform the following tasks.
  1. Install the cluster packages. If the cluster uses SBD, the Booth ticket manager, or a quorum device, you must manually install the respective packages (sbd, booth-site, corosync-device) on the new node as well.
    [root@newnode ~]# yum install -y pcs fence-agents-all
  2. If you are running the firewalld daemon, execute the following commands to enable the ports that are required by the Red Hat High Availability Add-On.
    # firewall-cmd --permanent --add-service=high-availability
    # firewall-cmd --add-service=high-availability
  3. Set a password for the user ID hacluster. It is recommended that you use the same password for each node in the cluster.
    [root@newnode ~]# passwd hacluster
    Changing password for user hacluster.
    New password:
    Retype new password:
    passwd: all authentication tokens updated successfully.
    
  4. Execute the following commands to start the pcsd service and to enable pcsd at system start.
    # systemctl start pcsd.service
    # systemctl enable pcsd.service
On a node in the existing cluster, perform the following tasks.
  1. Authenticate user hacluster on the new cluster node.
    [root@clusternode-01 ~]# pcs cluster auth newnode.example.com
    Username: hacluster
    Password:
    newnode.example.com: Authorized
    
  2. Add the new node to the existing cluster. This command also syncs the cluster configuration file corosync.conf to all nodes in the cluster, including the new node you are adding.
    [root@clusternode-01 ~]# pcs cluster node add newnode.example.com
On the new node to add to the cluster, perform the following tasks.
  1. Start and enable cluster services on the new node.
    [root@newnode ~]# pcs cluster start
    Starting Cluster...
    [root@newnode ~]# pcs cluster enable
  2. Ensure that you configure and test a fencing device for the new cluster node. For information on configuring fencing devices, see Chapter 5, Fencing: Configuring STONITH.

4.4.4. Removing Cluster Nodes

The following command shuts down the specified node and removes it from the cluster configuration file, corosync.conf, on all of the other nodes in the cluster. For information on removing all information about the cluster from the cluster nodes entirely, thereby destroying the cluster permanently, see Section 4.6, “Removing the Cluster Configuration”.
pcs cluster node remove node

4.4.5. Standby Mode

The following command puts the specified node into standby mode. The specified node is no longer able to host resources. Any resources currently active on the node will be moved to another node. If you specify the --all, this command puts all nodes into standby mode.
You can use this command when updating a resource's packages. You can also use this command when testing a configuration, to simulate recovery without actually shutting down a node.
pcs cluster standby node | --all
The following command removes the specified node from standby mode. After running this command, the specified node is then able to host resources. If you specify the --all, this command removes all nodes from standby mode.
pcs cluster unstandby node | --all
Note that when you execute the pcs cluster standby command, this adds constraints to the resources to prevent them from running on the indicated node. When you execute the pcs cluster unstandby command, this removes the constraints. This does not necessarily move the resources back to the indicated node; where the resources can run at that point depends on how you have configured your resources initially. For information on resource constraints, see Chapter 7, Resource Constraints.

4.5. Setting User Permissions

You can grant permission for specific users other than user hacluster to manage the cluster. There are two sets of permissions that you can grant to individual users:
  • Permissions that allow individual users to manage the cluster through the Web UI and to run pcs commands that connect to nodes over a network, as described in Section 4.5.1, “Setting Permissions for Node Access Over a Network”. Commands that connect to nodes over a network include commands to set up a cluster, or to add or remove nodes from a cluster.
  • Permissions for local users to allow read-only or read-write access to the cluster configuration, as described in Section 4.5.2, “Setting Local Permissions Using ACLs”. Commands that do not require connecting over a network include commands that edit the cluster configuration, such as those that create resources and configure constraints.
In situations where both sets of permissions have been assigned, the permissions for commands that connect over a network are applied first, and then permissions for editing the cluster configuration on the local node are applied. Most pcs commands do not require network access and in those cases the network permissions will not apply.

4.5.1. Setting Permissions for Node Access Over a Network

To grant permission for specific users to manage the cluster through the Web UI and to run pcs commands that connect to nodes over a network, add those users to the group haclient. You can then use the Web UI to grant permissions for those users, as described in Section 2.2.2, “Setting Cluster Management Permissions”.

4.5.2. Setting Local Permissions Using ACLs

As of Red Hat Enterprise Linux 7.1, you can use the pcs acl command to set permissions for local users to allow read-only or read-write access to the cluster configuration by using access control lists (ACLs). You can also configure ACLs using the pcsd Web UI, as described in Section 2.3.4, “Configuring ACLs”. By default, the root user and any user who is a member of the group haclient has full local read/write access to the cluster configuration.
Setting permissions for local users is a two step process:
  1. Execute the pcs acl role create... command to create a role which defines the permissions for that role.
  2. Assign the role you created to a user with the pcs acl user create command.
The following example procedure provides read-only access for a cluster configuration to a local user named rouser.
  1. This procedure requires that the user rouser exists on the local system and that the user rouser is a member of the group haclient.
    # adduser rouser
    # usermod -a -G haclient rouser
  2. Enable Pacemaker ACLs with the enable-acl cluster property.
    # pcs property set enable-acl=true --force 
  3. Create a role named read-only with read-only permissions for the cib.
    # pcs acl role create read-only description="Read access to cluster" read xpath /cib
  4. Create the user rouser in the pcs ACL system and assign that user the read-only role.
    # pcs acl user create rouser read-only
  5. View the current ACLs.
    # pcs acl
    User: rouser
      Roles: read-only
    Role: read-only
      Description: Read access to cluster
      Permission: read xpath /cib (read-only-read)
    
The following example procedure provides write access for a cluster configuration to a local user named wuser.
  1. This procedure requires that the user wuser exists on the local system and that the user wuser is a member of the group haclient.
    # adduser wuser
    # usermod -a -G haclient wuser
  2. Enable Pacemaker ACLs with the enable-acl cluster property.
    # pcs property set enable-acl=true --force 
  3. Create a role named write-access with write permissions for the cib.
    # pcs acl role create write-access description="Full access" write xpath /cib
  4. Create the user wuser in the pcs ACL system and assign that user the write-access role.
    # pcs acl user create wuser write-access
  5. View the current ACLs.
    # pcs acl
    User: rouser
      Roles: read-only
    User: wuser
      Roles: write-access
    Role: read-only
      Description: Read access to cluster
      Permission: read xpath /cib (read-only-read)
    Role: write-access
      Description: Full Access
      Permission: write xpath /cib (write-access-write)
    
For further information about cluster ACLs, see the help screen for the pcs acl command.

4.6. Removing the Cluster Configuration

To remove all cluster configuration files and stop all cluster services, thus permanently destroying a cluster, use the following command.

Warning

This command permanently removes any cluster configuration that has been created. It is recommended that you run pcs cluster stop before destroying the cluster.
pcs cluster destroy

4.7. Displaying Cluster Status

The following command displays the current status of the cluster and the cluster resources.
pcs status
You can display a subset of information about the current status of the cluster with the following commands.
The following command displays the status of the cluster, but not the cluster resources.
pcs cluster status
The following command displays the status of the cluster resources.
pcs status resources

4.8. Cluster Maintenance

In order to perform maintenance on the nodes of your cluster, you may need to stop or move the resources and services running on that cluster. Or you may need to stop the cluster software while leaving the services untouched. Pacemaker provides a variety of methods for performing system maintenance.
  • If you need to stop a node in a cluster while continuing to provide the services running on that cluster on another node, you can put the cluster node in standby mode. A node that is in standby mode is no longer able to host resources. Any resource currently active on the node will be moved to another node, or stopped if no other node is eligible to run the resource.
    For information on standby mode, see Section 4.4.5, “Standby Mode”.
  • If you need to move an individual resource off the node on which it is currently running without stopping that resource, you can use the pcs resource move command to move the resource to a different node. For information on the pcs resource move command, see Section 8.1, “Manually Moving Resources Around the Cluster”.
    When you execute the pcs resource move command, this adds a constraint to the resource to prevent it from running on the node on which it is currently running. When you are ready to move the resource back, you can execute the pcs resource clear or the pcs constraint delete command to remove the constraint. This does not necessarily move the resources back to the original node, however, since where the resources can run at that point depends on how you have configured your resources initially. You can relocate a resource to a specified node with the pcs resource relocate run command, as described in Section 8.1.1, “Moving a Resource from its Current Node”.
  • If you need to stop a running resource entirely and prevent the cluster from starting it again, you can use the pcs resource disable command. For information on the pcs resource disable command, see Section 8.4, “Enabling, Disabling, and Banning Cluster Resources”.
  • If you want to prevent Pacemaker from taking any action for a resource (for example, if you want to disable recovery actions while performing maintenance on the resource, or if you need to reload the /etc/sysconfig/pacemaker settings), use the pcs resource unmanage command, as described in Section 8.6, “Managed Resources”. Pacemaker Remote connection resources should never be unmanaged.
  • If you need to put the cluster in a state where no services will be started or stopped, you can set the maintenance-mode cluster property. Putting the cluster into maintenance mode automatically unmanages all resources. For information on setting cluster properties, see Table 12.1, “Cluster Properties”.
  • If you need to perform maintenance on a Pacemaker remote node, you can remove that node from the cluster by disabling the remote node resource, as described in Section 9.4.8, “System Upgrades and pacemaker_remote”.

Chapter 5. Fencing: Configuring STONITH

STONITH is an acronym for "Shoot The Other Node In The Head" and it protects your data from being corrupted by rogue nodes or concurrent access.
Just because a node is unresponsive, this does not mean it is not accessing your data. The only way to be 100% sure that your data is safe, is to fence the node using STONITH so we can be certain that the node is truly offline, before allowing the data to be accessed from another node.
STONITH also has a role to play in the event that a clustered service cannot be stopped. In this case, the cluster uses STONITH to force the whole node offline, thereby making it safe to start the service elsewhere.
For more complete general information on fencing and its importance in a Red Hat High Availability cluster, see Fencing in a Red Hat High Availability Cluster.

5.1. Available STONITH (Fencing) Agents

Use the following command to view of list of all available STONITH agents. You specify a filter, then this command displays only the STONITH agents that match the filter.
pcs stonith list [filter]

5.2. General Properties of Fencing Devices

Any cluster node can fence any other cluster node with any fence device, regardless of whether the fence resource is started or stopped. Whether the resource is started controls only the recurring monitor for the device, not whether it can be used, with the following exceptions:
  • You can disable a fencing device by running the pcs stonith disable stonith_id command. This will prevent any node from using that device
  • To prevent a specific node from using a fencing device, you can configure location constraints for the fencing resource with the pcs constraint location ... avoids command.
  • Configuring stonith-enabled=false will disable fencing altogether. Note, however, that Red Hat does not support clusters when fencing is disabled, as it is not suitable for a production environment.
Table 5.1, “General Properties of Fencing Devices” describes the general properties you can set for fencing devices. Refer to Section 5.3, “Displaying Device-Specific Fencing Options” for information on fencing properties you can set for specific fencing devices.

Note

For information on more advanced fencing configuration properties, see Section 5.8, “Additional Fencing Configuration Options”

Table 5.1. General Properties of Fencing Devices

FieldTypeDefaultDescription
pcmk_host_map string   A mapping of host names to ports numbers for devices that do not support host names. For example: node1:1;node2:2,3 tells the cluster to use port 1 for node1 and ports 2 and 3 for node2
pcmk_host_list string   A list of machines controlled by this device (Optional unless pcmk_host_check=static-list).
pcmk_host_check string dynamic-list How to determine which machines are controlled by the device. Allowed values: dynamic-list (query the device), static-list (check the pcmk_host_list attribute), none (assume every device can fence every machine)

5.3. Displaying Device-Specific Fencing Options

Use the following command to view the options for the specified STONITH agent.
pcs stonith describe stonith_agent
For example, the following command displays the options for the fence agent for APC over telnet/SSH.
# pcs stonith describe fence_apc
Stonith options for: fence_apc
  ipaddr (required): IP Address or Hostname
  login (required): Login Name
  passwd: Login password or passphrase
  passwd_script: Script to retrieve password
  cmd_prompt: Force command prompt
  secure: SSH connection
  port (required): Physical plug number or name of virtual machine
  identity_file: Identity file for ssh
  switch: Physical switch number on device
  inet4_only: Forces agent to use IPv4 addresses only
  inet6_only: Forces agent to use IPv6 addresses only
  ipport: TCP port to use for connection with device
  action (required): Fencing Action
  verbose: Verbose mode
  debug: Write debug information to given file
  version: Display version information and exit
  help: Display help and exit
  separator: Separator for CSV created by operation list
  power_timeout: Test X seconds for status change after ON/OFF
  shell_timeout: Wait X seconds for cmd prompt after issuing command
  login_timeout: Wait X seconds for cmd prompt after login
  power_wait: Wait X seconds after issuing ON/OFF
  delay: Wait X seconds before fencing is started
  retry_on: Count of attempts to retry power on

Warning

For fence agents that provide a method option, a value of cycle is unsupported and should not be specified, as it may cause data corruption.

5.4. Creating a Fencing Device

The following command creates a stonith device.
pcs stonith create stonith_id stonith_device_type [stonith_device_options]
# pcs stonith create MyStonith fence_virt pcmk_host_list=f1 op monitor interval=30s 
If you use a single fence device for several nodes, using a different port of each node, you do not need to create a device separately for each node. Instead you can use the pcmk_host_map option to define which port goes to which node. For example, the following command creates a single fencing device called myapc-west-13 that uses an APC power switch called west-apc and uses port 15 for node west-13.
# pcs stonith create myapc-west-13 fence_apc pcmk_host_list="west-13" ipaddr="west-apc" login="apc" passwd="apc" port="15"
The following example, however, uses the APC power switch named west-apc to fence nodes west-13 using port 15, west-14 using port 17, west-15 using port 18, and west-16 using port 19.
# pcs stonith create myapc fence_apc pcmk_host_list="west-13,west-14,west-15,west-16" pcmk_host_map="west-13:15;west-14:17;west-15:18;west-16:19" ipaddr="west-apc" login="apc" passwd="apc" 
After configuring a fence device, it is imperative that you test the device to ensure that it is working correctly. For information on testing fence devices, see Section 5.12, “Testing a Fence Device”.

5.5. Displaying Fencing Devices

The following command shows all currently configured fencing devices. If a stonith_id is specified, the command shows the options for that configured stonith device only. If the --full option is specified, all configured stonith options are displayed.
pcs stonith show [stonith_id] [--full]

5.6. Modifying and Deleting Fencing Devices

Use the following command to modify or add options to a currently configured fencing device.
pcs stonith update stonith_id [stonith_device_options]
Use the following command to remove a fencing device from the current configuration.
pcs stonith delete stonith_id

5.7. Managing Nodes with Fence Devices

You can fence a node manually with the following command. If you specify --off this will use the off API call to stonith which will turn the node off instead of rebooting it.
pcs stonith fence node [--off]
In a situation where no stonith device is able to fence a node even if it is no longer active, the cluster may not be able to recover the resources on the node. If this occurs, after manually ensuring that the node is powered down you can enter the following command to confirm to the cluster that the node is powered down and free its resources for recovery.

Warning

If the node you specify is not actually off, but running the cluster software or services normally controlled by the cluster, data corruption/cluster failure will occur.
pcs stonith confirm node

5.8. Additional Fencing Configuration Options

Table 5.2, “Advanced Properties of Fencing Devices” summarizes additional properties you can set for fencing devices. Note that these properties are for advanced use only.

Table 5.2. Advanced Properties of Fencing Devices

FieldTypeDefaultDescription
pcmk_host_argument string port An alternate parameter to supply instead of port. Some devices do not support the standard port parameter or may provide additional ones. Use this to specify an alternate, device-specific, parameter that should indicate the machine to be fenced. A value of none can be used to tell the cluster not to supply any additional parameters.
pcmk_reboot_action string reboot An alternate command to run instead of reboot. Some devices do not support the standard commands or may provide additional ones. Use this to specify an alternate, device-specific, command that implements the reboot action.
pcmk_reboot_timeout time 60s Specify an alternate timeout to use for reboot actions instead of stonith-timeout. Some devices need much more/less time to complete than normal. Use this to specify an alternate, device-specific, timeout for reboot actions.
pcmk_reboot_retries integer 2 The maximum number of times to retry the reboot command within the timeout period. Some devices do not support multiple connections. Operations may fail if the device is busy with another task so Pacemaker will automatically retry the operation, if there is time remaining. Use this option to alter the number of times Pacemaker retries reboot actions before giving up.
pcmk_off_action string off An alternate command to run instead of off. Some devices do not support the standard commands or may provide additional ones. Use this to specify an alternate, device-specific, command that implements the off action.
pcmk_off_timeout time 60s Specify an alternate timeout to use for off actions instead of stonith-timeout. Some devices need much more or much less time to complete than normal. Use this to specify an alternate, device-specific, timeout for off actions.
pcmk_off_retries integer 2 The maximum number of times to retry the off command within the timeout period. Some devices do not support multiple connections. Operations may fail if the device is busy with another task so Pacemaker will automatically retry the operation, if there is time remaining. Use this option to alter the number of times Pacemaker retries off actions before giving up.
pcmk_list_action string list An alternate command to run instead of list. Some devices do not support the standard commands or may provide additional ones. Use this to specify an alternate, device-specific, command that implements the list action.
pcmk_list_timeout time 60s Specify an alternate timeout to use for list actions instead of stonith-timeout. Some devices need much more or much less time to complete than normal. Use this to specify an alternate, device-specific, timeout for list actions.
pcmk_list_retries integer 2 The maximum number of times to retry the list command within the timeout period. Some devices do not support multiple connections. Operations may fail if the device is busy with another task so Pacemaker will automatically retry the operation, if there is time remaining. Use this option to alter the number of times Pacemaker retries list actions before giving up.
pcmk_monitor_action string monitor An alternate command to run instead of monitor. Some devices do not support the standard commands or may provide additional ones. Use this to specify an alternate, device-specific, command that implements the monitor action.
pcmk_monitor_timeout time 60s Specify an alternate timeout to use for monitor actions instead of stonith-timeout. Some devices need much more or much less time to complete than normal. Use this to specify an alternate, device-specific, timeout for monitor actions.
pcmk_monitor_retries integer 2 The maximum number of times to retry the monitor command within the timeout period. Some devices do not support multiple connections. Operations may fail if the device is busy with another task so Pacemaker will automatically retry the operation, if there is time remaining. Use this option to alter the number of times Pacemaker retries monitor actions before giving up.
pcmk_status_action string status An alternate command to run instead of status. Some devices do not support the standard commands or may provide additional ones. Use this to specify an alternate, device-specific, command that implements the status action.
pcmk_status_timeout time 60s Specify an alternate timeout to use for status actions instead of stonith-timeout. Some devices need much more or much less time to complete than normal. Use this to specify an alternate, device-specific, timeout for status actions.
pcmk_status_retries integer 2 The maximum number of times to retry the status command within the timeout period. Some devices do not support multiple connections. Operations may fail if the device is busy with another task so Pacemaker will automatically retry the operation, if there is time remaining. Use this option to alter the number of times Pacemaker retries status actions before giving up.
pcmk_delay_base time 0s Enable a base delay for stonith actions and specify a base delay value. This prevents double fencing when different delays are configured on the nodes. Use this to enable a static delay for stonith actions. The overall delay is derived from a random delay value adding this static delay so that the sum is kept below the maximum delay.
pcmk_delay_max time 0s Enable a random delay for stonith actions and specify the maximum of random delay. This prevents double fencing when using slow devices such as SBD. Use this to enable a random delay for stonith actions. The overall delay is derived from this random delay value adding a static delay so that the sum is kept below the maximum delay.
pcmk_action_limit integer 1 The maximum number of actions that can be performed in parallel on this device. The cluster property concurrent-fencing=true needs to be configured first. A value of -1 is unlimited.
pcmk_on_action string on For advanced use only: An alternate command to run instead of on. Some devices do not support the standard commands or may provide additional ones. Use this to specify an alternate, device-specific, command that implements the on action.
pcmk_on_timeout time 60s For advanced use only: Specify an alternate timeout to use for on actions instead of stonith-timeout. Some devices need much more or much less time to complete than normal. Use this to specify an alternate, device-specific, timeout for on actions.
pcmk_on_retries integer 2 For advanced use only: The maximum number of times to retry the on command within the timeout period. Some devices do not support multiple connections. Operations may fail if the device is busy with another task so Pacemaker will automatically retry the operation, if there is time remaining. Use this option to alter the number of times Pacemaker retries on actions before giving up.

5.9. Configuring Fencing Levels

Pacemaker supports fencing nodes with multiple devices through a feature called fencing topologies. To implement topologies, create the individual devices as you normally would and then define one or more fencing levels in the fencing topology section in the configuration.
  • Each level is attempted in ascending numeric order, starting at 1.
  • If a device fails, processing terminates for the current level. No further devices in that level are exercised and the next level is attempted instead.
  • If all devices are successfully fenced, then that level has succeeded and no other levels are tried.
  • The operation is finished when a level has passed (success), or all levels have been attempted (failed).
Use the following command to add a fencing level to a node. The devices are given as a comma-separated list of stonith ids, which are attempted for the node at that level.
pcs stonith level add level node devices
The following command lists all of the fencing levels that are currently configured.
pcs stonith level
In the following example, there are two fence devices configured for node rh7-2: an ilo fence device called my_ilo and an apc fence device called my_apc. These commands sets up fence levels so that if the device my_ilo fails and is unable to fence the node, then Pacemaker will attempt to use the device my_apc. This example also shows the output of the pcs stonith level command after the levels are configured.
# pcs stonith level add 1 rh7-2 my_ilo
# pcs stonith level add 2 rh7-2 my_apc
# pcs stonith level
 Node: rh7-2
  Level 1 - my_ilo
  Level 2 - my_apc
The following command removes the fence level for the specified node and devices. If no nodes or devices are specified then the fence level you specify is removed from all nodes.
pcs stonith level remove level [node_id] [stonith_id] ... [stonith_id]
The following command clears the fence levels on the specified node or stonith id. If you do not specify a node or stonith id, all fence levels are cleared.
pcs stonith level clear [node|stonith_id(s)]
If you specify more than one stonith id, they must be separated by a comma and no spaces, as in the following example.
# pcs stonith level clear dev_a,dev_b
The following command verifies that all fence devices and nodes specified in fence levels exist.
pcs stonith level verify
As of Red Hat Enterprise Linux 7.4, you can specify nodes in fencing topology by a regular expression applied on a node name and by a node attribute and its value. For example, the following commands configure nodes node1, node2, and `node3 to use fence devices apc1 and `apc2, and nodes `node4, node5, and `node6 to use fence devices apc3 and `apc4.
pcs stonith level add 1 "regexp%node[1-3]" apc1,apc2
pcs stonith level add 1 "regexp%node[4-6]" apc3,apc4
The following commands yield the same results by using node attribute matching.
pcs node attribute node1 rack=1
pcs node attribute node2 rack=1
pcs node attribute node3 rack=1
pcs node attribute node4 rack=2
pcs node attribute node5 rack=2
pcs node attribute node6 rack=2
pcs stonith level add 1 attrib%rack=1 apc1,apc2
pcs stonith level add 1 attrib%rack=2 apc3,apc4

5.10. Configuring Fencing for Redundant Power Supplies

When configuring fencing for redundant power supplies, the cluster must ensure that when attempting to reboot a host, both power supplies are turned off before either power supply is turned back on.
If the node never completely loses power, the node may not release its resources. This opens up the possibility of nodes accessing these resources simultaneously and corrupting them.
Prior to Red Hat Enterprise Linux 7.2, you needed to explicitly configure different versions of the devices which used either the 'on' or 'off' actions. Since Red Hat Enterprise Linux 7.2, it is now only required to define each device once and to specify that both are required to fence the node, as in the following example.
# pcs stonith create apc1 fence_apc_snmp ipaddr=apc1.example.com login=user passwd='7a4D#1j!pz864' pcmk_host_map="node1.example.com:1;node2.example.com:2"

# pcs stonith create apc2 fence_apc_snmp ipaddr=apc2.example.com login=user passwd='7a4D#1j!pz864' pcmk_host_map="node1.example.com:1;node2.example.com:2"

# pcs stonith level add 1 node1.example.com apc1,apc2
# pcs stonith level add 1 node2.example.com apc1,apc2

5.11. Configuring ACPI For Use with Integrated Fence Devices

If your cluster uses integrated fence devices, you must configure ACPI (Advanced Configuration and Power Interface) to ensure immediate and complete fencing.
If a cluster node is configured to be fenced by an integrated fence device, disable ACPI Soft-Off for that node. Disabling ACPI Soft-Off allows an integrated fence device to turn off a node immediately and completely rather than attempting a clean shutdown (for example, shutdown -h now). Otherwise, if ACPI Soft-Off is enabled, an integrated fence device can take four or more seconds to turn off a node (see the note that follows). In addition, if ACPI Soft-Off is enabled and a node panics or freezes during shutdown, an integrated fence device may not be able to turn off the node. Under those circumstances, fencing is delayed or unsuccessful. Consequently, when a node is fenced with an integrated fence device and ACPI Soft-Off is enabled, a cluster recovers slowly or requires administrative intervention to recover.

Note

The amount of time required to fence a node depends on the integrated fence device used. Some integrated fence devices perform the equivalent of pressing and holding the power button; therefore, the fence device turns off the node in four to five seconds. Other integrated fence devices perform the equivalent of pressing the power button momentarily, relying on the operating system to turn off the node; therefore, the fence device turns off the node in a time span much longer than four to five seconds.
Disabling ACPI Soft-Off with the BIOS may not be possible with some systems. If disabling ACPI Soft-Off with the BIOS is not satisfactory for your cluster, you can disable ACPI Soft-Off with one of the following alternate methods:
  • Setting HandlePowerKey=ignore in the /etc/systemd/logind.conf file and verifying that the node node turns off immediately when fenced, as described in Section 5.11.2, “Disabling ACPI Soft-Off in the logind.conf file”. This is the first alternate method of disabling ACPI Soft-Off.
  • Appending acpi=off to the kernel boot command line, as described in Section 5.11.3, “Disabling ACPI Completely in the GRUB 2 File”. This is the second alternate method of disabling ACPI Soft-Off, if the preferred or the first alternate method is not available.

    Important

    This method completely disables ACPI; some computers do not boot correctly if ACPI is completely disabled. Use this method only if the other methods are not effective for your cluster.

5.11.1. Disabling ACPI Soft-Off with the BIOS

You can disable ACPI Soft-Off by configuring the BIOS of each cluster node with the following procedure.

Note

The procedure for disabling ACPI Soft-Off with the BIOS may differ among server systems. You should verify this procedure with your hardware documentation.
  1. Reboot the node and start the BIOS CMOS Setup Utility program.
  2. Navigate to the Power menu (or equivalent power management menu).
  3. At the Power menu, set the Soft-Off by PWR-BTTN function (or equivalent) to Instant-Off (or the equivalent setting that turns off the node by means of the power button without delay). Example 5.1, “BIOS CMOS Setup Utility: Soft-Off by PWR-BTTN set to Instant-Off shows a Power menu with ACPI Function set to Enabled and Soft-Off by PWR-BTTN set to Instant-Off.

    Note

    The equivalents to ACPI Function, Soft-Off by PWR-BTTN, and Instant-Off may vary among computers. However, the objective of this procedure is to configure the BIOS so that the computer is turned off by means of the power button without delay.
  4. Exit the BIOS CMOS Setup Utility program, saving the BIOS configuration.
  5. Verify that the node turns off immediately when fenced. For information on testing a fence device, see Section 5.12, “Testing a Fence Device”.

Example 5.1. BIOS CMOS Setup Utility: Soft-Off by PWR-BTTN set to Instant-Off

+---------------------------------------------|-------------------+
|    ACPI Function             [Enabled]      |    Item Help      |
|    ACPI Suspend Type         [S1(POS)]      |-------------------|
|  x Run VGABIOS if S3 Resume   Auto          |   Menu Level   *  |
|    Suspend Mode              [Disabled]     |                   |
|    HDD Power Down            [Disabled]     |                   |
|    Soft-Off by PWR-BTTN      [Instant-Off   |                   |
|    CPU THRM-Throttling       [50.0%]        |                   |
|    Wake-Up by PCI card       [Enabled]      |                   |
|    Power On by Ring          [Enabled]      |                   |
|    Wake Up On LAN            [Enabled]      |                   |
|  x USB KB Wake-Up From S3     Disabled      |                   |
|    Resume by Alarm           [Disabled]     |                   |
|  x  Date(of Month) Alarm       0            |                   |
|  x  Time(hh:mm:ss) Alarm       0 :  0 :     |                   |
|    POWER ON Function         [BUTTON ONLY   |                   |
|  x KB Power ON Password       Enter         |                   |
|  x Hot Key Power ON           Ctrl-F1       |                   |
|                                             |                   |
|                                             |                   |
+---------------------------------------------|-------------------+
This example shows ACPI Function set to Enabled, and Soft-Off by PWR-BTTN set to Instant-Off.

5.11.2. Disabling ACPI Soft-Off in the logind.conf file

To disable power-key handing in the /etc/systemd/logind.conf file, use the following procedure.
  1. Define the following configuration in the /etc/systemd/lodingd.conf file:
    HandlePowerKey=ignore
    
  2. Reload the systemd configuration:
    # systemctl daemon-reload
  3. Verify that the node turns off immediately when fenced. For information on testing a fence device, see Section 5.12, “Testing a Fence Device”.

5.11.3. Disabling ACPI Completely in the GRUB 2 File

You can disable ACPI Soft-Off by appending acpi=off to the GRUB menu entry for a kernel.

Important

This method completely disables ACPI; some computers do not boot correctly if ACPI is completely disabled. Use this method only if the other methods are not effective for your cluster.
Use the following procedure to disable ACPI in the GRUB 2 file:
  1. Use the --args option in combination with the --update-kernel option of the grubby tool to change the grub.cfg file of each cluster node as follows:
    # grubby --args=acpi=off --update-kernel=ALL
    For general information on GRUB 2, see the Working with GRUB 2 chapter in the System Administrator's Guide.
  2. Reboot the node.
  3. Verify that the node turns off immediately when fenced. For information on testing a fence device, see Section 5.12, “Testing a Fence Device”.

5.12. Testing a Fence Device

Fencing is a fundamental part of the Red Hat Cluster infrastructure and it is therefore important to validate or test that fencing is working properly.
Use the following procedure to test a fence device.
  1. Use ssh, telnet, HTTP, or whatever remote protocol is used to connect to the device to manually log in and test the fence device or see what output is given. For example, if you will be configuring fencing for an IPMI-enabled device, then try to log in remotely with ipmitool. Take note of the options used when logging in manually because those options might be needed when using the fencing agent.
    If you are unable to log in to the fence device, verify that the device is pingable, there is nothing such as a firewall configuration that is preventing access to the fence device, remote access is enabled on the fencing agent, and the credentials are correct.
  2. Run the fence agent manually, using the fence agent script. This does not require that the cluster services are running, so you can perform this step before the device is configured in the cluster. This can ensure that the fence device is responding properly before proceeding.

    Note

    The examples in this section use the fence_ilo fence agent script for an iLO device. The actual fence agent you will use and the command that calls that agent will depend on your server hardware. You should consult the man page for the fence agent you are using to determine which options to specify. You will usually need to know the login and password for the fence device and other information related to the fence device.
    The following example shows the format you would use to run the fence_ilo fence agent script with -o status parameter to check the status of the fence device interface on another node without actually fencing it. This allows you to test the device and get it working before attempting to reboot the node. When running this command, you specify the name and password of an iLO user that has power on and off permissions for the iLO device.
    # fence_ilo -a ipaddress -l username -p password -o status
    The following example shows the format you would use to run the fence_ilo fence agent script with the -o reboot parameter. Running this command on one node reboots another node on which you have configured the fence agent.
    # fence_ilo -a ipaddress -l username -p password -o reboot
    If the fence agent failed to properly do a status, off, on, or reboot action, you should check the hardware, the configuration of the fence device, and the syntax of your commands. In addition, you can run the fence agent script with the debug output enabled. The debug output is useful for some fencing agents to see where in the sequence of events the fencing agent script is failing when logging into the fence device.
    # fence_ilo -a ipaddress -l username -p password -o status -D /tmp/$(hostname)-fence_agent.debug
    When diagnosing a failure that has occurred, you should ensure that the options you specified when manually logging in to the fence device are identical to what you passed on to the fence agent with the fence agent script.
    For fence agents that support an encrypted connection, you may see an error due to certificate validation failing, requiring that you trust the host or that you use the fence agent's ssl-insecure parameter. Similarly, if SSL/TLS is disabled on the target device, you may need to account for this when setting the SSL parameters for the fence agent.

    Note

    If the fence agent that is being tested is a fence_drac, fence_ilo, or some other fencing agent for a systems management device that continues to fail, then fall back to trying fence_ipmilan. Most systems management cards support IPMI remote login and the only supported fencing agent is fence_ipmilan.
  3. Once the fence device has been configured in the cluster with the same options that worked manually and the cluster has been started, test fencing with the pcs stonith fence command from any node (or even multiple times from different nodes), as in the following example. The pcs stonith fence command reads the cluster configuration from the CIB and calls the fence agent as configured to execute the fence action. This verifies that the cluster configuration is correct.
    # pcs stonith fence node_name
    If the pcs stonith fence command works properly, that means the fencing configuration for the cluster should work when a fence event occurs. If the command fails, it means that cluster management cannot invoke the fence device through the configuration it has retrieved. Check for the following issues and update your cluster configuration as needed.
    • Check your fence configuration. For example, if you have used a host map you should ensure that the system can find the node using the host name you have provided.
    • Check whether the password and user name for the device include any special characters that could be misinterpreted by the bash shell. Making sure that you enter passwords and user names surrounded by quotation marks could address this issue.
    • Check whether you can connect to the device using the exact IP address or host name you specified in the pcs stonith command. For example, if you give the host name in the stonith command but test by using the IP address, that is not a valid test.
    • If the protocol that your your fence device uses is accessible to you, use that protocol to try to connect to the device. For example many agents use ssh or telnet. You should try to connect to the device with the credentials you provided when configuring the device, to see if you get a valid prompt and can log in to the device.
    If you determine that all your parameters are appropriate but you still have trouble connecting to your fence device, you can check the logging on the fence device itself, if the device provides that, which will show if the user has connected and what command the user issued. You can also search through the /var/log/messages file for instances of stonith and error, which could give some idea of what is transpiring, but some agents can provide additional information.
  4. Once the fence device tests are working and the cluster is up and running, test an actual failure. To do this, take an action in the cluster that should initiate a token loss.
    • Take down a network. How you take a network depends on your specific configuration. In many cases, you can physically pull the network or power cables out of the host.

      Note

      Disabling the network interface on the local host rather than physically disconnecting the network or power cables is not recommended as a test of fencing because it does not accurately simulate a typical real-world failure.
    • Block corosync traffic both inbound and outbound using the local firewall.
      The following example blocks corosync, assuming the default corosync port is used, firewalld is used as the local firewall, and the network interface used by corosync is in the default firewall zone:
      # firewall-cmd --direct --add-rule ipv4 filter OUTPUT 2 -p udp --dport=5405 -j DROP
      # firewall-cmd --add-rich-rule='rule family="ipv4" port port="5405" protocol="udp" drop'
    • Simulate a crash and panic your machine with sysrq-trigger. Note, however, that triggering a kernel panic can cause data loss; it is recommended that you disable your cluster resources first.
      # echo c > /proc/sysrq-trigger

Chapter 6. Configuring Cluster Resources

This chapter provides information on configuring resources in a cluster.

6.1. Resource Creation

Use the following command to create a cluster resource.
pcs resource create resource_id [standard:[provider:]]type [resource_options] [op operation_action operation_options [operation_action operation options]...] [meta meta_options...] [clone [clone_options] | master [master_options] | --group group_name [--before resource_id | --after resource_id] | [bundle bundle_id] [--disabled] [--wait[=n]]
When you specify the --group option, the resource is added to the resource group named. If the group does not exist, this creates the group and adds this resource to the group. For information on resource groups, see Section 6.5, “Resource Groups”.
The --before and --after options specify the position of the added resource relative to a resource that already exists in a resource group.
Specifying the --disabled option indicates that the resource is not started automatically.
The following command creates a resource with the name VirtualIP of standard ocf, provider heartbeat, and type IPaddr2. The floating address of this resource is 192.168.0.120, the system will check whether the resource is running every 30 seconds.
# pcs resource create VirtualIP ocf:heartbeat:IPaddr2 ip=192.168.0.120 cidr_netmask=24 op monitor interval=30s
Alternately, you can omit the standard and provider fields and use the following command. This will default to a standard of ocf and a provider of heartbeat.
# pcs resource create VirtualIP IPaddr2 ip=192.168.0.120 cidr_netmask=24 op monitor interval=30s
Use the following command to delete a configured resource.
pcs resource delete resource_id
For example, the following command deletes an existing resource with a resource ID of VirtualIP
# pcs resource delete VirtualIP

6.2. Resource Properties

The properties that you define for a resource tell the cluster which script to use for the resource, where to find that script and what standards it conforms to. Table 6.1, “Resource Properties” describes these properties.

Table 6.1. Resource Properties

FieldDescription
resource_id
Your name for the resource
standard
The standard the script conforms to. Allowed values: ocf, service, upstart, systemd, lsb, stonith
type
The name of the Resource Agent you wish to use, for example IPaddr or Filesystem
provider
The OCF spec allows multiple vendors to supply the same resource agent. Most of the agents shipped by Red Hat use heartbeat as the provider.
Table 6.2, “Commands to Display Resource Properties”. summarizes the commands that display the available resource properties.

Table 6.2. Commands to Display Resource Properties

pcs Display Command Output
pcs resource list Displays a list of all available resources.
pcs resource standards Displays a list of available resources agent standards.
pcs resource providers Displays a list of available resources agent providers.
pcs resource list string Displays a list of available resources filtered by the specified string. You can use this command to display resources filtered by the name of a standard, a provider, or a type.

6.3. Resource-Specific Parameters

For any individual resource, you can use the following command to display the parameters you can set for that resource.
# pcs resource describe standard:provider:type|type
For example, the following command displays the parameters you can set for a resource of type LVM.
# pcs resource describe LVM
Resource options for: LVM
  volgrpname (required): The name of volume group.
  exclusive: If set, the volume group will be activated exclusively.
  partial_activation: If set, the volume group will be activated even
  only partial of the physical volumes available. It helps to set to
  true, when you are using mirroring logical volumes.

6.4. Resource Meta Options

In addition to the resource-specific parameters, you can configure additional resource options for any resource. These options are used by the cluster to decide how your resource should behave. Table 6.3, “Resource Meta Options” describes these options.

Table 6.3. Resource Meta Options

FieldDefaultDescription
priority
0
If not all resources can be active, the cluster will stop lower priority resources in order to keep higher priority ones active.
target-role
Started
What state should the cluster attempt to keep this resource in? Allowed values:
* Stopped - Force the resource to be stopped
* Started - Allow the resource to be started (In the case of multistate resources, they will not promoted to master)
* Master - Allow the resource to be started and, if appropriate, promoted
is-managed
true
Is the cluster allowed to start and stop the resource? Allowed values: true, false
resource-stickiness
0
Value to indicate how much the resource prefers to stay where it is.
requires
Calculated
Indicates under what conditions the resource can be started.
Defaults to fencing except under the conditions noted below. Possible values:
* nothing - The cluster can always start the resource.
* quorum - The cluster can only start this resource if a majority of the configured nodes are active. This is the default value if stonith-enabled is false or the resource's standard is stonith.
* fencing - The cluster can only start this resource if a majority of the configured nodes are active and any failed or unknown nodes have been powered off.
* unfencing - The cluster can only start this resource if a majority of the configured nodes are active and any failed or unknown nodes have been powered off and only on nodes that have been unfenced. This is the default value if the provides=unfencing stonith meta option has been set for a fencing device.
migration-threshold
INFINITY
How many failures may occur for this resource on a node, before this node is marked ineligible to host this resource. A value of 0 indicates that this feature is disabled (the node will never be marked ineligible); by contrast, the cluster treats INFINITY (the default) as a very large but finite number. This option has an effect only if the failed operation has on-fail=restart (the default), and additionally for failed start operations if the cluster property start-failure-is-fatal is false. For information on configuring the migration-threshold option, see Section 8.2, “Moving Resources Due to Failure”. For information on the start-failure-is-fatal option, see Table 12.1, “Cluster Properties”.
failure-timeout
0 (disabled)
Used in conjunction with the migration-threshold option, indicates how many seconds to wait before acting as if the failure had not occurred, and potentially allowing the resource back to the node on which it failed. For information on configuring the failure-timeout option, see Section 8.2, “Moving Resources Due to Failure”.
multiple-active
stop_start
What should the cluster do if it ever finds the resource active on more than one node. Allowed values:
* block - mark the resource as unmanaged
* stop_only - stop all active instances and leave them that way
* stop_start - stop all active instances and start the resource in one location only
To change the default value of a resource option, use the following command.
pcs resource defaults options
For example, the following command resets the default value of resource-stickiness to 100.
# pcs resource defaults resource-stickiness=100
Omitting the options parameter from the pcs resource defaults displays a list of currently configured default values for resource options. The following example shows the output of this command after you have reset the default value of resource-stickiness to 100.
# pcs resource defaults
resource-stickiness:100
Whether you have reset the default value of a resource meta option or not, you can set a resource option for a particular resource to a value other than the default when you create the resource. The following shows the format of the pcs resource create command you use when specifying a value for a resource meta option.
pcs resource create resource_id standard:provider:type|type [resource options] [meta meta_options...]
For example, the following command creates a resource with a resource-stickiness value of 50.
# pcs resource create VirtualIP ocf:heartbeat:IPaddr2 ip=192.168.0.120 cidr_netmask=24 meta resource-stickiness=50
You can also set the value of a resource meta option for an existing resource, group, cloned resource, or master resource with the following command.
pcs resource meta resource_id | group_id | clone_id | master_id  meta_options
In the following example, there is an existing resource named dummy_resource. This command sets the failure-timeout meta option to 20 seconds, so that the resource can attempt to restart on the same node in 20 seconds.
# pcs resource meta dummy_resource failure-timeout=20s 
After executing this command, you can display the values for the resource to verity that failure-timeout=20s is set.
# pcs resource show dummy_resource
 Resource: dummy_resource (class=ocf provider=heartbeat type=Dummy)
  Meta Attrs: failure-timeout=20s
  Operations: start interval=0s timeout=20 (dummy_resource-start-timeout-20)
              stop interval=0s timeout=20 (dummy_resource-stop-timeout-20)
              monitor interval=10 timeout=20 (dummy_resource-monitor-interval-10)
For information on resource clone meta options, see Section 9.1, “Resource Clones”. For information on resource master meta options, see Section 9.2, “Multistate Resources: Resources That Have Multiple Modes”.

6.5. Resource Groups

One of the most common elements of a cluster is a set of resources that need to be located together, start sequentially, and stop in the reverse order. To simplify this configuration, Pacemaker supports the concept of groups.
You create a resource group with the following command, specifying the resources to include in the group. If the group does not exist, this command creates the group. If the group exists, this command adds additional resources to the group. The resources will start in the order you specify them with this command, and will stop in the reverse order of their starting order.
pcs resource group add group_name resource_id [resource_id] ... [resource_id]
[--before resource_id | --after resource_id
You can use the --before and --after options of this command to specify the position of the added resources relative to a resource that already exists in the group.
You can also add a new resource to an existing group when you create the resource, using the following command. The resource you create is added to the group named group_name.
pcs resource create resource_id standard:provider:type|type [resource_options] [op operation_action operation_options] --group group_name
You remove a resource from a group with the following command. If there are no resources in the group, this command removes the group itself.
pcs resource group remove group_name resource_id...
The following command lists all currently configured resource groups.
pcs resource group list
The following example creates a resource group named shortcut that contains the existing resources IPaddr and Email.
# pcs resource group add shortcut IPaddr Email
There is no limit to the number of resources a group can contain. The fundamental properties of a group are as follows.
  • Resources are started in the order in which you specify them (in this example, IPaddr first, then Email).
  • Resources are stopped in the reverse order in which you specify them. (Email first, then IPaddr).
If a resource in the group cannot run anywhere, then no resource specified after that resource is allowed to run.
  • If IPaddr cannot run anywhere, neither can Email.
  • If Email cannot run anywhere, however, this does not affect IPaddr in any way.
Obviously as the group grows bigger, the reduced configuration effort of creating resource groups can become significant.

6.5.1. Group Options

A resource group inherits the following options from the resources that it contains: priority, target-role, is-managed For information on resource options, see Table 6.3, “Resource Meta Options”.

6.5.2. Group Stickiness

Stickiness, the measure of how much a resource wants to stay where it is, is additive in groups. Every active resource of the group will contribute its stickiness value to the group’s total. So if the default resource-stickiness is 100, and a group has seven members, five of which are active, then the group as a whole will prefer its current location with a score of 500.

6.6. Resource Operations

To ensure that resources remain healthy, you can add a monitoring operation to a resource's definition. If you do not specify a monitoring operation for a resource, by default the pcs command will create a monitoring operation, with an interval that is determined by the resource agent. If the resource agent does not provide a default monitoring interval, the pcs command will create a monitoring operation with an interval of 60 seconds.
Table 6.4, “Properties of an Operation” summarizes the properties of a resource monitoring operation.

Table 6.4. Properties of an Operation

FieldDescription
id
Unique name for the action. The system assigns this when you configure an operation.
name
The action to perform. Common values: monitor, start, stop
interval
If set to a nonzero value, a recurring operation is created that repeats at this frequency, in seconds. A nonzero value makes sense only when the action name is set to monitor. A recurring monitor action will be executed immediately after a resource start completes, and subsequent monitor actions are scheduled starting at the time the previous monitor action completed. For example, if a monitor action with interval=20s is executed at 01:00:00, the next monitor action does not occur at 01:00:20, but at 20 seconds after the first monitor action completes.
If set to zero, which is the default value, this parameter allows you to provide values to be used for operations created by the cluster. For example, if the interval is set to zero, the name of the operation is set to start, and the timeout value is set to 40, then Pacemaker will use a timeout of 40 seconds when starting this resource. A monitor operation with a zero interval allows you to set the timeout/on-fail/enabled values for the probes that Pacemaker does at startup to get the current status of all resources when the defaults are not desirable.
timeout
If the operation does not complete in the amount of time set by this parameter, abort the operation and consider it failed. The default value is the value of timeout if set with the pcs resource op defaults command, or 20 seconds if it is not set. If you find that your system includes a resource that requires more time than the system allows to perform an operation (such as start, stop, or monitor), investigate the cause and if the lengthy execution time is expected you can increase this value.
The timeout value is not a delay of any kind, nor does the cluster wait the entire timeout period if the operation returns before the timeout period has completed.
on-fail
The action to take if this action ever fails. Allowed values:
* ignore - Pretend the resource did not fail
* block - Do not perform any further operations on the resource
* stop - Stop the resource and do not start it elsewhere
* restart - Stop the resource and start it again (possibly on a different node)
* fence - STONITH the node on which the resource failed
* standby - Move all resources away from the node on which the resource failed
The default for the stop operation is fence when STONITH is enabled and block otherwise. All other operations default to restart.
enabled
If false, the operation is treated as if it does not exist. Allowed values: true, false

6.6.1. Configuring Resource Operations

You can configure monitoring operations when you create a resource, using the following command.
pcs resource create resource_id standard:provider:type|type [resource_options] [op operation_action operation_options [operation_type operation_options]...]
For example, the following command creates an IPaddr2 resource with a monitoring operation. The new resource is called VirtualIP with an IP address of 192.168.0.99 and a netmask of 24 on eth2. A monitoring operation will be performed every 30 seconds.
# pcs resource create VirtualIP ocf:heartbeat:IPaddr2 ip=192.168.0.99 cidr_netmask=24 nic=eth2 op monitor interval=30s
Alternately, you can add a monitoring operation to an existing resource with the following command.
pcs resource op add resource_id operation_action [operation_properties]
Use the following command to delete a configured resource operation.
pcs resource op remove resource_id operation_name operation_properties

Note

You must specify the exact operation properties to properly remove an existing operation.
To change the values of a monitoring option, you can update the resource. For example, you can create a VirtualIP with the following command.
# pcs resource create VirtualIP ocf:heartbeat:IPaddr2 ip=192.168.0.99 cidr_netmask=24 nic=eth2
By default, this command creates these operations.
Operations: start interval=0s timeout=20s (VirtualIP-start-timeout-20s)
            stop interval=0s timeout=20s (VirtualIP-stop-timeout-20s)
            monitor interval=10s timeout=20s (VirtualIP-monitor-interval-10s)
To change the stop timeout operation, execute the following command.
# pcs resource update VirtualIP op stop interval=0s timeout=40s

# pcs resource show VirtualIP
 Resource: VirtualIP (class=ocf provider=heartbeat type=IPaddr2)
  Attributes: ip=192.168.0.99 cidr_netmask=24 nic=eth2
  Operations: start interval=0s timeout=20s (VirtualIP-start-timeout-20s)
              monitor interval=10s timeout=20s (VirtualIP-monitor-interval-10s)
              stop interval=0s timeout=40s (VirtualIP-name-stop-interval-0s-timeout-40s)

6.6.2. Configuring Global Resource Operation Defaults

You can use the following command to set global default values for monitoring operations.
pcs resource op defaults [options]
For example, the following command sets a global default of a timeout value of 240 seconds for all monitoring operations.
# pcs resource op defaults timeout=240s
To display the currently configured default values for monitoring operations, do not specify any options when you execute the pcs resource op defaults command.
For example, following command displays the default monitoring operation values for a cluster which has been configured with a timeout value of 240 seconds.
# pcs resource op defaults
timeout: 240s
Note that a cluster resource will use the global default only when the option is not specified in the cluster resource definition. By default, resource agents define the timeout option for all operations. For the global operation timeout value to be honored, you must create the cluster resource without the timeout option explicitly or you must remove the timeout option by updating the cluster resource, as in the following command.
# pcs resource update VirtualIP op monitor interval=10s
For example, after setting a global default of a timeout value of 240 seconds for all monitoring operations and updating the cluster resource VirtualIP to remove the timeout value for the monitor operation, the resource VirtualIP will then have timeout values for start, stop, and monitor operations of 20s, 40s and 240s, respectively. The global default value for timeout operations is applied here only on the monitor operation, where the default timeout option was removed by the previous command.
# pcs resource show VirtualIP
 Resource: VirtualIP (class=ocf provider=heartbeat type=IPaddr2)
   Attributes: ip=192.168.0.99 cidr_netmask=24 nic=eth2
   Operations: start interval=0s timeout=20s (VirtualIP-start-timeout-20s)
               monitor interval=10s (VirtualIP-monitor-interval-10s)
               stop interval=0s timeout=40s (VirtualIP-name-stop-interval-0s-timeout-40s)

6.7. Displaying Configured Resources

To display a list of all configured resources, use the following command.
pcs resource show
For example, if your system is configured with a resource named VirtualIP and a resource named WebSite, the pcs resource show command yields the following output.
# pcs resource show
 VirtualIP	(ocf::heartbeat:IPaddr2):	Started 
 WebSite	(ocf::heartbeat:apache):	Started
To display a list of all configured resources and the parameters configured for those resources, use the --full option of the pcs resource show command, as in the following example.
# pcs resource show --full
 Resource: VirtualIP (type=IPaddr2 class=ocf provider=heartbeat)
  Attributes: ip=192.168.0.120 cidr_netmask=24 
  Operations: monitor interval=30s
 Resource: WebSite (type=apache class=ocf provider=heartbeat)
  Attributes: statusurl=http://localhost/server-status configfile=/etc/httpd/conf/httpd.conf 
  Operations: monitor interval=1min
To display the configured parameters for a resource, use the following command.
pcs resource show resource_id
For example, the following command displays the currently configured parameters for resource VirtualIP.
# pcs resource show VirtualIP
 Resource: VirtualIP (type=IPaddr2 class=ocf provider=heartbeat)
  Attributes: ip=192.168.0.120 cidr_netmask=24
  Operations: monitor interval=30s

6.8. Modifying Resource Parameters

To modify the parameters of a configured resource, use the following command.
pcs resource update resource_id [resource_options]
The following sequence of commands show the initial values of the configured parameters for resource VirtualIP, the command to change the value of the ip parameter, and the values following the update command.
# pcs resource show VirtualIP
 Resource: VirtualIP (type=IPaddr2 class=ocf provider=heartbeat)
  Attributes: ip=192.168.0.120 cidr_netmask=24
  Operations: monitor interval=30s
# pcs resource update VirtualIP ip=192.169.0.120
# pcs resource show VirtualIP
 Resource: VirtualIP (type=IPaddr2 class=ocf provider=heartbeat)
  Attributes: ip=192.169.0.120 cidr_netmask=24
  Operations: monitor interval=30s

6.9. Multiple Monitoring Operations

You can configure a single resource with as many monitor operations as a resource agent supports. In this way you can do a superficial health check every minute and progressively more intense ones at higher intervals.

Note

When configuring multiple monitor operations, you must ensure that no two operations are performed at the same interval.
To configure additional monitoring operations for a resource that supports more in-depth checks at different levels, you add an OCF_CHECK_LEVEL=n option.
For example, if you configure the following IPaddr2 resource, by default this creates a monitoring operation with an interval of 10 seconds and a timeout value of 20 seconds.
# pcs resource create VirtualIP ocf:heartbeat:IPaddr2 ip=192.168.0.99 cidr_netmask=24 nic=eth2 
If the Virtual IP supports a different check with a depth of 10, the following command causes Pacemaker to perform the more advanced monitoring check every 60 seconds in addition to the normal Virtual IP check every 10 seconds. (As noted, you should not configure the additional monitoring operation with a 10-second interval as well.)
# pcs resource op add VirtualIP monitor interval=60s OCF_CHECK_LEVEL=10

6.10. Enabling and Disabling Cluster Resources

The following command enables the resource specified by resource_id.
pcs resource enable resource_id
The following command disables the resource specified by resource_id.
pcs resource disable resource_id

6.11. Cluster Resources Cleanup

If a resource has failed, a failure message appears when you display the cluster status. If you resolve that resource, you can clear that failure status with the pcs resource cleanup command. This command resets the resource status and failcount, telling the cluster to forget the operation history of a resource and re-detect its current state.
The following command cleans up the resource specified by resource_id.
pcs resource cleanup resource_id
If you do not specify a resource_id, this command resets the resource status and failcountfor all resources.
As of Red Hat Enterprise Linux 7.5, the pcs resource cleanup command probes only the resources that display as a failed action. To probe all resources on all nodes you can enter the following command:
pcs resource refresh
By default, the pcs resource refresh command probes only the nodes where a resource's state is known. To probe all resources even if the state is not known, enter the following command:
pcs resource refresh --full

Chapter 7. Resource Constraints

You can determine the behavior of a resource in a cluster by configuring constraints for that resource. You can configure the following categories of constraints:
As a shorthand for configuring a set of constraints that will locate a set of resources together and ensure that the resources start sequentially and stop in reverse order, Pacemaker supports the concept of resource groups. For information on resource groups, see Section 6.5, “Resource Groups”.

7.1. Location Constraints

Location constraints determine which nodes a resource can run on. You can configure location constraints to determine whether a resource will prefer or avoid a specified node.

7.1.1. Basic Location Constraints

You can configure a basic location constraint to specify whether a resource prefers or avoid a node, with an optional score value to indicate the relative degree of preference for the constraint.
The following command creates a location constraint for a resource to prefer the specified node or nodes. Note that it is possible to create constraints on a particular resource for more than one node with a single command.
pcs constraint location rsc prefers node[=score] [node[=score]] ...
The following command creates a location constraint for a resource to avoid the specified node or nodes.
pcs constraint location rsc avoids node[=score] [node[=score]] ...
Table 7.1, “Simple Location Constraint Options” summarizes the meanings of the options for configuring location constraints in their simplest form.

Table 7.1. Simple Location Constraint Options

FieldDescription
rsc
A resource name
node
A node’s name
score
Postive integer value to indicate the preference for whether a resource should prefer or avoid a node. INFINITY is the default score value for a resource location constraint.
A value of INFINITY for score in a command that configures a resource to prefer a node indicates that the resource will prefer that node if the node is available, but does not prevent the resource from running on another node if the specified node is unavailable. A value of INFINITY in a command that configures a resource to avoid a node indicates that the resource will never run on that node, even if no other node is available.
The following command creates a location constraint to specify that the resource Webserver prefers node node1.
# pcs constraint location Webserver prefers node1
As of Red Hat Enterprise Linux 7.4, pcs supports regular expressions in location constraints on the command line. These constraints apply to multiple resources based on the regular expression matching resource name. This allows you to configure multiple location contraints with a single command line.
The following command creates a location constraint to specify that resources dummy0 to dummy9 prefer node1.
# pcs constraint location 'regexp%dummy[0-9]' prefers node1
Since Pacemaker uses POSIX extended regular expressions as documented at http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap09.html#tag_09_04, you can specify the same constraint with the following command.
# pcs constraint location 'regexp%dummy[[:digit:]]' prefers node1

7.1.2. Advanced Location Constraints

When configuring a location constraint on a node, you can use the resource-discovery option of the pcs constraint location command to indicate a preference for whether Pacemaker should perform resource discovery on this node for the specified resource. Limiting resource discovery to a subset of nodes the resource is physically capable of running on can significantly boost performance when a large set of nodes is present. When pacemaker_remote is in use to expand the node count into the hundreds of nodes range, this option should be considered.
The following command shows the format for specifying the resource-discovery option of the pcs constraint location command. Note that id is the constraint id. The meanings of rsc, node, and score are summarized in Table 7.1, “Simple Location Constraint Options”. In this command, a positive value for score corresponds to a basic location`constraint that configures a resource to prefer a node, while a negative value for score corresponds to a basic location`constraint that configures a resource to avoid a node. As with basic location constraints, you can use regular expressions for resources with these constraints as well.
pcs constraint location add id rsc node score [resource-discovery=option]
Table 7.2, “Resource Discovery Values” summarizes the meanings of the values you can specify for the resource-discovery option.

Table 7.2. Resource Discovery Values

ValueDescription
always
Always perform resource discovery for the specified resource on this node. This is the default resource-discovery value for a resource location constraint.
never
Never perform resource discovery for the specified resource on this node.
exclusive
Perform resource discovery for the specified resource only on this node (and other nodes similarly marked as exclusive). Multiple location constraints using exclusive discovery for the same resource across different nodes creates a subset of nodes resource-discovery is exclusive to. If a resource is marked for exclusive discovery on one or more nodes, that resource is only allowed to be placed within that subset of nodes.
Note that setting the resource-discovery option to never or exclusive allows the possibility for the resource to be active in those locations without the cluster’s knowledge. This can lead to the resource being active in more than one location if the service is started outside the cluster's control (for example, by systemd or by an administrator). This can also occur if the resource-discovery property is changed while part of the cluster is down or suffering split-brain, or if the resource-discovery property is changed for a resource and node while the resource is active on that node. For this reason, using this option is appropriate only when you have more than eight nodes and there is a way to guarantee that the resource can run only in a particular location (for example, when the required software is not installed anywhere else).

7.1.3. Using Rules to Determine Resource Location

For more complicated location constraints, you can use Pacemaker rules to determine a resource's location. For general information about Pacemaker rules and the properties you can set, see Chapter 11, Pacemaker Rules.
Use the following command to configure a Pacemaker constraint that uses rules. If score is omitted, it defaults to INFINITY. If resource-discovery is omitted, it defaults to always. For information on the resource-discovery option, see Section 7.1.2, “Advanced Location Constraints”. As with basic location constraints, you can use regular expressions for resources with these constraints as well.
When using rules to configure location constraints, the value of score can be positive or negative, with a positive value indicating "prefers" and a negative value indicating "avoids".
pcs constraint location rsc rule [resource-discovery=option] [role=master|slave] [score=score | score-attribute=attribute] expression
The expression option can be one of the following where duration_options and date_spec_options are: hours, monthdays, weekdays, yeardays, months, weeks, years, weekyears, moon as described in Table 11.5, “Properties of a Date Specification”.
  • defined|not_defined attribute
  • attribute lt|gt|lte|gte|eq|ne [string|integer|version] value
  • date gt|lt date
  • date in-range date to date
  • date in-range date to duration duration_options ...
  • date-spec date_spec_options
  • expression and|or expression
  • (expression)
The following location constraint configures an expression that is true if now is any time in the year 2018.
# pcs constraint location Webserver rule score=INFINITY date-spec years=2018 
The following command configures an expression that is true from 9 am to 5 pm, Monday through Friday. Note that the hours value of 16 matches up to 16:59:59, as the numeric value (hour) still matches.
# pcs constraint location Webserver rule score=INFINITY date-spec hours="9-16" weekdays="1-5"
The following command configures an expression that is true when there is a full moon on Friday the thirteenth.
# pcs constraint location Webserver rule date-spec weekdays=5 monthdays=13 moon=4

7.1.4. Location Constraint Strategy

Using any of the location constraints described in Section 7.1.1, “Basic Location Constraints”, Section 7.1.2, “Advanced Location Constraints”, and Section 7.1.3, “Using Rules to Determine Resource Location” you can configure a general strategy for specifying which nodes a resources can run on:
  • Opt-In Clusters — Configure a cluster in which, by default, no resource can run anywhere and then selectively enable allowed nodes for specific resources. The procedure for configuring an opt-in cluster is described in Section 7.1.4.1, “Configuring an "Opt-In" Cluster”.
  • Opt-Out Clusters — Configure a cluster in which, by default, all resources can run anywhere and then create location constraints for resources that are not allowed to run on specific nodes. The procedure for configuring an opt-out cluster is described in Section 7.1.4.2, “Configuring an "Opt-Out" Cluster”. This is the default Pacemaker strategy.
Whether you should choose to configure your cluster as an opt-in or opt-out cluster depends both on your personal preference and the make-up of your cluster. If most of your resources can run on most of the nodes, then an opt-out arrangement is likely to result in a simpler configuration. On the other hand, if most resources can only run on a small subset of nodes an opt-in configuration might be simpler.

7.1.4.1. Configuring an "Opt-In" Cluster

To create an opt-in cluster, set the symmetric-cluster cluster property to false to prevent resources from running anywhere by default.
# pcs property set symmetric-cluster=false
Enable nodes for individual resources. The following commands configure location constraints so that the resource Webserver prefers node example-1, the resource Database prefers node example-2, and both resources can fail over to node example-3 if their preferred node fails. When configuring location constraints for an opt-in cluster, setting a score of zero allows a resource to run on a node without indicating any preference to prefer or avoid the node.
# pcs constraint location Webserver prefers example-1=200
# pcs constraint location Webserver prefers example-3=0
# pcs constraint location Database prefers example-2=200
# pcs constraint location Database prefers example-3=0

7.1.4.2. Configuring an "Opt-Out" Cluster

To create an opt-out cluster, set the symmetric-cluster cluster property to true to allow resources to run everywhere by default.
# pcs property set symmetric-cluster=true
The following commands will then yield a configuration that is equivalent to the example in Section 7.1.4.1, “Configuring an "Opt-In" Cluster”. Both resources can fail over to node example-3 if their preferred node fails, since every node has an implicit score of 0.
# pcs constraint location Webserver prefers example-1=200
# pcs constraint location Webserver avoids example-2=INFINITY
# pcs constraint location Database avoids example-1=INFINITY
# pcs constraint location Database prefers example-2=200
Note that it is not necessary to specify a score of INFINITY in these commands, since that is the default value for the score.

7.2. Order Constraints

Order constraints determine the order in which the resources run.
Use the following command to configure an order constraint.
pcs constraint order [action] resource_id then [action] resource_id [options]
Table 7.3, “Properties of an Order Constraint”. summarizes the properties and options for configuring order constraints.

Table 7.3. Properties of an Order Constraint

FieldDescription
resource_id
The name of a resource on which an action is performed.
action
The action to perform on a resource. Possible values of the action property are as follows:
* start - Start the resource.
* stop - Stop the resource.
* promote - Promote the resource from a slave resource to a master resource.
* demote - Demote the resource from a master resource to a slave resource.
If no action is specified, the default action is start. For information on master and slave resources, see Section 9.2, “Multistate Resources: Resources That Have Multiple Modes”.
kind option
How to enforce the constraint. The possible values of the kind option are as follows:
* Optional - Only applies if both resources are executing the specified action. For information on optional ordering, see Section 7.2.2, “Advisory Ordering”.
* Mandatory - Always (default value). If the first resource you specified is stopping or cannot be started, the second resource you specified must be stopped. For information on mandatory ordering, see Section 7.2.1, “Mandatory Ordering”.
* Serialize - Ensure that no two stop/start actions occur concurrently for a set of resources.
symmetrical option
If true, which is the default, stop the resources in the reverse order. Default value: true

7.2.1. Mandatory Ordering

A mandatory constraints indicates that the second resource you specify cannot run without the first resource you specify being active. This is the default value of the kind option. Leaving the default value ensures that the second resource you specify will react when the first resource you specify changes state.
  • If the first resource you specified was running and is stopped, the second resource you specified will also be stopped (if it is running).
  • If the first resource you specified resource was not running and cannot be started, the resource you specified will be stopped (if it is running).
  • If the first resource you specified is (re)started while the second resource you specified is running, the second resource you specified will be stopped and restarted.
Note, however, that the cluster reacts to each state change. If the first resource is restarted and is in a started state again before the second resource initiated a stop operation, the second resource will not need to be restarted.

7.2.2. Advisory Ordering

When the kind=Optional option is specified for an order constraint, the constraint is considered optional and only applies if both resources are executing the specified actions. Any change in state by the first resource you specify will have no effect on the second resource you specify.
The following command configures an advisory ordering constraint for the resources named VirtualIP and dummy_resource.
# pcs constraint order VirtualIP then dummy_resource kind=Optional 

7.2.3. Ordered Resource Sets

A common situation is for an administrator to create a chain of ordered resources, where, for example, resource A starts before resource B which starts before resource C. If your configuration requires that you create a set of resources that is colocated and started in order, you can configure a resource group that contains those resources, as described in Section 6.5, “Resource Groups”. There are some situations, however, where configuring the resources that need to start in a specified order as a resource group is not appropriate:
  • You may need to configure resources to start in order and the resources are not necessarily colocated.
  • You may have a resource C that must start after either resource A or B has started but there is no relationship between A and B.
  • You may have resources C and D that must start after both resources A and B have started, but there is no relationship between A and B or between C and D.
In these situations, you can create an order constraint on a set or sets of resources with the pcs constraint order set command.
You can set the following options for a set of resources with the pcs constraint order set command.
  • sequential, which can be set to true or false to indicate whether the set of resources must be ordered relative to each other.
    Setting sequential to false allows a set to be ordered relative to other sets in the ordering constraint, without its members being ordered relative to each other. Therefore, this option makes sense only if multiple sets are listed in the constraint; otherwise, the constraint has no effect.
  • require-all, which can be set to true or false to indicate whether all of the resources in the set must be active before continuing. Setting require-all to false means that only one resource in the set needs to be started before continuing on to the next set. Setting require-all to false has no effect unless used in conjunction with unordered sets, which are sets for which sequential is set to false.
  • action, which can be set to start, promote, demote or stop, as described in Table 7.3, “Properties of an Order Constraint”.
You can set the following constraint options for a set of resources following the setoptions parameter of the pcs constraint order set command.
pcs constraint order set resource1 resource2 [resourceN]... [options] [set resourceX resourceY ... [options]] [setoptions [constraint_options]]
If you have three resources named D1, D2, and D3, the following command configures them as an ordered resource set.
# pcs constraint order set D1 D2 D3

7.2.4. Removing Resources From Ordering Constraints

Use the following command to remove resources from any ordering constraint.
pcs constraint order remove resource1 [resourceN]...

7.3. Colocation of Resources

A colocation constraint determines that the location of one resource depends on the location of another resource.
There is an important side effect of creating a colocation constraint between two resources: it affects the order in which resources are assigned to a node. This is because you cannot place resource A relative to resource B unless you know where resource B is. So when you are creating colocation constraints, it is important to consider whether you should colocate resource A with resource B or resource B with resource A.
Another thing to keep in mind when creating colocation constraints is that, assuming resource A is colocated with resource B, the cluster will also take into account resource A's preferences when deciding which node to choose for resource B.
The following command creates a colocation constraint.
pcs constraint colocation add [master|slave] source_resource with [master|slave] target_resource [score] [options]
For information on master and slave resources, see Section 9.2, “Multistate Resources: Resources That Have Multiple Modes”.
Table 7.4, “Properties of a Colocation Constraint”. summarizes the properties and options for configuring colocation constraints.

Table 7.4. Properties of a Colocation Constraint

FieldDescription
source_resource
The colocation source. If the constraint cannot be satisfied, the cluster may decide not to allow the resource to run at all.
target_resource
The colocation target. The cluster will decide where to put this resource first and then decide where to put the source resource.
score
Positive values indicate the resource should run on the same node. Negative values indicate the resources should not run on the same node. A value of +INFINITY, the default value, indicates that the source_resource must run on the same node as the target_resource. A value of -INFINITY indicates that the source_resource must not run on the same node as the target_resource.

7.3.1. Mandatory Placement

Mandatory placement occurs any time the constraint's score is +INFINITY or -INFINITY. In such cases, if the constraint cannot be satisfied, then the source_resource is not permitted to run. For score=INFINITY, this includes cases where the target_resource is not active.
If you need myresource1 to always run on the same machine as myresource2, you would add the following constraint:
# pcs constraint colocation add myresource1 with myresource2 score=INFINITY
Because INFINITY was used, if myresource2 cannot run on any of the cluster nodes (for whatever reason) then myresource1 will not be allowed to run.
Alternatively, you may want to configure the opposite, a cluster in which myresource1 cannot run on the same machine as myresource2. In this case use score=-INFINITY
# pcs constraint colocation add myresource1 with myresource2 score=-INFINITY
Again, by specifying -INFINITY, the constraint is binding. So if the only place left to run is where myresource2 already is, then myresource1 may not run anywhere.

7.3.2. Advisory Placement

If mandatory placement is about "must" and "must not", then advisory placement is the "I would prefer if" alternative. For constraints with scores greater than -INFINITY and less than INFINITY, the cluster will try to accommodate your wishes but may ignore them if the alternative is to stop some of the cluster resources. Advisory colocation constraints can combine with other elements of the configuration to behave as if they were mandatory.

7.3.3. Colocating Sets of Resources

If your configuration requires that you create a set of resources that is colocated and started in order, you can configure a resource group that contains those resources, as described in Section 6.5, “Resource Groups”. There are some situations, however, where configuring the resources that need to be colocated as a resource group is not appropriate:
  • You may need to colocate a set of resources but the resources do not necessarily need to start in order.
  • You may have a resource C that must be colated with either resource A or B has started but there is no relationship between A and B.
  • You may have resources C and D that must be colocated with both resources A and B, but there is no relationship between A and B or between C and D.
In these situations, you can create a colocation constraint on a set or sets of resources with the pcs constraint colocation set command.
You can set the following options for a set of resources with the pcs constraint colocation set command.
  • sequential, which can be set to true or false to indicate whether the members of the set must be colocated with each other.
    Setting sequential to false allows the members of this set to be colocated with another set listed later in the constraint, regardless of which members of this set are active. Therefore, this option makes sense only if another set is listed after this one in the constraint; otherwise, the constraint has no effect.
  • role, which can be set to Stopped, Started, Master, or Slave. For information on multistate resources, see Section 9.2, “Multistate Resources: Resources That Have Multiple Modes”.
You can set the following constraint options for a set of resources following the setoptions parameter of the pcs constraint colocation set command.
  • kind, to indicate how to enforce the constraint. For information on this option, see Table 7.3, “Properties of an Order Constraint”.
  • symmetrical, to indicate the order in which to stop the resources. If true, which is the default, stop the resources in the reverse order. Default value: true
  • id, to provide a name for the constraint you are defining.
When listing members of a set, each member is colocated with the one before it. For example, "set A B" means "B is colocated with A". However, when listing multiple sets, each set is colocated with the one after it. For example, "set C D sequential=false set A B" means "set C D (where C and D have no relation between each other) is colocated with set A B (where B is colocated with A)".
The following command creates a colocation constraint on a set or sets of resources.
pcs constraint colocation set resource1 resource2 [resourceN]... [options] [set resourceX resourceY ... [options]] [setoptions [constraint_options]]

7.3.4. Removing Colocation Constraints

Use the following command to remove colocation constraints with source_resource.
pcs constraint colocation remove source_resource target_resource

7.4. Displaying Constraints

There are a several commands you can use to display constraints that have been configured.
The following command lists all current location, order, and colocation constraints.
pcs constraint list|show
The following command lists all current location constraints.
  • If resources is specified, location constraints are displayed per resource. This is the default behavior.
  • If nodes is specified, location constraints are displayed per node.
  • If specific resources or nodes are specified, then only information about those resources or nodes is displayed.
pcs constraint location [show resources|nodes [specific nodes|resources]] [--full]
The following command lists all current ordering constraints. If the --full option is specified, show the internal constraint IDs.
pcs constraint order show [--full]
The following command lists all current colocation constraints. If the --full option is specified, show the internal constraint IDs.
pcs constraint colocation show [--full]
The following command lists the constraints that reference specific resources.
pcs constraint ref resource ...

Chapter 8. Managing Cluster Resources

This chapter describes various commands you can use to manage cluster resources. It provides information on the following procedures.

8.1. Manually Moving Resources Around the Cluster

You can override the cluster and force resources to move from their current location. There are two occasions when you would want to do this:
  • When a node is under maintenance, and you need to move all resources running on that node to a different node
  • When individually specified resources needs to be moved
To move all resources running on a node to a different node, you put the node in standby mode. For information on putting a cluster node in standby node, see Section 4.4.5, “Standby Mode”.
You can move individually specified resources in either of the following ways.

8.1.1. Moving a Resource from its Current Node

To move a resource off the node on which it is currently running, use the following command, specifying the resource_id of the node as defined. Specify the destination_node. if you want to indicate on which node to run the resource that you are moving.
pcs resource move resource_id [destination_node] [--master] [lifetime=lifetime]

Note

When you execute the pcs resource move command, this adds a constraint to the resource to prevent it from running on the node on which it is currently running. You can execute the pcs resource clear or the pcs constraint delete command to remove the constraint. This does not necessarily move the resources back to the original node; where the resources can run at that point depends on how you have configured your resources initially.
If you specify the --master parameter of the pcs resource ban command, the scope of the constraint is limited to the master role and you must specify master_id rather than resource_id.
You can optionally configure a lifetime parameter for the pcs resource move command to indicate a period of time the constraint should remain. You specify the units of a lifetime parameter according to the format defined in ISO 8601, which requires that you specify the unit as a capital letter such as Y (for years), M (for months), W (for weeks), D (for days), H (for hours), M (for minutes), and S (for seconds).
To distinguish a unit of minutes(M) from a unit of months(M), you must specify PT before indicating the value in minutes. For example, a lifetime parameter of 5M indicates an interval of five months, while a lifetime parameter of PT5M indicates an interval of five minutes.
The lifetime parameter is checked at intervals defined by the cluster-recheck-interval cluster property. By default this value is 15 minutes. If your configuration requires that you check this parameter more frequently, you can reset this value with the following command.
pcs property set cluster-recheck-interval=value
You can optionally configure a --wait[=n] parameter for the pcs resource ban command to indicate the number of seconds to wait for the resource to start on the destination node before returning 0 if the resource is started or 1 if the resource has not yet started. If you do not specify n, the default resource timeout will be used.
The following command moves the resource resource1 to node example-node2 and prevents it from moving back to the node on which it was originally running for one hour and thirty minutes.
pcs resource move resource1 example-node2 lifetime=PT1H30M
The following command moves the resource resource1 to node example-node2 and prevents it from moving back to the node on which it was originally running for thirty minutes.
pcs resource move resource1 example-node2 lifetime=PT30M
For information on resource constraints, see Chapter 7, Resource Constraints.

8.1.2. Moving a Resource to its Preferred Node

After a resource has moved, either due to a failover or to an administrator manually moving the node, it will not necessarily move back to its original node even after the circumstances that caused the failover have been corrected. To relocate resources to their preferred node, use the following command. A preferred node is determined by the current cluster status, constraints, resource location, and other settings and may change over time.
pcs resource relocate run [resource1] [resource2] ...
If you do not specify any resources, all resource are relocated to their preferred nodes.
This command calculates the preferred node for each resource while ignoring resource stickiness. After calculating the preferred node, it creates location constraints which will cause the resources to move to their preferred nodes. Once the resources have been moved, the constraints are deleted automatically. To remove all constraints created by the pcs resource relocate run command, you can enter the pcs resource relocate clear command. To display the current status of resources and their optimal node ignoring resource stickiness, enter the pcs resource relocate show command.

8.2. Moving Resources Due to Failure

When you create a resource, you can configure the resource so that it will move to a new node after a defined number of failures by setting the migration-threshold option for that resource. Once the threshold has been reached, this node will no longer be allowed to run the failed resource until:
  • The administrator manually resets the resource's failcount using the pcs resource failcount command.
  • The resource's failure-timeout value is reached.
The value of migration-threshold is set to INFINITY by default. INFINITY is defined internally as a very large but finite number. A value of 0 disables the migration-threshold feature.

Note

Setting a migration-threshold for a resource is not the same as configuring a resource for migration, in which the resource moves to another location without loss of state.
The following example adds a migration threshold of 10 to the resource named dummy_resource, which indicates that the resource will move to a new node after 10 failures.
# pcs resource meta dummy_resource migration-threshold=10
You can add a migration threshold to the defaults for the whole cluster with the following command.
# pcs resource defaults migration-threshold=10
To determine the resource's current failure status and limits, use the pcs resource failcount command.
There are two exceptions to the migration threshold concept; they occur when a resource either fails to start or fails to stop. If the cluster property start-failure-is-fatal is set to true (which is the default), start failures cause the failcount to be set to INFINITY and thus always cause the resource to move immediately. For information on the start-failure-is-fatal option, see Table 12.1, “Cluster Properties”.
Stop failures are slightly different and crucial. If a resource fails to stop and STONITH is enabled, then the cluster will fence the node in order to be able to start the resource elsewhere. If STONITH is not enabled, then the cluster has no way to continue and will not try to start the resource elsewhere, but will try to stop it again after the failure timeout.

8.3. Moving Resources Due to Connectivity Changes

Setting up the cluster to move resources when external connectivity is lost is a two step process.
  1. Add a ping resource to the cluster. The ping resource uses the system utility of the same name to test if a list of machines (specified by DNS host name or IPv4/IPv6 address) are reachable and uses the results to maintain a node attribute called pingd.
  2. Configure a location constraint for the resource that will move the resource to a different node when connectivity is lost.
Table 6.1, “Resource Properties” describes the properties you can set for a ping resource.

Table 8.1. Properties of a ping resources

FieldDescription
dampen
The time to wait (dampening) for further changes to occur. This prevents a resource from bouncing around the cluster when cluster nodes notice the loss of connectivity at slightly different times.
multiplier
The number of connected ping nodes gets multiplied by this value to get a score. Useful when there are multiple ping nodes configured.
host_list
The machines to contact in order to determine the current connectivity status. Allowed values include resolvable DNS host names, IPv4 and IPv6 addresses. The entries in the host list are space separated.
The following example command creates a ping resource that verifies connectivity to gateway.example.com. In practice, you would verify connectivity to your network gateway/router. You configure the ping resource as a clone so that the resource will run on all cluster nodes.
# pcs resource create ping ocf:pacemaker:ping dampen=5s multiplier=1000 host_list=gateway.example.com clone
The following example configures a location constraint rule for the existing resource named Webserver. This will cause the Webserver resource to move to a host that is able to ping www.example.com if the host that it is currently running on cannot ping www.example.com
# pcs constraint location Webserver rule score=-INFINITY pingd lt 1 or not_defined pingd

8.4. Enabling, Disabling, and Banning Cluster Resources

In addition to the pcs resource move and pcs resource relocate commands described in Section 8.1, “Manually Moving Resources Around the Cluster”, there are a variety of other commands you can use to control the behavior of cluster resources.
You can manually stop a running resource and prevent the cluster from starting it again with the following command. Depending on the rest of the configuration (constraints, options, failures, and so on), the resource may remain started. If you specify the --wait option, pcs will wait up to 'n' seconds for the resource to stop and then return 0 if the resource is stopped or 1 if the resource has not stopped. If 'n' is not specified it defaults to 60 minutes.
pcs resource disable resource_id [--wait[=n]]
You can use the following command to allow the cluster to start a resource. Depending on the rest of the configuration, the resource may remain stopped. If you specify the --wait option, pcs will wait up to 'n' seconds for the resource to start and then return 0 if the resource is started or 1 if the resource has not started. If 'n' is not specified it defaults to 60 minutes.
pcs resource enable resource_id [--wait[=n]]
Use the following command to prevent a resource from running on a specified node, or on the current node if no node is specified.
pcs resource ban resource_id [node] [--master] [lifetime=lifetime] [--wait[=n]]
Note that when you execute the pcs resource ban command, this adds a -INFINITY location constraint to the resource to prevent it from running on the indicated node. You can execute the pcs resource clear or the pcs constraint delete command to remove the constraint. This does not necessarily move the resources back to the indicated node; where the resources can run at that point depends on how you have configured your resources initially. For information on resource constraints, see Chapter 7, Resource Constraints.
If you specify the --master parameter of the pcs resource ban command, the scope of the constraint is limited to the master role and you must specify master_id rather than resource_id.
You can optionally configure a lifetime parameter for the pcs resource ban command to indicate a period of time the constraint should remain. For information on specifying units for the lifetime parameter and on specifying the intervals at which the lifetime parameter should be checked, see Section 8.1, “Manually Moving Resources Around the Cluster”.
You can optionally configure a --wait[=n] parameter for the pcs resource ban command to indicate the number of seconds to wait for the resource to start on the destination node before returning 0 if the resource is started or 1 if the resource has not yet started. If you do not specify n, the default resource timeout will be used.
You can use the debug-start parameter of the pcs resource command to force a specified resource to start on the current node, ignoring the cluster recommendations and printing the output from starting the resource. This is mainly used for debugging resources; starting resources on a cluster is (almost) always done by Pacemaker and not directly with a pcs command. If your resource is not starting, it is usually due to either a misconfiguration of the resource (which you debug in the system log), constraints that the resource from starting, or the resource being disabled. You can use this command to test resource configuration, but it should not normally be used to start resources in a cluster.
The format of the debug-start command is as follows.
pcs resource debug-start resource_id

8.5. Disabling a Monitor Operations

The easiest way to stop a recurring monitor is to delete it. However, there can be times when you only want to disable it temporarily. In such cases, add enabled="false" to the operation’s definition. When you want to reinstate the monitoring operation, set enabled="true" to the operation's definition.

8.6. Managed Resources

You can set a resource to unmanaged mode, which indicates that the resource is still in the configuration but Pacemaker does not manage the resource.
The following command sets the indicated resources to unmanaged mode.
pcs resource unmanage resource1  [resource2] ...
The following command sets resources to managed mode, which is the default state.
pcs resource manage resource1  [resource2] ...
You can specify the name of a resource group with the pcs resource manage or pcs resource unmanage command. The command will act on all of the resources in the group, so that you can set all of the resources in a group to managed or unmanaged mode with a single command and then manage the contained resources individually.

Chapter 9. Advanced Configuration

This chapter describes advanced resource types and advanced configuration features that Pacemaker supports.

9.1. Resource Clones

You can clone a resource so that the resource can be active on multiple nodes. For example, you can use cloned resources to configure multiple instances of an IP resource to distribute throughout a cluster for node balancing. You can clone any resource provided the resource agent supports it. A clone consists of one resource or one resource group.

Note

Only resources that can be active on multiple nodes at the same time are suitable for cloning. For example, a Filesystem resource mounting a non-clustered file system such as ext4 from a shared memory device should not be cloned. Since the ext4 partition is not cluster aware, this file system is not suitable for read/write operations occurring from multiple nodes at the same time.

9.1.1. Creating and Removing a Cloned Resource

You can create a resource and a clone of that resource at the same time with the following command.
pcs resource create resource_id standard:provider:type|type [resource options]  \
clone  [meta clone_options]
The name of the clone will be resource_id-clone.
You cannot create a resource group and a clone of that resource group in a single command.
Alternately, you can create a clone of a previously-created resource or resource group with the following command.
pcs resource clone resource_id | group_name [clone_options]...
The name of the clone will be resource_id-clone or group_name-clone.

Note

You need to configure resource configuration changes on one node only.

Note

When configuring constraints, always use the name of the group or clone.
When you create a clone of a resource, the clone takes on the name of the resource with -clone appended to the name. The following commands creates a resource of type apache named webfarm and a clone of that resource named webfarm-clone.
# pcs resource create webfarm apache clone
Use the following command to remove a clone of a resource or a resource group. This does not remove the resource or resource group itself.
pcs resource unclone resource_id | group_name
For information on resource options, see Section 6.1, “Resource Creation”.
Table 9.1, “Resource Clone Options” describes the options you can specify for a cloned resource.

Table 9.1. Resource Clone Options

FieldDescription
priority, target-role, is-managed
Options inherited from resource that is being cloned, as described in Table 6.3, “Resource Meta Options”.
clone-max
How many copies of the resource to start. Defaults to the number of nodes in the cluster.
clone-node-max
How many copies of the resource can be started on a single node; the default value is 1.
notify
When stopping or starting a copy of the clone, tell all the other copies beforehand and when the action was successful. Allowed values: false, true. The default value is false.
globally-unique
Does each copy of the clone perform a different function? Allowed values: false, true
If the value of this option is false, these resources behave identically everywhere they are running and thus there can be only one copy of the clone active per machine.
If the value of this option is true, a copy of the clone running on one machine is not equivalent to another instance, whether that instance is running on another node or on the same node. The default value is true if the value of clone-node-max is greater than one; otherwise the default value is false.
ordered
Should the copies be started in series (instead of in parallel). Allowed values: false, true. The default value is false.
interleave
Changes the behavior of ordering constraints (between clones/masters) so that copies of the first clone can start or stop as soon as the copy on the same node of the second clone has started or stopped (rather than waiting until every instance of the second clone has started or stopped). Allowed values: false, true. The default value is false.

9.1.2. Clone Constraints

In most cases, a clone will have a single copy on each active cluster node. You can, however, set clone-max for the resource clone to a value that is less than the total number of nodes in the cluster. If this is the case, you can indicate which nodes the cluster should preferentially assign copies to with resource location constraints. These constraints are written no differently to those for regular resources except that the clone's id must be used.
The following command creates a location constraint for the cluster to preferentially assign resource clone webfarm-clone to node1.
# pcs constraint location webfarm-clone prefers node1
Ordering constraints behave slightly differently for clones. In the example below, webfarm-stats will wait until all copies of webfarm-clone that need to be started have done so before being started itself. Only if no copies of webfarm-clone can be started then webfarm-stats will be prevented from being active. Additionally, webfarm-clone will wait for webfarm-stats to be stopped before stopping itself.
# pcs constraint order start webfarm-clone then webfarm-stats
Colocation of a regular (or group) resource with a clone means that the resource can run on any machine with an active copy of the clone. The cluster will choose a copy based on where the clone is running and the resource's own location preferences.
Colocation between clones is also possible. In such cases, the set of allowed locations for the clone is limited to nodes on which the clone is (or will be) active. Allocation is then performed as normally.
The following command creates a colocation constraint to ensure that the resource webfarm-stats runs on the same node as an active copy of webfarm-clone.
# pcs constraint colocation add webfarm-stats with webfarm-clone

9.1.3. Clone Stickiness

To achieve a stable allocation pattern, clones are slightly sticky by default. If no value for resource-stickiness is provided, the clone will use a value of 1. Being a small value, it causes minimal disturbance to the score calculations of other resources but is enough to prevent Pacemaker from needlessly moving copies around the cluster.

9.2. Multistate Resources: Resources That Have Multiple Modes

Multistate resources are a specialization of Clone resources. They allow the instances to be in one of two operating modes; these are called Master and Slave. The names of the modes do not have specific meanings, except for the limitation that when an instance is started, it must come up in the Slave state.
You can create a resource as a master/slave clone with the following single command.
pcs resource create resource_id standard:provider:type|type [resource options] master [master_options]
The name of the master/slave clone will be resource_id-master.

Note

For Red Hat Enterprise Linux release 7.3 and earlier, use the following format to create a master/slave clone.
pcs resource create resource_id standard:provider:type|type [resource options] --master [meta master_options]
Alternately, you can create a master/slave resource from a previously-created resource or resource group with the following command: When you use this command, you can specify a name for the master/slave clone. If you do not specify a name, the name of the master/slave clone will be resource_id-master or group_name-master.
pcs resource master master/slave_name resource_id|group_name [master_options]
For information on resource options, see Section 6.1, “Resource Creation”.
Table 9.2, “Properties of a Multistate Resource” describes the options you can specify for a multistate resource.

Table 9.2. Properties of a Multistate Resource

FieldDescription
id
Your name for the multistate resource
priority, target-role, is-managed
clone-max, clone-node-max, notify, globally-unique, ordered, interleave
master-max
How many copies of the resource can be promoted to master status; default 1.
master-node-max
How many copies of the resource can be promoted to master status on a single node; default 1.

9.2.1. Monitoring Multi-State Resources

To add a monitoring operation for the master resource only, you can add an additional monitor operation to the resource. Note, however, that every monitor operation on a resource must have a different interval.
The following example configures a monitor operation with an interval of 11 seconds on the master resource for ms_resource. This monitor operation is in addition to the default monitor operation with the default monitor interval of 10 seconds.
# pcs resource op add ms_resource interval=11s role=Master

9.2.2. Multistate Constraints

In most cases, a multistate resources will have a single copy on each active cluster node. If this is not the case, you can indicate which nodes the cluster should preferentially assign copies to with resource location constraints. These constraints are written no differently than those for regular resources.
For information on resource location constraints, see Section 7.1, “Location Constraints”.
You can create a colocation constraint which specifies whether the resources are master or slave resources. The following command creates a resource colocation constraint.
pcs constraint colocation add [master|slave] source_resource with [master|slave] target_resource [score] [options]
For information on colocation constraints, see Section 7.3, “Colocation of Resources”.
When configuring an ordering constraint that includes multistate resources, one of the actions that you can specify for the resources is promote, indicating that the resource be promoted from slave to master. Additionally, you can specify an action of demote, indicated that the resource be demoted from master to slave.
The command for configuring an order constraint is as follows.
pcs constraint order [action] resource_id then [action] resource_id [options]
For information on resource order constraints, see Section 7.2, “Order Constraints”.

9.2.3. Multistate Stickiness

To achieve a stable allocation pattern, multistate resources are slightly sticky by default. If no value for resource-stickiness is provided, the multistate resource will use a value of 1. Being a small value, it causes minimal disturbance to the score calculations of other resources but is enough to prevent Pacemaker from needlessly moving copies around the cluster.

9.3. Configuring a Virtual Domain as a Resource

You can configure a virtual domain that is managed by the libvirt virtualization framework as a cluster resource with the pcs resource create command, specifying VirtualDomain as the resource type.
When configuring a virtual domain as a resource, take the following considerations into account:
  • A virtual domain should be stopped before you configure it as a cluster resource.
  • Once a virtual domain is a cluster resource, it should not be started, stopped, or migrated except through the cluster tools.
  • Do not configure a virtual domain that you have configured as a cluster resource to start when its host boots.
  • All nodes must have access to the necessary configuration files and storage devices for each managed virtual domain.
If you want the cluster to manage services within the virtual domain itself, you can configure the virtual domain as a guest node. For information on configuring guest nodes, see Section 9.4, “The pacemaker_remote Service”
For information on configuring virtual domains, see the Virtualization Deployment and Administration Guide.
Table 9.3, “Resource Options for Virtual Domain Resources” describes the resource options you can configure for a VirtualDomain resource.

Table 9.3. Resource Options for Virtual Domain Resources

FieldDefaultDescription
config
(required) Absolute path to the libvirt configuration file for this virtual domain.
hypervisor
System dependent
Hypervisor URI to connect to. You can determine the system's default URI by running the virsh --quiet uri command.
force_stop
0
Always forcefully shut down ("destroy") the domain on stop. The default behavior is to resort to a forceful shutdown only after a graceful shutdown attempt has failed. You should set this to true only if your virtual domain (or your virtualization back end) does not support graceful shutdown.
migration_transport
System dependent
Transport used to connect to the remote hypervisor while migrating. If this parameter is omitted, the resource will use libvirt's default transport to connect to the remote hypervisor.
migration_network_suffix
Use a dedicated migration network. The migration URI is composed by adding this parameter's value to the end of the node name. If the node name is a fully qualified domain name (FQDN), insert the suffix immediately prior to the first period (.) in the FQDN. Ensure that this composed host name is locally resolvable and the associated IP address is reachable through the favored network.
monitor_scripts
To additionally monitor services within the virtual domain, add this parameter with a list of scripts to monitor. Note: When monitor scripts are used, the start and migrate_from operations will complete only when all monitor scripts have completed successfully. Be sure to set the timeout of these operations to accommodate this delay
autoset_utilization_cpu
true
If set to true, the agent will detect the number of domainU's vCPUs from virsh, and put it into the CPU utilization of the resource when the monitor is executed.
autoset_utilization_hv_memory
true
If set it true, the agent will detect the number of Max memory from virsh, and put it into the hv_memory utilization of the source when the monitor is executed.
migrateport
random highport
This port will be used in the qemu migrate URI. If unset, the port will be a random highport.
snapshot
Path to the snapshot directory where the virtual machine image will be stored. When this parameter is set, the virtual machine's RAM state will be saved to a file in the snapshot directory when stopped. If on start a state file is present for the domain, the domain will be restored to the same state it was in right before it stopped last. This option is incompatible with the force_stop option.
In addition to the VirtualDomain resource options, you can configure the allow-migrate metadata option to allow live migration of the resource to another node. When this option is set to true, the resource can be migrated without loss of state. When this option is set to false, which is the default state, the virtual domain will be shut down on the first node and then restarted on the second node when it is moved from one node to the other.
Use the following procedure to create a VirtualDomain resource:
  1. To create the VirtualDomain resource agent for the management of the virtual machine, Pacemaker requires the virtual machine's xml config file to be dumped to a file on disk. For example, if you created a virtual machine named guest1, dump the xml to a file somewhere on the host. You can use a file name of your choosing; this example uses /etc/pacemaker/guest1.xml.
    # virsh dumpxml guest1 > /etc/pacemaker/guest1.xml
  2. If it is running, shut down the guest node. Pacemaker will start the node when it is configured in the cluster.
  3. Configure the VirtualDoman resource with the pcs resource create command. For example, The following command configures a VirtualDomain resource named VM. Since the allow-migrate option is set to true a pcs move VM nodeX command would be done as a live migration.
    # pcs resource create VM VirtualDomain config=.../vm.xml \
           migration_transport=ssh meta allow-migrate=true
    

9.4. The pacemaker_remote Service

The pacemaker_remote service allows nodes not running corosync to integrate into the cluster and have the cluster manage their resources just as if they were real cluster nodes.
Among the capabilities that the pacemaker_remote service provides are the following:
  • The pacemaker_remote service allows you to scale beyond the corosync 16-node limit.
  • The pacemaker_remote service allows you to manage a virtual environment as a cluster resource and also to manage individual services within the virtual environment as cluster resources.
The following terms are used to describe the pacemaker_remote service.
  • cluster node — A node running the High Availability services (pacemaker and corosync).
  • remote node — A node running pacemaker_remote to remotely integrate into the cluster without requiring corosync cluster membership. A remote node is configured as a cluster resource that uses the ocf:pacemaker:remote resource agent.
  • guest node — A virtual guest node running the pacemaker_remote service. The virtual guest resource is managed by the cluster; it is both started by the cluster and integrated into the cluster as a remote node.
  • pacemaker_remote — A service daemon capable of performing remote application management within remote nodes and guest nodes (KVM and LXC) in a Pacemaker cluster environment. This service is an enhanced version of Pacemaker’s local resource management daemon (LRMD) that is capable of managing resources remotely on a node not running corosync.
  • LXC — A Linux Container defined by the libvirt-lxc Linux container driver.
A Pacemaker cluster running the pacemaker_remote service has the following characteristics.
  • Remote nodes and guest nodes run the pacemaker_remote service (with very little configuration required on the virtual machine side).
  • The cluster stack (pacemaker and corosync), running on the cluster nodes, connects to the pacemaker_remote service on the remote nodes, allowing them to integrate into the cluster.
  • The cluster stack (pacemaker and corosync), running on the cluster nodes, launches the guest nodes and immediately connects to the pacemaker_remote service on the guest nodes, allowing them to integrate into the cluster.
The key difference between the cluster nodes and the remote and guest nodes that the cluster nodes manage is that the remote and guest nodes are not running the cluster stack. This means the remote and guest nodes have the following limitations:
  • they do not take place in quorum
  • they do not execute fencing device actions
  • they are not eligible to be the cluster's Designated Controller (DC)
  • they do not themselves run the full range of pcs commands
On the other hand, remote nodes and guest nodes are not bound to the scalability limits associated with the cluster stack.
Other than these noted limitations, the remote and guest nodes behave just like cluster nodes in respect to resource management, and the remote and guest nodes can themselves be fenced. The cluster is fully capable of managing and monitoring resources on each remote and guest node: You can build constraints against them, put them in standby, or perform any other action you perform on cluster nodes with the pcs commands. Remote and guest nodes appear in cluster status output just as cluster nodes do.

9.4.1. Host and Guest Authentication

The connection between cluster nodes and pacemaker_remote is secured using Transport Layer Security (TLS) with pre-shared key (PSK) encryption and authentication over TCP (using port 3121 by default). This means both the cluster node and the node running pacemaker_remote must share the same private key. By default this key must be placed at /etc/pacemaker/authkey on both cluster nodes and remote nodes.
As of Red Hat Enterprise Linux 7.4, the pcs cluster node add-guest command sets up the authkey for guest nodes and the pcs cluster node add-remote command sets up the authkey for remote nodes.

9.4.2. Guest Node Resource Options

When configuring a virtual machine or LXC resource to act as a guest node, you create a VirtualDomain resource, which manages the virtual machine. For descriptions of the options you can set for a VirtualDomain resource, see Table 9.3, “Resource Options for Virtual Domain Resources”.
In addition to the VirtualDomain resource options, metadata options define the resource as a guest node and define the connection parameters. As of Red Hat Enterprise Linux 7.4, you should set these resource options with the pcs cluster node add-guest command. In releases earlier than 7.4, you can set these options when creating the resource. Table 9.4, “Metadata Options for Configuring KVM/LXC Resources as Remote Nodes” describes these metadata options.

Table 9.4. Metadata Options for Configuring KVM/LXC Resources as Remote Nodes

FieldDefaultDescription
remote-node
<none>
The name of the guest node this resource defines. This both enables the resource as a guest node and defines the unique name used to identify the guest node. WARNING: This value cannot overlap with any resource or node IDs.
remote-port
3121
Configures a custom port to use for the guest connection to pacemaker_remote
remote-addr
remote-node value used as host name
The IP address or host name to connect to if remote node’s name is not the host name of the guest
remote-connect-timeout
60s
Amount of time before a pending guest connection will time out

9.4.3. Remote Node Resource Options

A remote node is defined as a cluster resource with ocf:pacemaker:remote as the resource agent. In Red Hat Enterprise Linux 7.4, you should create this resource with the pcs cluster node add-remote command. In releases earlier than 7.4, you can create this resource with the pcs resource create command. Table 9.5, “Resource Options for Remote Nodes” describes the resource options you can configure for a remote resource.

Table 9.5. Resource Options for Remote Nodes

FieldDefaultDescription
reconnect_interval
0
Time in seconds to wait before attempting to reconnect to a remote node after an active connection to the remote node has been severed. This wait is recurring. If reconnect fails after the wait period, a new reconnect attempt will be made after observing the wait time. When this option is in use, Pacemaker will keep attempting to reach out and connect to the remote node indefinitely after each wait interval.
server
Server location to connect to. This can be an IP address or host name.
port
TCP port to connect to.

9.4.4. Changing Default Port Location

If you need to change the default port location for either Pacemaker or pacemaker_remote, you can set the PCMK_remote_port environment variable that affects both of these daemons. This environment variable can be enabled by placing it in the /etc/sysconfig/pacemaker file as follows.
#==#==# Pacemaker Remote
...
#
# Specify a custom port for Pacemaker Remote connections
PCMK_remote_port=3121
When changing the default port used by a particular guest node or remote node, the PCMK_remote_port variable must be set in that node's /etc/sysconfig/pacemaker file, and the cluster resource creating the guest node or remote node connection must also be configured with the same port number (using the remote-port metadata option for guest nodes, or the port option for remote nodes).

9.4.5. Configuration Overview: KVM Guest Node

This section provides a high-level summary overview of the steps to perform to have Pacemaker launch a virtual machine and to integrate that machine as a guest node, using libvirt and KVM virtual guests.
  1. Configure the VirtualDomain resources, as described in Section 9.3, “Configuring a Virtual Domain as a Resource”.
  2. On systems running Red Hat Enterprise Linux 7.3 and earlier, put the same encryption key with the path /etc/pacemaker/authkey on every cluster node and virtual machine with the following procedure. This secures remote communication and authentication.
    1. Enter the following set of commands on every node to create the authkey directory with secure permissions.
      # mkdir -p --mode=0750 /etc/pacemaker
      # chgrp haclient /etc/pacemaker
    2. The following command shows one method to create an encryption key. You should create the key only once and then copy it to all of the nodes.
      # dd if=/dev/urandom of=/etc/pacemaker/authkey bs=4096 count=1
  3. For Red Hat Enterprise Linux 7.4, enter the following commands on every virtual machine to install pacemaker_remote packages, start the pcsd service and enable it to run on startup, and allow TCP port 3121 through the firewall.
    # yum install pacemaker-remote resource-agents pcs
    # systemctl start pcsd.service
    # systemctl enable pcsd.service
    # firewall-cmd --add-port 3121/tcp --permanent
    # firewall-cmd --add-port 2224/tcp --permanent
    # firewall-cmd --reload
    For Red Hat Enterprise Linux 7.3 and earlier, run the following commands on every virtual machine to install pacemaker_remote packages, start the pacemaker_remote service and enable it to run on startup, and allow TCP port 3121 through the firewall.
    # yum install pacemaker-remote resource-agents pcs
    # systemctl start pacemaker_remote.service
    # systemctl enable pacemaker_remote.service
    # firewall-cmd --add-port 3121/tcp --permanent
    # firewall-cmd --add-port 2224/tcp --permanent
    # firewall-cmd --reload
  4. Give each virtual machine a static network address and unique host name, which should be known to all nodes. For information on setting a static IP address for the guest virtual machine, see the Virtualization Deployment and Administration Guide.
  5. For Red Hat Enterprise Linux 7.4 and later, use the following command to convert an existing VirtualDomain resource into a guest node. This command must be run on a cluster node and not on the guest node which is being added. In addition to converting the resource, this command copies the /etc/pacemaker/authkey to the guest node and starts and enables the pacemaker_remote daemon on the guest node.
    pcs cluster node add-guest hostname resource_id [options]
    
    For Red Hat Enterprise Linux 7.3 and earlier, use the following command to convert an existing VirtualDomain resource into a guest node. This command must be run on a cluster node and not on the guest node which is being added.
    pcs cluster remote-node add hostname resource_id [options]
    
  6. After creating the VirtualDomain resource, you can treat the guest node just as you would treat any other node in the cluster. For example, you can create a resource and place a resource constraint on the resource to run on the guest node as in the following commands, which are run from a cluster node. As of Red Hat Enterprise Linux 7.3, you can include guest nodes in groups, which allows you to group a storage device, file system, and VM.
    # pcs resource create webserver apache configfile=/etc/httpd/conf/httpd.conf op monitor interval=30s
    # pcs constraint location webserver prefers guest1

9.4.6. Configuration Overview: Remote Node (Red Hat Enterprise Linux 7.4)

This section provides a high-level summary overview of the steps to perform to configure a Pacemaker Remote node and to integrate that node into an existing Pacemaker cluster environment for Red Hat Enterprise Linux 7.4.
  1. On the node that you will be configuring as a remote node, allow cluster-related services through the local firewall.
    # firewall-cmd --permanent --add-service=high-availability
    success
    # firewall-cmd --reload
    success
    

    Note

    If you are using iptables directly, or some other firewall solution besides firewalld, simply open the following ports: TCP ports 2224 and 3121.
  2. Install the pacemaker_remote daemon on the remote node.
    # yum install -y pacemaker-remote resource-agents pcs
  3. Start and enable pcsd on the remote node.
    # systemctl start pcsd.service
    # systemctl enable pcsd.service
  4. Add the remote node resource to the cluster with the following command. This command also syncs all relevant configuration files to the new node, starts the node, and configures it to start pacemaker_remote on boot. This command must be run on a cluster node and not on the guest node which is being added.
    # pcs cluster node add-remote remote1
  5. After adding the remote resource to the cluster, you can treat the remote node just as you would treat any other node in the cluster. For example, you can create a resource and place a resource constraint on the resource to run on the remote node as in the following commands, which are run from a cluster node.
    # pcs resource create webserver apache configfile=/etc/httpd/conf/httpd.conf op monitor interval=30s
    # pcs constraint location webserver prefers remote1

    Warning

    Never involve a remote node connection resource in a resource group, colocation constraint, or order constraint.
  6. Configure fencing resources for the remote node. Remote nodes are fenced the same way as cluster nodes. Configure fencing resources for use with remote nodes the same as you would with cluster nodes. Note, however, that remote nodes can never initiate a fencing action. Only cluster nodes are capable of actually executing a fencing operation against another node.

9.4.7. Configuration Overview: Remote Node (Red Hat Enterprise Linux 7.3 and earlier)

This section provides a high-level summary overview of the steps to perform to configure a Pacemaker Remote node and to integrate that node into an existing Pacemaker cluster environment in a Red Hat Enterprise Linux 7.3 (and earlier) system.
  1. On the node that you will be configuring as a remote node, allow cluster-related services through the local firewall.
    # firewall-cmd --permanent --add-service=high-availability
    success
    # firewall-cmd --reload
    success
    

    Note

    If you are using iptables directly, or some other firewall solution besides firewalld, simply open the following ports: TCP ports 2224 and 3121.
  2. Install the pacemaker_remote daemon on the remote node.
    # yum install -y pacemaker-remote resource-agents pcs
  3. All nodes (both cluster nodes and remote nodes) must have the same authentication key installed for the communication to work correctly. If you already have a key on an existing node, use that key and copy it to the remote node. Otherwise, create a new key on the remote node.
    Enter the following set of commands on the remote node to create a directory for the authentication key with secure permissions.
    # mkdir -p --mode=0750 /etc/pacemaker
    # chgrp haclient /etc/pacemaker
    The following command shows one method to create an encryption key on the remote node.
    # dd if=/dev/urandom of=/etc/pacemaker/authkey bs=4096 count=1
  4. Start and enable the pacemaker_remote daemon on the remote node.
    # systemctl enable pacemaker_remote.service
    # systemctl start pacemaker_remote.service
  5. On the cluster node, create a location for the shared authentication key with the same path as the authentication key on the remote node and copy the key into that directory. In this example, the key is copied from the remote node where the key was created.
    # mkdir -p --mode=0750 /etc/pacemaker
    # chgrp haclient /etc/pacemaker
    # scp remote1:/etc/pacemaker/authkey /etc/pacemaker/authkey
  6. Enter the following command from a cluster node to create a remote resource. In this case the remote node is remote1.
    # pcs resource create remote1 ocf:pacemaker:remote
  7. After creating the remote resource, you can treat the remote node just as you would treat any other node in the cluster. For example, you can create a resource and place a resource constraint on the resource to run on the remote node as in the following commands, which are run from a cluster node.
    # pcs resource create webserver apache configfile=/etc/httpd/conf/httpd.conf op monitor interval=30s
    # pcs constraint location webserver prefers remote1

    Warning

    Never involve a remote node connection resource in a resource group, colocation constraint, or order constraint.
  8. Configure fencing resources for the remote node. Remote nodes are fenced the same way as cluster nodes. Configure fencing resources for use with remote nodes the same as you would with cluster nodes. Note, however, that remote nodes can never initiate a fencing action. Only cluster nodes are capable of actually executing a fencing operation against another node.

9.4.8. System Upgrades and pacemaker_remote

As of Red Hat Enterprise Linux 7.3, if the pacemaker_remote service is stopped on an active Pacemaker Remote node, the cluster will gracefully migrate resources off the node before stopping the node. This allows you to perform software upgrades and other routine maintenance procedures without removing the node from the cluster. Once pacemaker_remote is shut down, however, the cluster will immediately try to reconnect. If pacemaker_remote is not restarted within the resource's monitor timeout, the cluster will consider the monitor operation as failed.
If you wish to avoid monitor failures when the pacemaker_remote service is stopped on an active Pacemaker Remote node, you can use the following procedure to take the node out of the cluster before performing any system administration that might stop pacemaker_remote

Warning

For Red Hat Enterprise Linux release 7.2 and earlier, if pacemaker_remote stops on a node that is currently integrated into a cluster, the cluster will fence that node. If the stop happens automatically as part of a yum update process, the system could be left in an unusable state (particularly if the kernel is also being upgraded at the same time as pacemaker_remote). For Red Hat Enterprise Linux release 7.2 and earlier you must use the following procedure to take the node out of the cluster before performing any system administration that might stop pacemaker_remote.
  1. Stop the node's connection resource with the pcs resource disable resourcename, which will move all services off the node. For guest nodes, this will also stop the VM, so the VM must be started outside the cluster (for example, using virsh) to perform any maintenance.
  2. Perform the required maintenance.
  3. When ready to return the node to the cluster, re-enable the resource with the pcs resource enable.

9.5. Pacemaker Support for Docker Containers (Technology Preview)

Important

Pacemaker support for Docker containers is provided for technology preview only. For details on what "technology preview" means, see Technology Preview Features Support Scope.
There is one exception to this feature being Technology Preview: As of Red Hat Enterprise Linux 7.4, Red Hat fully supports the usage of Pacemaker bundles for Red Hat Openstack Platform (RHOSP) deployments.
Pacemaker supports a special syntax for launching a Docker container with any infrastructure it requires: the bundle. After you have created a Pacemaker bundle, you can create a Pacemaker resource that the bundle encapsulates.

9.5.1. Configuring a Pacemaker Bundle Resource

The syntax for the command to create a Pacemaker bundle for a Docker container is as follows. This command creates a bundle that encapsulates no other resources. For information on creating a cluster resource in a bundle see Section 9.5.2, “Configuring a Pacemaker Resource in a Bundle”.
pcs resource bundle create bundle_id container docker [container_options] [network network_options] [port-map port_options]...  [storage-map storage_options]... [meta meta_options] [--disabled] [--wait[=n]]
The required bundle_id parameter must be a unique name for the bundle. If the --disabled option is specified, the bundle is not started automatically. If the --wait option is specified, Pacemaker will wait up to n seconds for the bundle to start and then return 0 on success or 1 on error. If n is not specified it defaults to 60 minutes.
The following sections describe the parameters you can configure for each element of a Pacemaker bundle.

9.5.1.1. Docker Parameters

Table 9.6, “Docker Container Parameters” describes the docker container options you can set for a bundle.

Note

Before configuring a docker bundle in Pacemaker, you must install Docker and supply a fully configured Docker image on every node allowed to run the bundle.

Table 9.6. Docker Container Parameters

FieldDefaultDescription
image
Docker image tag (required)
replicas
Value of promoted-max if that is positive, otherwise 1.
A positive integer specifying the number of container instances to launch
replicas-per-host
1
A positive integer specifying the number of container instances allowed to run on a single node
promoted-max
0
A non-negative integer that, if positive, indicates that the containerized service should be treated as a multistate service, with this many replicas allowed to run the service in the master role
network
If specified, this will be passed to the docker run command as the network setting for the Docker container.
run-command
/usr/sbin/pacemaker_remoted if the bundle contains a resource, otherwise none
This command will be run inside the container when launching it ("PID 1"). If the bundle contains a resource, this command must start the pacemaker_remoted daemon (but it could, for example, be a script that performs others tasks as well).
options
Extra command-line options to pass to the docker run command

9.5.1.2. Bundle Network Parameters

Table 9.7, “Bundle Resource Network Parameters” describes the network options you can set for a bundle.

Table 9.7. Bundle Resource Network Parameters

FieldDefaultDescription
add-host
TRUE
If TRUE, and ip-range-start is used, Pacemaker will automatically ensure that the /etc/hosts file inside the containers has entries for each replica name and its assigned IP.
ip-range-start
If specified, Pacemaker will create an implicit ocf:heartbeat:IPaddr2 resource for each container instance, starting with this IP address, using as many sequential addresses as were specified as the replicas parameter for the Docker element. These addresses can be used from the host’s network to reach the service inside the container, although it is not visible within the container itself. Only IPv4 addresses are currently supported.
host-netmask
32
If ip-range-start is specified, the IP addresses are created with this CIDR netmask (as a number of bits).
host-interface
If ip-range-start is specified, the IP addresses are created on this host interface (by default, it will be determined from the IP address).
control-port
3121
If the bundle contains a Pacemaker resource, the cluster will use this integer TCP port for communication with Pacemaker Remote inside the container. Changing this is useful when the container is unable to listen on the default port, which could happen when the container uses the host’s network rather than ip-range-start (in which case replicas-per-host must be 1), or when the bundle may run on a Pacemaker Remote node that is already listening on the default port. Any PCMK_remote_port environment variable set on the host or in the container is ignored for bundle connections.

Note

Replicas are named by the bundle ID plus a dash and an integer counter starting with zero. For example, if a bundle named httpd-bundle has configured replicas=2, its containers will be named httpd-bundle-0 and httpd-bundle-1.
In addition to the network parameters, you can optionally specify port-map parameters for a bundle. Table 9.8, “Bundle Resource port-map Parameters” describes these port-map parameters.

Table 9.8. Bundle Resource port-map Parameters

FieldDefaultDescription
id
A unique name for the port mapping (required)
port
If this is specified, connections to this TCP port number on the host network (on the container’s assigned IP address, if ip-range-start is specified) will be forwarded to the container network. Exactly one of port or range must be specified in a port-mapping.
internal-port
Value of port
If port and internal-port are specified, connections to port on the host’s network will be forwarded to this port on the container network.
range
If range is specified, connections to these TCP port numbers (expressed as first_port-last_port) on the host network (on the container’s assigned IP address, if ip-range-start is specified) will be forwarded to the same ports in the container network. Exactly one of port or range must be specified in a port mapping.

Note

If the bundle contains a resource, Pacemaker will automatically map the control-port, so it is not necessary to specify that port in a port mapping.

9.5.1.3. Bundle Storage Parameters

You can optionally configure storage-map parameters for a bundle. Table 9.9, “Bundle Resource Storage Mapping Parameters” describes these parameters.

Table 9.9. Bundle Resource Storage Mapping Parameters

FieldDefaultDescription
id
A unique name for the storage mapping (required)
source-dir
The absolute path on the host’s filesystem that will be mapped into the container. Exactly one of source-dir and source-dir-root parameter must be specified when configuring a storage-map parameter.
source-dir-root
The start of a path on the host’s filesystem that will be mapped into the container, using a different subdirectory on the host for each container instance. The subdirectory will be named with the same name as the bundle name, plus a dash and an integer counter starting with 0. Exactly one source-dir and source-dir-root parameter must be specified when configuring a storage-map parameter.
target-dir
The path name within the container where the host storage will be mapped (required)
options
File system mount options to use when mapping the storage
As an example of how subdirectories on a host are named using the source-dir-root parameter, if source-dir-root=/path/to/my/directory, target-dir=/srv/appdata, and the bundle is named mybundle with replicas=2, then the cluster will create two container instances with host names mybundle-0 and mybundle-1 and create two directories on the host running the containers: /path/to/my/directory/mybundle-0 and /path/to/my/directory/mybundle-1. Each container will be given one of those directories, and any application running inside the container will see the directory as /srv/appdata.

Note

Pacemaker does not define the behavior if the source directory does not already exist on the host. However, it is expected that the container technology or its resource agent will create the source directory in that case.

Note

If the bundle contains a Pacemaker resource, Pacemaker will automatically map the equivalent of source-dir=/etc/pacemaker/authkeytarget-dir=/etc/pacemaker/authkey and source-dir-root=/var/log/pacemaker/bundlestarget-dir=/var/log into the container, so it is not necessary to specify those paths in when configuring storage-map parameters.

Important

The PCMK_authkey_location environment variable must not be set to anything other than the default of /etc/pacemaker/authkey on any node in the cluster.

9.5.2. Configuring a Pacemaker Resource in a Bundle

A bundle may optionally contain one Pacemaker cluster resource. As with a resource that is not contained in a bundle, the cluster resource may have operations, instance attributes, and metadata attributes defined. If a bundle contains a resource, the container image must include the Pacemaker Remote daemon, and ip-range-start or control-port must be configured in the bundle. Pacemaker will create an implicit ocf:pacemaker:remote resource for the connection, launch Pacemaker Remote within the container, and monitor and manage the resource by means of Pacemaker Remote. If the bundle has more than one container instance (replica), the Pacemaker resource will function as an implicit clone, which will be a multistate clone if the bundle has configured the promoted-max option as greater than zero.
You create a resource in a Pacemaker bundle with the pcs resource create command by specifying the bundle parameter for the command and the bundle ID in which to include the resource. For an example of creating a Pacemaker bundle that contains a resource, see Section 9.5.4, “Pacemaker Bundle Configuration Example”.

Important

Containers in bundles that contain a resource must have an accessible networking environment, so that Pacemaker on the cluster nodes can contact Pacemaker Remote inside the container. For example, the docker option --net=none should not be used with a resource. The default (using a distinct network space inside the container) works in combination with the ip-range-start parameter. If the docker option --net=host is used (making the container share the host’s network space), a unique control-port parameter should be specified for each bundle. Any firewall must allow access to the control-port.

9.5.2.1. Node Attributes and Bundle Resources

If the bundle contains a cluster resource, the resource agent may want to set node attributes such as master scores. However, with containers, it is not apparent which node should get the attribute.
If the container uses shared storage that is the same no matter which node the container is hosted on, then it is appropriate to use the master score on the bundle node itself. On the other hand, if the container uses storage exported from the underlying host, then it may be more appropriate to use the master score on the underlying host. Since this depends on the particular situation, the container-attribute-target resource metadata attribute allows the user to specify which approach to use. If it is set to host, then user-defined node attributes will be checked on the underlying host. If it is anything else, the local node (in this case the bundle node) is used. This behavior applies only to user-defined attributes; the cluster will always check the local node for cluster-defined attributes such as #uname.
If container-attribute-target is set to host, the cluster will pass additional environment variables to the resource agent that allow it to set node attributes appropriately.

9.5.2.2. Metadata Attributes and Bundle Resources

Any metadata attribute set on a bundle will be inherited by the resource contained in a bundle and any resources implicitly created by Pacemaker for the bundle. This includes options such as priority, target-role, and is-managed.

9.5.3. Limitations of Pacemaker Bundles

Pacemaker bundles operate with the following limitations:
  • Bundles may not be included in groups or explicitly cloned with a pcs command. This includes a resource that the bundle contains, and any resources implicitly created by Pacemaker for the bundle. Note, however, that if a bundle is configured with a value of replicas greater than one, the bundle behaves as if it were a clone.
  • Restarting Pacemaker while a bundle is unmanaged or the cluster is in maintenance mode may cause the bundle to fail.
  • Bundles do not have instance attributes, utilization attributes, or operations, although a resource contained in a bundle may have them.
  • A bundle that contains a resource can run on a Pacemaker Remote node only if the bundle uses a distinct control-port.

9.5.4. Pacemaker Bundle Configuration Example

The following example creates a Pacemaker bundle resource with a bundle ID of httpd-bundle that contains an ocf:heartbeat:apache resource with a resource ID of httpd.
This procedure requires the following prerequisite configuration:
  • Docker has been installed and enabled on every node in the cluster.
  • There is an existing Docker image, named pcmktest:http
  • The container image includes the Pacemaker Remote daemon.
  • The container image includes a configured Apache web server.
  • Every node in the cluster has directories /var/local/containers/httpd-bundle-0, /var/local/containers/httpd-bundle-1, and /var/local/containers/httpd-bundle-2, containing an index.html file for the web server root. In production, a single, shared document root would be more likely, but for the example this configuration allows you to make the index.html file on each host different so that you can connect to the web server and verify which index.html file is being served.
This procedure configures the following parameters for the Pacemaker bundle:
  • The bundle ID is httpd-bundle.
  • The previously-configured Docker container image is pcmktest:http.
  • This example will launch three container instances.
  • This example will pass the command-line option --log-driver=journald to the docker run command. This parameter is not required, but is included to show how to pass an extra option to the docker command. A value of --log-driver=journald means that the system logs inside the container will be logged in the underlying hosts's systemd journal.
  • Pacemaker will create three sequential implicit ocf:heartbeat:IPaddr2 resources, one for each container image, starting with the IP address 192.168.122.131.
  • The IP addresses are created on the host interface eth0.
  • The IP addresses are created with a CIDR netmask of 24.
  • This example creates a port map ID of http-port; connections to port 80 on the container's assigned IP address will be forwarded to the container network.
  • This example creates a storage map ID of httpd-root. For this storage mapping:
    • The value of source-dir-root is /var/local/containers, which specifies the start of the path on the host's file system that will be mapped into the container, using a different subdirectory on the host for each container instance.
    • The value of target-dir is /var/www/html, which specifies the path name within the container where the host storage will be mapped.
    • The file system rw mount option will be used when mapping the storage.
    • Since this example container includes a resource, Pacemaker will automatically map the equivalent of source-dir=/etc/pacemaker/authkey in the container, so you do not need to specify that path in the storage mapping.
In this example, the existing cluster configuration is put into a temporary file named temp-cib.xml, which is then copied to a file named temp-cib.xml.deltasrc. All modifications to the cluster configuration are made to the tmp-cib.xml file. When the udpates are complete, this procedure uses the diff-against option of the pcs cluster cib-push command so that only the updates to the configuration file are pushed to the active configuration file.
# pcs cluster cib tmp-cib.xml
# cp tmp-cib.xml tmp-cib.xml.deltasrc
# pcs -f tmp.cib.xml resource bundle create httpd-bundle \
container docker image=pcmktest:http replicas=3 \
options=--log-driver=journald \
network ip-range-start=192.168.122.131 host-interface=eth0 \
host-netmask=24 port-map id=httpd-port port=80 \
storage-map id=httpd-root source-dir-root=/var/local/containers \
target-dir=/var/www/html options=rw \
# pcs -f tmp-cib.xml resource create httpd ocf:heartbeat:apache \
statusurl=http://localhost/server-status bundle httpd-bundle
# pcs cluster cib-push tmp-cib.xml diff-against=tmp-cib.xml.deltasrc

9.6. Utilization and Placement Strategy

Pacemaker decides where to place a resource according to the resource allocation scores on every node. The resource will be allocated to the node where the resource has the highest score. This allocation score is derived from a combination of factors, including resource constraints, resource-stickiness settings, prior failure history of a resource on each node, and utilization of each node.
If the resource allocation scores on all the nodes are equal, by the default placement strategy Pacemaker will choose a node with the least number of allocated resources for balancing the load. If the number of resources on each node is equal, the first eligible node listed in the CIB will be chosen to run the resource.
Often, however, different resources use significantly different proportions of a node’s capacities (such as memory or I/O). You cannot always balance the load ideally by taking into account only the number of resources allocated to a node. In addition, if resources are placed such that their combined requirements exceed the provided capacity, they may fail to start completely or they may run run with degraded performance. To take these factors into account, Pacemaker allows you to configure the following components:
  • the capacity a particular node provides
  • the capacity a particular resource requires
  • an overall strategy for placement of resources
The following sections describe how to configure these components.

9.6.1. Utilization Attributes

To configure the capacity that a node provides or a resource requires, you can use utilization attributes for nodes and resources. You do this by setting a utilization variable for a resource and assigning a value to that variable to indicate what the resource requires, and then setting that same utilization variable for a node and assigning a value to that variable to indicate what that node provides.
You can name utilization attributes according to your preferences and define as many name and value pairs as your configuration needs. The values of utilization attributes must be integers.
As of Red Hat Enterprise Linux 7.3, you can set utilization attributes with the pcs command.
The following example configures a utilization attribute of CPU capacity for two nodes, setting this attribute as the variable cpu. It also configures a utilization attribute of RAM capacity, setting this attribute as the variable memory. In this example:
  • Node 1 is defined as providing a CPU capacity of two and a RAM capacity of 2048
  • Node 2 is defined as providing a CPU capacity of four and a RAM capacity of 2048
# pcs node utilization node1 cpu=2 memory=2048
# pcs node utilization node2 cpu=4 memory=2048
The following example specifies the same utilization attributes that three different resources require. In this example:
  • resource dummy-small requires a CPU capacity of 1 and a RAM capacity of 1024
  • resource dummy-medium requires a CPU capacity of 2 and a RAM capacity of 2048
  • resource dummy-large requires a CPU capacity of 1 and a RAM capacity of 3072
# pcs resource utilization dummy-small cpu=1 memory=1024
# pcs resource utilization dummy-medium cpu=2 memory=2048
# pcs resource utilization dummy-large cpu=3 memory=3072
A node is considered eligible for a resource if it has sufficient free capacity to satisfy the resource’s requirements, as defined by the utilization attributes.

9.6.2. Placement Strategy

After you have configured the capacities your nodes provide and the capacities your resources require, you need to set the placement-strategy cluster property, otherwise the capacity configurations have no effect. For information on setting cluster properties, see Chapter 12, Pacemaker Cluster Properties.
Four values are available for the placement-strategy cluster property:
  • default — Utilization values are not taken into account at all. Resources are allocated according to allocation scores. If scores are equal, resources are evenly distributed across nodes.
  • utilization — Utilization values are taken into account only when deciding whether a node is considered eligible (that is, whether it has sufficient free capacity to satisfy the resource’s requirements). Load-balancing is still done based on the number of resources allocated to a node.
  • balanced — Utilization values are taken into account when deciding whether a node is eligible to serve a resource and when load-balancing, so an attempt is made to spread the resources in a way that optimizes resource performance.
  • minimal — Utilization values are taken into account only when deciding whether a node is eligible to serve a resource. For load-balancing, an attempt is made to concentrate the resources on as few nodes as possible, thereby enabling possible power savings on the remaining nodes.
The following example command sets the value of placement-strategy to balanced. After running this command, Pacemaker will ensure the load from your resources will be distributed evenly throughout the cluster, without the need for complicated sets of colocation constraints.
# pcs property set placement-strategy=balanced

9.6.3. Resource Allocation

The following subsections summarize how Pacemaker allocates resources.

9.6.3.1. Node Preference

Pacemaker determines which node is preferred when allocating resources according to the following strategy.
  • The node with the highest node weight gets consumed first. Node weight is a score maintained by the cluster to represent node health.
  • If multiple nodes have the same node weight:
    • If the placement-strategy cluster property is default or utilization:
      • The node that has the least number of allocated resources gets consumed first.
      • If the numbers of allocated resources are equal, the first eligible node listed in the CIB gets consumed first.
    • If the placement-strategy cluster property is balanced:
      • The node that has the most free capacity gets consumed first.
      • If the free capacities of the nodes are equal, the node that has the least number of allocated resources gets consumed first.
      • If the free capacities of the nodes are equal and the number of allocated resources is equal, the first eligible node listed in the CIB gets consumed first.
    • If the placement-strategy cluster property is minimal, the first eligible node listed in the CIB gets consumed first.

9.6.3.2. Node Capacity

Pacemaker determines which node has the most free capacity according to the following strategy.
  • If only one type of utilization attribute has been defined, free capacity is a simple numeric comparison.
  • If multiple types of utilization attributes have been defined, then the node that is numerically highest in the most attribute types has the most free capacity. For example:
    • If NodeA has more free CPUs, and NodeB has more free memory, then their free capacities are equal.
    • If NodeA has more free CPUs, while NodeB has more free memory and storage, then NodeB has more free capacity.

9.6.3.3. Resource Allocation Preference

Pacemaker determines which resource is allocated first according to the following strategy.
  • The resource that has the highest priority gets allocated first. For information on setting priority for a resource, see Table 6.3, “Resource Meta Options”.
  • If the priorities of the resources are equal, the resource that has the highest score on the node where it is running gets allocated first, to prevent resource shuffling.
  • If the resource scores on the nodes where the resources are running are equal or the resources are not running, the resource that has the highest score on the preferred node gets allocated first. If the resource scores on the preferred node are equal in this case, the first runnable resource listed in the CIB gets allocated first.

9.6.4. Resource Placement Strategy Guidelines

To ensure that Pacemaker's placement strategy for resources works most effectively, you should take the following considerations into account when configuring your system.
  • Make sure that you have sufficient physical capacity.
    If the physical capacity of your nodes is being used to near maximum under normal conditions, then problems could occur during failover. Even without the utilization feature, you may start to experience timeouts and secondary failures.
  • Build some buffer into the capabilities you configure for the nodes.
    Advertise slightly more node resources than you physically have, on the assumption the that a Pacemaker resource will not use 100% of the configured amount of CPU, memory, and so forth all the time. This practice is sometimes called overcommit.
  • Specify resource priorities.
    If the cluster is going to sacrifice services, it should be the ones you care about least. Ensure that resource priorities are properly set so that your most important resources are scheduled first. For information on setting resource priorities, see Table 6.3, “Resource Meta Options”.

9.6.5. The NodeUtilization Resource Agent (Red Hat Enterprise Linux 7.4 and later)

Red Hat Enterprise Linux 7.4 supports the NodeUtilization resource agent. The NodeUtilization agent can detect the system parameters of available CPU, host memory availability, and hypervisor memory availability and add these parameters into the CIB. You can run the agent as a clone resource to have it automatically populate these parameters on each node.
For information on the NodeUtilization resource agent and the resource options for this agent, run the pcs resource describe NodeUtilization command.

9.7. Configuring Startup Order for Resource Dependencies not Managed by Pacemaker (Red Hat Enterprise Linux 7.4 and later)

It is possible for a cluster to include resources with dependencies that are not themselves managed by the cluster. In this case, you must ensure that those dependencies are started before Pacemaker is started and stopped after Pacemaker is stopped.
As of Red Hat Enterprise Linux 7.4, you can configure your startup order to account for this situation by means of the systemd resource-agents-deps target. You can create a systemd drop-in unit for this target and Pacemaker will order itself appropriately relative to this target.
For example, if a cluster includes a resource that depends on the external service foo that is not managed by the cluster, you can create the drop-in unit /etc/systemd/system/resource-agents-deps.target.d/foo.conf that contains the following:
[Unit]
Requires=foo.service
After=foo.service
After creating a drop-in unit, run the systemctl daemon-reload command.
A cluster dependency specified in this way can be something other than a service. For example, you may have a dependency on mounting a file system at /srv, in which case you would create a systemd file srv.mount for it according to the systemd documentation, then create a drop-in unit as described here with srv.mount in the .conf file instead of foo.service to make sure that Pacemaker starts after the disk is mounted.

9.8. Querying a Pacemaker Cluster with SNMP (Red Hat Enterprise Linux 7.5 and later)

As of Red Hat Enterprise Linux 7.5, you can use the pcs_snmp_agent daemon to query a Pacemaker cluster for data by means of SNMP. The pcs_snmp_agent daemon is an SNMP agent that connects to the master agent (snmpd) by means of agentx protocol. The pcs_snmp_agent agent does not work as a standalone agent as it only provides data to the master agent.
The following procedure sets up a basic configuration for a system to use SNMP with a Pacemaker cluster. You run this procedure on each node of the cluster from which you will be using SNMP to fetch data for the cluster.
  1. Install the pcs-snmp package on each node of the cluster. This will also install the net-snmp package which provides the snmp daemon.
    # yum install pcs-snmp
  2. Add the following line to the /etc/snmp/snmpd.conf configuration file to set up the snmpd daemon as master agentx.
    master agentx
    
  3. Add the following line to the /etc/snmp/snmpd.conf configuration file to enable pcs_snmp_agent in the same SNMP configuration.
    view    systemview    included   .1.3.6.1.4.1.32723.100
    
  4. Start the pcs_snmp_agent service.
    # systemctl start pcs_snmp_agent.service
    # systemctl enable pcs_snmp_agent.service
  5. To check the configuration, display the status of the cluster with the pcs status and then try to fetch the data from SNMP to check whether it corresponds to the output. Note that when you use SNMP to fetch data, only primitive resources are provided.
    The following example shows the output of a pcs status command on a running cluster with one failed action.
    # pcs status
    Cluster name: rhel75-cluster
    Stack: corosync
    Current DC: rhel75-node2 (version 1.1.18-5.el7-1a4ef7d180) - partition with quorum
    Last updated: Wed Nov 15 16:07:44 2017
    Last change: Wed Nov 15 16:06:40 2017 by hacluster via cibadmin on rhel75-node1
    
    2 nodes configured
    14 resources configured (1 DISABLED)
    
    Online: [ rhel75-node1 rhel75-node2 ]
    
    Full list of resources:
    
     fencing        (stonith:fence_xvm):    Started rhel75-node1
     dummy5 (ocf::pacemaker:Dummy): Stopped (disabled)
     dummy6 (ocf::pacemaker:Dummy): Stopped
     dummy7 (ocf::pacemaker:Dummy): Started rhel75-node2
     dummy8 (ocf::pacemaker:Dummy): Started rhel75-node1
     dummy9 (ocf::pacemaker:Dummy): Started rhel75-node2
     Resource Group: group1
         dummy1     (ocf::pacemaker:Dummy): Started rhel75-node1
         dummy10    (ocf::pacemaker:Dummy): Started rhel75-node1
     Clone Set: group2-clone [group2]
         Started: [ rhel75-node1 rhel75-node2 ]
     Clone Set: dummy4-clone [dummy4]
         Started: [ rhel75-node1 rhel75-node2 ]
    
    Failed Actions:
    * dummy6_start_0 on rhel75-node1 'unknown error' (1): call=87, status=complete, exitreason='',
        last-rc-change='Wed Nov 15 16:05:55 2017', queued=0ms, exec=20ms
    
    # snmpwalk -v 2c -c public localhost PACEMAKER-PCS-V1-MIB::pcmkPcsV1Cluster
    PACEMAKER-PCS-V1-MIB::pcmkPcsV1ClusterName.0 = STRING: "rhel75-cluster"
    PACEMAKER-PCS-V1-MIB::pcmkPcsV1ClusterQuorate.0 = INTEGER: 1
    PACEMAKER-PCS-V1-MIB::pcmkPcsV1ClusterNodesNum.0 = INTEGER: 2
    PACEMAKER-PCS-V1-MIB::pcmkPcsV1ClusterNodesNames.0 = STRING: "rhel75-node1"
    PACEMAKER-PCS-V1-MIB::pcmkPcsV1ClusterNodesNames.1 = STRING: "rhel75-node2"
    PACEMAKER-PCS-V1-MIB::pcmkPcsV1ClusterCorosyncNodesOnlineNum.0 = INTEGER: 2
    PACEMAKER-PCS-V1-MIB::pcmkPcsV1ClusterCorosyncNodesOnlineNames.0 = STRING: "rhel75-node1"
    PACEMAKER-PCS-V1-MIB::pcmkPcsV1ClusterCorosyncNodesOnlineNames.1 = STRING: "rhel75-node2"
    PACEMAKER-PCS-V1-MIB::pcmkPcsV1ClusterCorosyncNodesOfflineNum.0 = INTEGER: 0
    PACEMAKER-PCS-V1-MIB::pcmkPcsV1ClusterPcmkNodesOnlineNum.0 = INTEGER: 2
    PACEMAKER-PCS-V1-MIB::pcmkPcsV1ClusterPcmkNodesOnlineNames.0 = STRING: "rhel75-node1"
    PACEMAKER-PCS-V1-MIB::pcmkPcsV1ClusterPcmkNodesOnlineNames.1 = STRING: "rhel75-node2"
    PACEMAKER-PCS-V1-MIB::pcmkPcsV1ClusterPcmkNodesStandbyNum.0 = INTEGER: 0
    PACEMAKER-PCS-V1-MIB::pcmkPcsV1ClusterPcmkNodesOfflineNum.0 = INTEGER: 0
    PACEMAKER-PCS-V1-MIB::pcmkPcsV1ClusterAllResourcesNum.0 = INTEGER: 11
    PACEMAKER-PCS-V1-MIB::pcmkPcsV1ClusterAllResourcesIds.0 = STRING: "fencing"
    PACEMAKER-PCS-V1-MIB::pcmkPcsV1ClusterAllResourcesIds.1 = STRING: "dummy5"
    PACEMAKER-PCS-V1-MIB::pcmkPcsV1ClusterAllResourcesIds.2 = STRING: "dummy6"
    PACEMAKER-PCS-V1-MIB::pcmkPcsV1ClusterAllResourcesIds.3 = STRING: "dummy7"
    PACEMAKER-PCS-V1-MIB::pcmkPcsV1ClusterAllResourcesIds.4 = STRING: "dummy8"
    PACEMAKER-PCS-V1-MIB::pcmkPcsV1ClusterAllResourcesIds.5 = STRING: "dummy9"
    PACEMAKER-PCS-V1-MIB::pcmkPcsV1ClusterAllResourcesIds.6 = STRING: "dummy1"
    PACEMAKER-PCS-V1-MIB::pcmkPcsV1ClusterAllResourcesIds.7 = STRING: "dummy10"
    PACEMAKER-PCS-V1-MIB::pcmkPcsV1ClusterAllResourcesIds.8 = STRING: "dummy2"
    PACEMAKER-PCS-V1-MIB::pcmkPcsV1ClusterAllResourcesIds.9 = STRING: "dummy3"
    PACEMAKER-PCS-V1-MIB::pcmkPcsV1ClusterAllResourcesIds.10 = STRING: "dummy4"
    PACEMAKER-PCS-V1-MIB::pcmkPcsV1ClusterRunningResourcesNum.0 = INTEGER: 9
    PACEMAKER-PCS-V1-MIB::pcmkPcsV1ClusterRunningResourcesIds.0 = STRING: "fencing"
    PACEMAKER-PCS-V1-MIB::pcmkPcsV1ClusterRunningResourcesIds.1 = STRING: "dummy7"
    PACEMAKER-PCS-V1-MIB::pcmkPcsV1ClusterRunningResourcesIds.2 = STRING: "dummy8"
    PACEMAKER-PCS-V1-MIB::pcmkPcsV1ClusterRunningResourcesIds.3 = STRING: "dummy9"
    PACEMAKER-PCS-V1-MIB::pcmkPcsV1ClusterRunningResourcesIds.4 = STRING: "dummy1"
    PACEMAKER-PCS-V1-MIB::pcmkPcsV1ClusterRunningResourcesIds.5 = STRING: "dummy10"
    PACEMAKER-PCS-V1-MIB::pcmkPcsV1ClusterRunningResourcesIds.6 = STRING: "dummy2"
    PACEMAKER-PCS-V1-MIB::pcmkPcsV1ClusterRunningResourcesIds.7 = STRING: "dummy3"
    PACEMAKER-PCS-V1-MIB::pcmkPcsV1ClusterRunningResourcesIds.8 = STRING: "dummy4"
    PACEMAKER-PCS-V1-MIB::pcmkPcsV1ClusterStoppedResroucesNum.0 = INTEGER: 1
    PACEMAKER-PCS-V1-MIB::pcmkPcsV1ClusterStoppedResroucesIds.0 = STRING: "dummy5"
    PACEMAKER-PCS-V1-MIB::pcmkPcsV1ClusterFailedResourcesNum.0 = INTEGER: 1
    PACEMAKER-PCS-V1-MIB::pcmkPcsV1ClusterFailedResourcesIds.0 = STRING: "dummy6"
    PACEMAKER-PCS-V1-MIB::pcmkPcsV1ClusterFailedResourcesIds.0 = No more variables left in this MIB View (It is past the end of the MIB tree)
    

Chapter 10. Cluster Quorum

A Red Hat Enterprise Linux High Availability Add-On cluster uses the votequorum service, in conjunction with fencing, to avoid split brain situations. A number of votes is assigned to each system in the cluster, and cluster operations are allowed to proceed only when a majority of votes is present. The service must be loaded into all nodes or none; if it is loaded into a subset of cluster nodes, the results will be unpredictable. For information on the configuration and operation of the votequorum service, see the votequorum(5) man page.

10.1. Configuring Quorum Options

There are some special features of quorum configuration that you can set when you create a cluster with the pcs cluster setup command. Table 10.1, “Quorum Options” summarizes these options.

Table 10.1. Quorum Options

OptionDescription
--auto_tie_breaker
When enabled, the cluster can suffer up to 50% of the nodes failing at the same time, in a deterministic fashion. The cluster partition, or the set of nodes that are still in contact with the nodeid configured in auto_tie_breaker_node (or lowest nodeid if not set), will remain quorate. The other nodes will be inquorate.
The auto_tie_breaker option is principally used for clusters with an even number of nodes, as it allows the cluster to continue operation with an even split. For more complex failures, such as multiple, uneven splits, it is recommended that you use a quorum device, as described in Section 10.5, “Quorum Devices”. The auto_tie_breaker option is incompatible with quorum devices.
--wait_for_all
When enabled, the cluster will be quorate for the first time only after all nodes have been visible at least once at the same time.
The wait_for_all option is primarily used for two-node clusters and for even-node clusters using the quorum device lms (last man standing) algorithm.
The wait_for_all option is automatically enabled when a cluster has two nodes, does not use a quorum device, and auto_tie_breaker is disabled. You can override this by explicitly setting wait_for_all to 0.
--last_man_standing When enabled, the cluster can dynamically recalculate expected_votes and quorum under specific circumstances. You must enable wait_for_all when you enable this option. The last_man_standing option is incompatible with quorum devices.
--last_man_standing_window The time, in milliseconds, to wait before recalculating expected_votes and quorum after a cluster loses nodes.
For further information about configuring and using these options, see the votequorum(5) man page.

10.2. Quorum Administration Commands (Red Hat Enterprise Linux 7.3 and Later)

Once a cluster is running, you can enter the following cluster quorum commands.
The following command shows the quorum configuration.
pcs quorum [config]
The following command shows the quorum runtime status.
pcs quorum status
If you take nodes out of a cluster for a long period of time and the loss of those nodes would cause quorum loss, you can change the value of the expected_votes parameter for the live cluster with the pcs quorum expected-votes command. This allows the cluster to continue operation when it does not have quorum.

Warning

Changing the expected votes in a live cluster should be done with extreme caution. If less than 50% of the cluster is running because you have manually changed the expected votes, then the other nodes in the cluster could be started separately and run cluster services, causing data corruption and other unexpected results. If you change this value, you should ensure that the wait_for_all parameter is enabled.
The following command sets the expected votes in the live cluster to the specified value. This affects the live cluster only and does not change the configuration file; the value of expected_votes is reset to the value in the configuration file in the event of a reload.
pcs quorum expected-votes votes

10.3. Modifying Quorum Options (Red Hat Enterprise Linux 7.3 and later)

As of Red Hat Enterprise Linux 7.3, you can modify general quorum options for your cluster with the pcs quorum update command. Executing this command requires that the cluster be stopped. For information on the quorum options, see the votequorum(5) man page.
The format of the pcs quorum update command is as follows.
pcs quorum update [auto_tie_breaker=[0|1]] [last_man_standing=[0|1]] [last_man_standing_window=[time-in-ms] [wait_for_all=[0|1]]
The following series of commands modifies the wait_for_all quorum option and displays the updated status of the option. Note that the system does not allow you to execute this command while the cluster is running.
[root@node1:~]# pcs quorum update wait_for_all=1
Checking corosync is not running on nodes...
Error: node1: corosync is running
Error: node2: corosync is running

[root@node1:~]# pcs cluster stop --all
node2: Stopping Cluster (pacemaker)...
node1: Stopping Cluster (pacemaker)...
node1: Stopping Cluster (corosync)...
node2: Stopping Cluster (corosync)...

[root@node1:~]# pcs quorum update wait_for_all=1
Checking corosync is not running on nodes...
node2: corosync is not running
node1: corosync is not running
Sending updated corosync.conf to nodes...
node1: Succeeded
node2: Succeeded

[root@node1:~]# pcs quorum config
Options:
  wait_for_all: 1

10.4. The quorum unblock Command

In a situation in which you know that the cluster is inquorate but you want the cluster to proceed with resource management, you can use the following command to prevent the cluster from waiting for all nodes when establishing quorum.

Note

This command should be used with extreme caution. Before issuing this command, it is imperative that you ensure that nodes that are not currently in the cluster are switched off and have no access to shared resources.
# pcs cluster quorum unblock

10.5. Quorum Devices

Red Hat Enterprise Linux 7.4 provides full support for the ability to configure a separate quorum device which acts as a third-party arbitration device for the cluster. Its primary use is to allow a cluster to sustain more node failures than standard quorum rules allow. A quorum device is recommended for clusters with an even number of nodes and highly recommended for two-node clusters.
You must take the following into account when configuring a quorum device.
  • It is recommended that a quorum device be run on a different physical network at the same site as the cluster that uses the quorum device. Ideally, the quorum device host should be in a separate rack than the main cluster, or at least on a separate PSU and not on the same network segment as the corosync ring or rings.
  • You cannot use more than one quorum device in a cluster at the same time.
  • Although you cannot use more than one quorum device in a cluster at the same time, a single quorum device may be used by several clusters at the same time. Each cluster using that quorum device can use different algorithms and quorum options, as those are stored on the cluster nodes themselves. For example, a single quorum device can be used by one cluster with an ffsplit (fifty/fifty split) algorithm and by a second cluster with an lms (last man standing) algorithm.
  • A quorum device should not be run on an existing cluster node.

10.5.1. Installing Quorum Device Packages

Configuring a quorum device for a cluster requires that you install the following packages:
  • Install corosync-qdevice on the nodes of an existing cluster.
    [root@node1:~]# yum install corosync-qdevice
    [root@node2:~]# yum install corosync-qdevice
  • Install pcs and corosync-qnetd on the quorum device host.
    [root@qdevice:~]# yum install pcs corosync-qnetd
  • Start the pcsd service and enable pcsd at system start on the quorum device host.
    [root@qdevice:~]# systemctl start pcsd.service
    [root@qdevice:~]# systemctl enable pcsd.service

10.5.2. Configuring a Quorum Device

This section provides a sample procedure to configure a quorum device in a Red Hat high availability cluster. The following procedure configures a quorum device and adds it to the cluster. In this example:
  • The node used for a quorum device is qdevice.
  • The quorum device model is net, which is currently the only supported model. The net model supports the following algorithms:
    • ffsplit: fifty-fifty split. This provides exactly one vote to the partition with the highest number of active nodes.
    • lms: last-man-standing. If the node is the only one left in the cluster that can see the qnetd server, then it returns a vote.

      Warning

      The LMS algorithm allows the cluster to remain quorate even with only one remaining node, but it also means that the voting power of the quorum device is great since it is the same as number_of_nodes - 1. Losing connection with the quorum device means losing number_of_nodes - 1 votes, which means that only a cluster with all nodes active can remain quorate (by overvoting the quorum device); any other cluster becomes inquorate.
    For more detailed information on the implementation of these algorithms, see the corosync-qdevice(8) man page.
  • The cluster nodes are node1 and node2.
The following procedure configures a quorum device and adds that quorum device to a cluster.
  1. On the node that you will use to host your quorum device, configure the quorum device with the following command. This command configures and starts the quorum device model net and configures the device to start on boot.
    [root@qdevice:~]# pcs qdevice setup model net --enable --start
    Quorum device 'net' initialized
    quorum device enabled
    Starting quorum device...
    quorum device started
    
    After configuring the quorum device, you can check its status. This should show that the corosync-qnetd daemon is running and, at this point, there are no clients connected to it. The --full command option provides detailed output.
    [root@qdevice:~]# pcs qdevice status net --full
    QNetd address:                  *:5403
    TLS:                            Supported (client certificate required)
    Connected clients:              0
    Connected clusters:             0
    Maximum send/receive size:      32768/32768 bytes
    
  2. Enable the ports on the firewall needed by the pcsd daemon and the net quorum device by enabling the high-availability service on firewalld with following commands.
    [root@qdevice:~]# firewall-cmd --permanent --add-service=high-availability
    [root@qdevice:~]# firewall-cmd --add-service=high-availability
  3. From one of the nodes in the existing cluster, authenticate user hacluster on the node that is hosting the quorum device.
    [root@node1:~] # pcs cluster auth qdevice
    Username: hacluster
    Password:
    qdevice: Authorized
    
  4. Add the quorum device to the cluster.
    Before adding the quorum device, you can check the current configuration and status for the quorum device for later comparison. The output for these commands indicates that the cluster is not yet using a quorum device.
    [root@node1:~]# pcs quorum config
    Options:
    
    [root@node1:~]# pcs quorum status
    Quorum information
    ------------------
    Date:             Wed Jun 29 13:15:36 2016
    Quorum provider:  corosync_votequorum
    Nodes:            2
    Node ID:          1
    Ring ID:          1/8272
    Quorate:          Yes
    
    Votequorum information
    ----------------------
    Expected votes:   2
    Highest expected: 2
    Total votes:      2
    Quorum:           1  
    Flags:            2Node Quorate 
    
    Membership information
    ----------------------
        Nodeid      Votes    Qdevice Name
             1          1         NR node1 (local)
             2          1         NR node2
    
    
    The following command adds the quorum device that you have previously created to the cluster. You cannot use more than one quorum device in a cluster at the same time. However, one quorum device can be used by several clusters at the same time. This example command configures the quorum device to use the ffsplit algorithm. For information on the configuration options for the quorum device, see the corosync-qdevice(8) man page.
    [root@node1:~]# pcs quorum device add model net host=qdevice algorithm=ffsplit
    Setting up qdevice certificates on nodes...
    node2: Succeeded
    node1: Succeeded
    Enabling corosync-qdevice...
    node1: corosync-qdevice enabled
    node2: corosync-qdevice enabled
    Sending updated corosync.conf to nodes...
    node1: Succeeded
    node2: Succeeded
    Corosync configuration reloaded
    Starting corosync-qdevice...
    node1: corosync-qdevice started
    node2: corosync-qdevice started
    
  5. Check the configuration status of the quorum device.
    From the cluster side, you can execute the following commands to see how the configuration has changed.
    The pcs quorum config shows the quorum device that has been configured.
    [root@node1:~]# pcs quorum config
    Options:
    Device:
      Model: net
        algorithm: ffsplit
        host: qdevice
    
    The pcs quorum status command shows the quorum runtime status, indicating that the quorum device is in use.
    [root@node1:~]# pcs quorum status
    Quorum information
    ------------------
    Date:             Wed Jun 29 13:17:02 2016
    Quorum provider:  corosync_votequorum
    Nodes:            2
    Node ID:          1
    Ring ID:          1/8272
    Quorate:          Yes
    
    Votequorum information
    ----------------------
    Expected votes:   3
    Highest expected: 3
    Total votes:      3
    Quorum:           2  
    Flags:            Quorate Qdevice 
    
    Membership information
    ----------------------
        Nodeid      Votes    Qdevice Name
             1          1    A,V,NMW node1 (local)
             2          1    A,V,NMW node2
             0          1            Qdevice
    
    The pcs quorum device status shows the quorum device runtime status.
    [root@node1:~]# pcs quorum device status
    Qdevice information
    -------------------
    Model:                  Net
    Node ID:                1
    Configured node list:
        0   Node ID = 1
        1   Node ID = 2
    Membership node list:   1, 2
    
    Qdevice-net information
    ----------------------
    Cluster name:           mycluster
    QNetd host:             qdevice:5403
    Algorithm:              ffsplit
    Tie-breaker:            Node with lowest node ID
    State:                  Connected
    
    From the quorum device side, you can execute the following status command, which shows the status of the corosync-qnetd daemon.
    [root@qdevice:~]# pcs qdevice status net --full
    QNetd address:                  *:5403
    TLS:                            Supported (client certificate required)
    Connected clients:              2
    Connected clusters:             1
    Maximum send/receive size:      32768/32768 bytes
    Cluster "mycluster":
        Algorithm:          ffsplit
        Tie-breaker:        Node with lowest node ID
        Node ID 2:
            Client address:         ::ffff:192.168.122.122:50028
            HB interval:            8000ms
            Configured node list:   1, 2
            Ring ID:                1.2050
            Membership node list:   1, 2
            TLS active:             Yes (client certificate verified)
            Vote:                   ACK (ACK)
        Node ID 1:
            Client address:         ::ffff:192.168.122.121:48786
            HB interval:            8000ms
            Configured node list:   1, 2
            Ring ID:                1.2050
            Membership node list:   1, 2
            TLS active:             Yes (client certificate verified)
            Vote:                   ACK (ACK)
    

10.5.3. Managing the Quorum Device Service

PCS provides the ability to manage the quorum device service on the local host (corosync-qnetd), as shown in the following example commands. Note that these commands affect only the corosync-qnetd service.
[root@qdevice:~]# pcs qdevice start net
[root@qdevice:~]# pcs qdevice stop net
[root@qdevice:~]# pcs qdevice enable net
[root@qdevice:~]# pcs qdevice disable net
[root@qdevice:~]# pcs qdevice kill net

10.5.4. Managing the Quorum Device Settings in a Cluster

The following sections describe the PCS commands that you can use to manage the quorum device settings in a cluster, showing examples that are based on the quorum device configuration in Section 10.5.2, “Configuring a Quorum Device”.

10.5.4.1. Changing Quorum Device Settings

You can change the setting of a quorum device with the pcs quorum device update command.

Warning

To change the host option of quorum device model net, use the pcs quorum device remove and the pcs quorum device add commands to set up the configuration properly, unless the old and the new host are the same machine.
The following command changes the quorum device algorithm to lms.
[root@node1:~]# pcs quorum device update model algorithm=lms
Sending updated corosync.conf to nodes...
node1: Succeeded
node2: Succeeded
Corosync configuration reloaded
Reloading qdevice configuration on nodes...
node1: corosync-qdevice stopped
node2: corosync-qdevice stopped
node1: corosync-qdevice started
node2: corosync-qdevice started

10.5.4.2. Removing a Quorum Device

Use the following command to remove a quorum device configured on a cluster node.
[root@node1:~]# pcs quorum device remove
Sending updated corosync.conf to nodes...
node1: Succeeded
node2: Succeeded
Corosync configuration reloaded
Disabling corosync-qdevice...
node1: corosync-qdevice disabled
node2: corosync-qdevice disabled
Stopping corosync-qdevice...
node1: corosync-qdevice stopped
node2: corosync-qdevice stopped
Removing qdevice certificates from nodes...
node1: Succeeded
node2: Succeeded
After you have removed a quorum device, you should see the following error message when displaying the quorum device status.
[root@node1:~]# pcs quorum device status
Error: Unable to get quorum status: corosync-qdevice-tool: Can't connect to QDevice socket (is QDevice running?): No such file or directory

10.5.4.3. Destroying a Quorum Device

To disable and stop a quorum device on the quorum device host and delete all of its configuration files, use the following command.
[root@qdevice:~]# pcs qdevice destroy net
Stopping quorum device...
quorum device stopped
quorum device disabled
Quorum device 'net' configuration files removed

Chapter 11. Pacemaker Rules

Rules can be used to make your configuration more dynamic. One use of rules might be to assign machines to different processing groups (using a node attribute) based on time and to then use that attribute when creating location constraints.
Each rule can contain a number of expressions, date-expressions and even other rules. The results of the expressions are combined based on the rule's boolean-op field to determine if the rule ultimately evaluates to true or false. What happens next depends on the context in which the rule is being used.

Table 11.1. Properties of a Rule

FieldDescription
role
Limits the rule to apply only when the resource is in that role. Allowed values: Started, Slave, and Master. NOTE: A rule with role="Master" cannot determine the initial location of a clone instance. It will only affect which of the active instances will be promoted.
score
The score to apply if the rule evaluates to true. Limited to use in rules that are part of location constraints.
score-attribute
The node attribute to look up and use as a score if the rule evaluates to true. Limited to use in rules that are part of location constraints.
boolean-op
How to combine the result of multiple expression objects. Allowed values: and and or. The default value is and.

11.1. Node Attribute Expressions

Node attribute expressions are used to control a resource based on the attributes defined by a node or nodes.

Table 11.2. Properties of an Expression

FieldDescription
attribute
The node attribute to test
type
Determines how the value(s) should be tested. Allowed values: string, integer, version. The default value is string
operation
The comparison to perform. Allowed values:
* lt - True if the node attribute’s value is less than value
* gt - True if the node attribute’s value is greater than value
* lte - True if the node attribute’s value is less than or equal to value
* gte - True if the node attribute’s value is greater than or equal to value
* eq - True if the node attribute’s value is equal to value
* ne - True if the node attribute’s value is not equal to value
* defined - True if the node has the named attribute
* not_defined - True if the node does not have the named attribute
value
User supplied value for comparison (required)
In addition to any attributes added by the administrator, the cluster defines special, built-in node attributes for each node that can also be used, as described in Table 11.3, “Built-in Node Attributes”.

Table 11.3. Built-in Node Attributes

NameDescription
#uname
Node name
#id
Node ID
#kind
Node type. Possible values are cluster, remote, and container. The value of kind is remote. for Pacemaker Remote nodes created with the ocf:pacemaker:remote resource, and container for Pacemaker Remote guest nodes and bundle nodes.
#is_dc
true if this node is a Designated Controller (DC), false otherwise
#cluster_name
The value of the cluster-name cluster property, if set
#site_name
The value of the site-name node attribute, if set, otherwise identical to #cluster-name
#role
The role the relevant multistate resource has on this node. Valid only within a rule for a location constraint for a multistate resource.

11.2. Time/Date Based Expressions

Date expressions are used to control a resource or cluster option based on the current date/time. They can contain an optional date specification.

Table 11.4. Properties of a Date Expression

FieldDescription
start
A date/time conforming to the ISO8601 specification.
end
A date/time conforming to the ISO8601 specification.
operation
Compares the current date/time with the start or the end date or both the start and end date, depending on the context. Allowed values:
* gt - True if the current date/time is after start
* lt - True if the current date/time is before end
* in-range - True if the current date/time is after start and before end
* date-spec - performs a cron-like comparison to the current date/time

11.3. Date Specifications

Date specifications are used to create cron-like expressions relating to time. Each field can contain a single number or a single range. Instead of defaulting to zero, any field not supplied is ignored.
For example, monthdays="1" matches the first day of every month and hours="09-17" matches the hours between 9 am and 5 pm (inclusive). However, you cannot specify weekdays="1,2" or weekdays="1-2,5-6" since they contain multiple ranges.

Table 11.5. Properties of a Date Specification

FieldDescription
id
A unique name for the date
hours
Allowed values: 0-23
monthdays
Allowed values: 0-31 (depending on month and year)
weekdays
Allowed values: 1-7 (1=Monday, 7=Sunday)
yeardays
Allowed values: 1-366 (depending on the year)
months
Allowed values: 1-12
weeks
Allowed values: 1-53 (depending on weekyear)
years
Year according the Gregorian calendar
weekyears
May differ from Gregorian years; for example, 2005-001 Ordinal is also 2005-01-01 Gregorian is also 2004-W53-6 Weekly
moon
Allowed values: 0-7 (0 is new, 4 is full moon).

11.4. Durations

Durations are used to calculate a value for end when one is not supplied to in_range operations. They contain the same fields as date_spec objects but without the limitations (ie. you can have a duration of 19 months). Like date_specs, any field not supplied is ignored.

11.5. Configuring Rules with pcs

To configure a rule using pcs, you can configure a location constraint that uses rules, as described in Section 7.1.3, “Using Rules to Determine Resource Location”.
To remove a rule, use the following. If the rule that you are removing is the last rule in its constraint, the constraint will be removed.
pcs constraint rule remove rule_id

Chapter 12. Pacemaker Cluster Properties

Cluster properties control how the cluster behaves when confronted with situations that may occur during cluster operation.

12.1. Summary of Cluster Properties and Options

Table 12.1, “Cluster Properties” summaries the Pacemaker cluster properties, showing the default values of the properties and the possible values you can set for those properties.

Note

In addition to the properties described in this table, there are additional cluster properties that are exposed by the cluster software. For these properties, it is recommended that you not change their values from their defaults.

Table 12.1. Cluster Properties

OptionDefaultDescription
batch-limit0
The number of jobs that the transition engine (TE) is allowed to execute in parallel. The "correct" value will depend on the speed and load of your network and cluster nodes.
migration-limit-1 (unlimited)
The number of migration jobs that the TE is allowed to execute in parallel on a node.
no-quorum-policystop
What to do when the cluster does not have quorum. Allowed values:
* ignore - continue all resource management
* freeze - continue resource management, but do not recover resources from nodes not in the affected partition
* stop - stop all resources in the affected cluster partition
* suicide - fence all nodes in the affected cluster partition
symmetric-clustertrue
Indicates whether resources can run on any node by default.
stonith-enabledtrue
Indicates that failed nodes and nodes with resources that cannot be stopped should be fenced. Protecting your data requires that you set this true.
If true, or unset, the cluster will refuse to start resources unless one or more STONITH resources have been configured also.
stonith-actionreboot
Action to send to STONITH device. Allowed values: reboot, off. The value poweroff is also allowed, but is only used for legacy devices.
cluster-delay60s
Round trip delay over the network (excluding action execution). The "correct" value will depend on the speed and load of your network and cluster nodes.
stop-orphan-resourcestrue
Indicates whether deleted resources should be stopped.
stop-orphan-actionstrue
Indicates whether deleted actions should be canceled.
start-failure-is-fataltrue
Indicates whether a failure to start a resource on a particular node prevents further start attempts on that node. When set to false, the cluster will decide whether to try starting on the same node again based on the resource's current failure count and migration threshold. For information on setting the migration-threshold option for a resource, see Section 8.2, “Moving Resources Due to Failure”.
Setting start-failure-is-fatal to false incurs the risk that this will allow one faulty node that is unable to start a resource to hold up all dependent actions. This is why start-failure-is-fatal defaults to true. The risk of setting start-failure-is-fatal=false can be mitigated by setting a low migration threshold so that other actions can proceed after that many failures.
pe-error-series-max-1 (all)
The number of PE inputs resulting in ERRORs to save. Used when reporting problems.
pe-warn-series-max-1 (all)
The number of PE inputs resulting in WARNINGs to save. Used when reporting problems.
pe-input-series-max-1 (all)
The number of "normal" PE inputs to save. Used when reporting problems.
cluster-infrastructure 
The messaging stack on which Pacemaker is currently running. Used for informational and diagnostic purposes; not user-configurable.
dc-version 
Version of Pacemaker on the cluster's Designated Controller (DC). Used for diagnostic purposes; not user-configurable.
last-lrm-refresh 
Last refresh of the Local Resource Manager, given in units of seconds since epoca. Used for diagnostic purposes; not user-configurable.
cluster-recheck-interval15 minutes
Polling interval for time-based changes to options, resource parameters and constraints. Allowed values: Zero disables polling, positive values are an interval in seconds (unless other SI units are specified, such as 5min).
maintenance-modefalse
Maintenance Mode tells the cluster to go to a "hands off" mode, and not start or stop any services until told otherwise. When maintenance mode is completed, the cluster does a sanity check of the current state of any services, and then stops or starts any that need it.
shutdown-escalation20min
The time after which to give up trying to shut down gracefully and just exit. Advanced use only.
stonith-timeout60s
How long to wait for a STONITH action to complete.
stop-all-resourcesfalse
Should the cluster stop all resources.
enable-aclfalse
(Red Hat Enterprise Linux 7.1 and later) Indicates whether the cluster can use access control lists, as set with the pcs acl command.
placement-strategydefault
Indicates whether and how the cluster will take utilization attributes into account when determining resource placement on cluster nodes. For information on utilization attributes and placement strategies, see Section 9.6, “Utilization and Placement Strategy”.

12.2. Setting and Removing Cluster Properties

To set the value of a cluster property, use the following pcs command.
pcs property set property=value
For example, to set the value of symmetric-cluster to false, use the following command.
# pcs property set symmetric-cluster=false
You can remove a cluster property from the configuration with the following command.
pcs property unset property
Alternately, you can remove a cluster property from a configuration by leaving the value field of the pcs property set command blank. This restores that property to its default value. For example, if you have previously set the symmetric-cluster property to false, the following command removes the value you have set from the configuration and restores the value of symmetric-cluster to true, which is its default value.
# pcs property set symmetic-cluster=

12.3. Querying Cluster Property Settings

In most cases, when you use the pcs command to display values of the various cluster components, you can use pcs list or pcs show interchangeably. In the following examples, pcs list is the format used to display an entire list of all settings for more than one property, while pcs show is the format used to display the values of a specific property.
To display the values of the property settings that have been set for the cluster, use the following pcs command.
pcs property list
To display all of the values of the property settings for the cluster, including the default values of the property settings that have not been explicitly set, use the following command.
pcs property list --all
To display the current value of a specific cluster property, use the following command.
pcs property show property
For example, to display the current value of the cluster-infrastructure property, execute the following command:
# pcs property show cluster-infrastructure
Cluster Properties:
 cluster-infrastructure: cman
For informational purposes, you can display a list of all of the default values for the properties, whether they have been set to a value other than the default or not, by using the following command.
pcs property [list|show] --defaults

Chapter 13. Triggering Scripts for Cluster Events

A Pacemaker cluster is an event-driven system, where an event might be a resource or node failure, a configuration change, or a resource starting or stopping. You can configure Pacemaker cluster alerts to take some external action when a cluster event occurs. You can configure cluster alerts in one of two ways:
  • As of Red Hat Enterprise Linux 7.3, you can configure Pacemaker alerts by means of alert agents, which are external programs that the cluster calls in the same manner as the cluster calls resource agents to handle resource configuration and operation. This is the preferred, simpler method of configuring cluster alerts. Pacemaker alert agents are described in Section 13.1, “Pacemaker Alert Agents (Red Hat Enterprise Linux 7.3 and later)”.
  • The ocf:pacemaker:ClusterMon resource can monitor the cluster status and trigger alerts on each cluster event. This resource runs the crm_mon command in the background at regular intervals. For information on the ClusterMon resource see Section 13.2, “Event Notification with Monitoring Resources”.

13.1. Pacemaker Alert Agents (Red Hat Enterprise Linux 7.3 and later)

You can create Pacemaker alert agents to take some external action when a cluster event occurs. The cluster passes information about the event to the agent by means of environment variables. Agents can do anything with this information, such as send an email message or log to a file or update a monitoring system.

13.1.1. Using the Sample Alert Agents

When you use one of sample alert agents, you should review the script to ensure that it suits your needs. These sample agents are provided as a starting point for custom scripts for specific cluster environments.
To use one of the sample alert agents, you must install the agent on each node in the cluster. For example, the following command installs the alert_file.sh.sample script as alert_file.sh.
# install --mode=0755 /usr/share/pacemaker/alerts/alert_file.sh.sample /var/lib/pacemaker/alert_file.sh
After you have installed the script, you can create an alert that uses the script.
The following example configures an alert that uses the installed alert_file.sh alert agent to log events to a file. Alert agents run as the user hacluster, which has a minimal set of permissions.
This example creates the log file pcmk_alert_file.log that will be used to record the events. It then creates the alert agent and adds the path to the log file as its recipient.
# touch /var/log/pcmk_alert_file.log
# chown hacluster:haclient /var/log/pcmk_alert_file.log
# chmod 600 /var/log/pcmk_alert_file.log 
# pcs alert create id=alert_file description="Log events to a file." path=/var/lib/pacemaker/alert_file.sh 
# pcs alert recipient add alert_file id=my-alert_logfile value=/var/log/pcmk_alert_file.log 
The following example installs the alert_snmp.sh.sample script as alert_snmp.sh and configures an alert that uses the installed alert_snmp.sh alert agent to send cluster events as SNMP traps. By default, the script will send all events except successful monitor calls to the SNMP server. This example configures the timestamp format as a meta option. For information about meta options, see Section 13.1.5, “Alert Meta Options”. After configuring the alert, this example configures a recipient for the alert and displays the alert configuration.
# install --mode=0755 /usr/share/pacemaker/alerts/alert_snmp.sh.sample /var/lib/pacemaker/alert_snmp.sh
# pcs alert create id=snmp_alert path=/var/lib/pacemaker/alert_snmp.sh meta timestamp-format="%Y-%m-%d,%H:%M:%S.%01N"
# pcs alert recipient add snmp_alert value=192.168.1.2
# pcs alert
Alerts:
 Alert: snmp_alert (path=/var/lib/pacemaker/alert_snmp.sh)
  Meta options: timestamp-format=%Y-%m-%d,%H:%M:%S.%01N.
  Recipients:
   Recipient: snmp_alert-recipient (value=192.168.1.2)
The following example installs the alert_smtp.sh agent and then configures an alert that uses the installed alert agent to send cluster events as email messages. After configuring the alert, this example configures a recipient and displays the alert configuration.
# install --mode=0755 /usr/share/pacemaker/alerts/alert_smtp.sh.sample /var/lib/pacemaker/alert_smtp.sh
# pcs alert create id=smtp_alert path=/var/lib/pacemaker/alert_smtp.sh options email_sender=donotreply@example.com
# pcs alert recipient add smtp_alert value=admin@example.com
# pcs alert
Alerts:
 Alert: smtp_alert (path=/var/lib/pacemaker/alert_smtp.sh)
  Options: email_sender=donotreply@example.com
  Recipients:
   Recipient: smtp_alert-recipient (value=admin@example.com)
For more information on the format of the pcs alert create and pcs alert recipient add commands, see Section 13.1.2, “Alert Creation” and Section 13.1.4, “Alert Recipients”.

13.1.2. Alert Creation

The following command creates a cluster alert. The options that you configure are agent-specific configuration values that are passed to the alert agent script at the path you specify as additional environment variables. If you do not specify a value for id, one will be generated. For information on alert meta options, Section 13.1.5, “Alert Meta Options”.
pcs alert create path=path [id=alert-id] [description=description] [options [option=value]...] [meta [meta-option=value]...]
Multiple alert agents may be configured; the cluster will call all of them for each event. Alert agents will be called only on cluster nodes. They will be called for events involving Pacemaker Remote nodes, but they will never be called on those nodes.
The following example creates a simple alert that will call my-script.sh for each event.
# pcs alert create id=my_alert path=/path/to/myscript.sh
For an example that shows how to create a cluster alert that uses one of the sample alert agents, see Section 13.1.1, “Using the Sample Alert Agents”.

13.1.3. Displaying, Modifying, and Removing Alerts

The following command shows all configured alerts along with the values of the configured options.
pcs alert [config|show]
The following command updates an existing alert with the specified alert-id value.
pcs alert update alert-id [path=path] [description=description] [options [option=value]...] [meta [meta-option=value]...]
The following command removes an alert with the specified alert-id value.
pcs alert remove alert-id

13.1.4. Alert Recipients

Usually alerts are directed towards a recipient. Thus each alert may be additionally configured with one or more recipients. The cluster will call the agent separately for each recipient.
The recipient may be anything the alert agent can recognize: an IP address, an email address, a file name, or whatever the particular agent supports.
The following command adds a new recipient to the specified alert.
pcs alert recipient add alert-id value=recipient-value [id=recipient-id] [description=description] [options [option=value]...] [meta [meta-option=value]...]
The following command updates an existing alert recipient.
pcs alert recipient update recipient-id [value=recipient-value] [description=description] [options [option=value]...] [meta [meta-option=value]...]
The following command removes the specified alert recipient.
pcs alert recipient remove recipient-id
The following example command adds the alert recipient my-alert-recipient with a recipient ID of my-recipient-id to the alert my-alert. This will configure the cluster to call the alert script that has been configured for my-alert for each event, passing the recipient some-address as an environment variable.
#  pcs alert recipient add my-alert value=my-alert-recipient id=my-recipient-id options value=some-address

13.1.5. Alert Meta Options

As with resource agents, meta options can be configured for alert agents to affect how Pacemaker calls them. Table 13.1, “Alert Meta Options” describes the alert meta options. Meta options can be configured per alert agent as well as per recipient.

Table 13.1. Alert Meta Options

Meta-AttributeDefaultDescription
timestamp-format
%H:%M:%S.%06N
Format the cluster will use when sending the event’s timestamp to the agent. This is a string as used with the date(1) command.
timeout
30s
If the alert agent does not complete within this amount of time, it will be terminated.
The following example configures an alert that calls the script my-script.sh and then adds two recipients to the alert. The first recipient has an ID of my-alert-recipient1 and the second recipient has an ID of my-alert-recipient2. The script will get called twice for each event, with each call using a 15-second timeout. One call will be passed to the recipient someuser@example.com with a timestamp in the format %D %H:%M, while the other call will be passed to the recipient otheruser@example.com with a timestamp in the format %c. `
# pcs alert create id=my-alert path=/path/to/my-script.sh meta timeout=15s
# pcs alert recipient add my-alert value=someuser@example.com id=my-alert-recipient1 meta timestamp-format=%D %H:%M
# pcs alert recipient add my-alert value=otheruser@example.com id=my-alert-recipient2 meta timestamp-format=%c

13.1.6. Alert Configuration Command Examples

The following sequential examples show some basic alert configuration commands to show the format to use to create alerts, add recipients, and display the configured alerts.
The following commands create a simple alert, add two recipients to the alert, and display the configured values.
  • Since no alert ID value is specified, the system creates an alert ID value of alert.
  • The first recipient creation command specifies a recipient of rec_value. Since this command does not specify a recipient ID, the value of alert-recipient is used as the recipient ID.
  • The second recipient creation command specifies a recipient of rec_value2. This command specifies a recipient ID of my-recipient for the recipient.
# pcs alert create path=/my/path
# pcs alert recipient add alert value=rec_value
# pcs alert recipient add alert value=rec_value2 id=my-recipient
# pcs alert config
Alerts:
 Alert: alert (path=/my/path)
  Recipients:
   Recipient: alert-recipient (value=rec_value)
   Recipient: my-recipient (value=rec_value2)
This following commands add a second alert and a recipient for that alert. The alert ID for the second alert is my-alert and the recipient value is my-other-recipient. Since no recipient ID is specified, the system provides a recipient id of my-alert-recipient.
# pcs alert create id=my-alert path=/path/to/script description=alert_description options option1=value1 opt=val meta meta-option1=2 m=val
# pcs alert recipient add my-alert value=my-other-recipient
# pcs alert
Alerts:
 Alert: alert (path=/my/path)
  Recipients:
   Recipient: alert-recipient (value=rec_value)
   Recipient: my-recipient (value=rec_value2)
 Alert: my-alert (path=/path/to/script)
  Description: alert_description
  Options: opt=val option1=value1
  Meta options: m=val meta-option1=2
  Recipients:
   Recipient: my-alert-recipient (value=my-other-recipient)
The following commands modify the alert values for the alert my-alert and for the recipient my-alert-recipient.
# pcs alert update my-alert options option1=newvalue1 meta m=newval
# pcs alert recipient update my-alert-recipient options option1=new meta metaopt1=newopt
# pcs alert
Alerts:
 Alert: alert (path=/my/path)
  Recipients:
   Recipient: alert-recipient (value=rec_value)
   Recipient: my-recipient (value=rec_value2)
 Alert: my-alert (path=/path/to/script)
  Description: alert_description
  Options: opt=val option1=newvalue1
  Meta options: m=newval meta-option1=2
  Recipients:
   Recipient: my-alert-recipient (value=my-other-recipient)
    Options: option1=new
    Meta options: metaopt1=newopt
The following command removes the recipient my-alert-recipient from alert.
# pcs alert recipient remove my-recipient
# pcs alert
Alerts:
 Alert: alert (path=/my/path)
  Recipients:
   Recipient: alert-recipient (value=rec_value)
 Alert: my-alert (path=/path/to/script)
  Description: alert_description
  Options: opt=val option1=newvalue1
  Meta options: m=newval meta-option1=2
  Recipients:
   Recipient: my-alert-recipient (value=my-other-recipient)
    Options: option1=new
    Meta options: metaopt1=newopt
The following command removes myalert from the configuration.
# pcs alert remove my-alert
# pcs alert
Alerts:
 Alert: alert (path=/my/path)
  Recipients:
   Recipient: alert-recipient (value=rec_value)

13.1.7. Writing an Alert Agent

There are three types of Pacemaker alerts: node alerts, fencing alerts, and resource alerts. The environment variables that are passed to the alert agents can differ, depending on the type of alert. Table 13.2, “Environment Variables Passed to Alert Agents” describes the environment variables that are passed to alert agents and specifies when the environment variable is associated with a specific alert type.

Table 13.2. Environment Variables Passed to Alert Agents

Environment VariableDescription
CRM_alert_kind
The type of alert (node, fencing, or resource)
CRM_alert_version
The version of Pacemaker sending the alert
CRM_alert_recipient
The configured recipient
CRM_alert_node_sequence
A sequence number increased whenever an alert is being issued on the local node, which can be used to reference the order in which alerts have been issued by Pacemaker. An alert for an event that happened later in time reliably has a higher sequence number than alerts for earlier events. Be aware that this number has no cluster-wide meaning.
CRM_alert_timestamp
A timestamp created prior to executing the agent, in the format specified by the timestamp-format meta option. This allows the agent to have a reliable, high-precision time of when the event occurred, regardless of when the agent itself was invoked (which could potentially be delayed due to system load or other circumstances).
CRM_alert_node
Name of affected node
CRM_alert_desc
Detail about event. For node alerts, this is the node’s current state (member or lost). For fencing alerts, this is a summary of the requested fencing operation, including origin, target, and fencing operation error code, if any. For resource alerts, this is a readable string equivalent of CRM_alert_status.
CRM_alert_nodeid
ID of node whose status changed (provided with node alerts only)
CRM_alert_task
The requested fencing or resource operation (provided with fencing and resource alerts only)
CRM_alert_rc
The numerical return code of the fencing or resource operation (provided with fencing and resource alerts only)
CRM_alert_rsc
The name of the affected resource (resource alerts only)
CRM_alert_interval
The interval of the resource operation (resource alerts only)
CRM_alert_target_rc
The expected numerical return code of the operation (resource alerts only)
CRM_alert_status
A numerical code used by Pacemaker to represent the operation result (resource alerts only)
When writing an alert agent, you must take the following concerns into account.
  • Alert agents may be called with no recipient (if none is configured), so the agent must be able to handle this situation, even if it only exits in that case. Users may modify the configuration in stages, and add a recipient later.
  • If more than one recipient is configured for an alert, the alert agent will be called once per recipient. If an agent is not able to run concurrently, it should be configured with only a single recipient. The agent is free, however, to interpret the recipient as a list.
  • When a cluster event occurs, all alerts are fired off at the same time as separate processes. Depending on how many alerts and recipients are configured and on what is done within the alert agents, a significant load burst may occur. The agent could be written to take this into consideration, for example by queueing resource-intensive actions into some other instance, instead of directly executing them.
  • Alert agents are run as the hacluster user, which has a minimal set of permissions. If an agent requires additional privileges, it is recommended to configure sudo to allow the agent to run the necessary commands as another user with the appropriate privileges.
  • Take care to validate and sanitize user-configured parameters, such as CRM_alert_timestamp (whose content is specified by the user-configured timestamp-format), CRM_alert_recipient, and all alert options. This is necessary to protect against configuration errors. In addition, if some user can modify the CIB without having hacluster-level access to the cluster nodes, this is a potential security concern as well, and you should avoid the possibility of code injection.
  • If a cluster contains resources for which the onfail parameter is set to fence, there will be multiple fence notifications on failure, one for each resource for which this parameter is set plus one additional notification. Both the STONITH daemon and the crmd daemon will send notifications. Pacemaker performs only one actual fence operation in this case, however, no matter how many notifications are sent.

Note

The alerts interface is designed to be backward compatible with the external scripts interface used by the ocf:pacemaker:ClusterMon resource. To preserve this compatibility, the environment variables passed to alert agents are available prepended with CRM_notify_ as well as CRM_alert_. One break in compatibility is that the ClusterMon resource ran external scripts as the root user, while alert agents are run as the hacluster user. For information on configuring scripts that are triggered by the ClusterMon, see Section 13.2, “Event Notification with Monitoring Resources”.

13.2. Event Notification with Monitoring Resources

The ocf:pacemaker:ClusterMon resource can monitor the cluster status and trigger alerts on each cluster event. This resource runs the crm_mon command in the background at regular intervals.
By default, the crm_mon command listens for resource events only; to enable listing for fencing events you can provide the --watch-fencing option to the command when you configure the ClusterMon resource. The crm_mon command does not monitor for membership issues but will print a message when fencing is started and when monitoring is started for that node, which would imply that a member just joined the cluster.
The ClusterMon resource can execute an external program to determine what to do with cluster notifications by means of the extra_options parameter. Table 13.3, “Environment Variables Passed to the External Monitor Program” lists the environment variables that are passed to that program, which describe the type of cluster event that occurred.

Table 13.3. Environment Variables Passed to the External Monitor Program

Environment VariableDescription
CRM_notify_recipient
The static external-recipient from the resource definition
CRM_notify_node
The node on which the status change happened
CRM_notify_rsc
The name of the resource that changed the status
CRM_notify_task
The operation that caused the status change
CRM_notify_desc
The textual output relevant error code of the operation (if any) that caused the status change
CRM_notify_rc
The return code of the operation
CRM_target_rc
The expected return code of the operation
CRM_notify_status
The numerical representation of the status of the operation
The following example configures a ClusterMon resource that executes the external program crm_logger.sh which will log the event notifications specified in the program.
The following procedure creates the crm_logger.sh program that this resource will use.
  1. On one node of the cluster, create the program that will log the event notifications.
    # cat <<-END >/usr/local/bin/crm_logger.sh
    #!/bin/sh
    logger -t "ClusterMon-External" "${CRM_notify_node} ${CRM_notify_rsc} \
    ${CRM_notify_task} ${CRM_notify_desc} ${CRM_notify_rc} \
    ${CRM_notify_target_rc} ${CRM_notify_status} ${CRM_notify_recipient}";
    exit;
    END
  2. Set the ownership and permissions for the program.
    # chmod 700 /usr/local/bin/crm_logger.sh
    # chown root.root /usr/local/bin/crm_logger.sh
  3. Use the scp command to copy the crm_logger.sh program to the other nodes of the cluster, putting the program in the same location on those nodes and setting the same ownership and permissions for the program.
The following example configures the ClusterMon resource, named ClusterMon-External, that runs the program /usr/local/bin/crm_logger.sh. The ClusterMon resource outputs the cluster status to an html file, which is /var/www/html/cluster_mon.html in this example. The pidfile detects whether ClusterMon is already running; in this example that file is /var/run/crm_mon-external.pid. This resource is created as a clone so that it will run on every node in the cluster. The watch-fencing is specified to enable monitoring of fencing events in addition to resource events, including the start/stop/monitor, start/monitor. and stop of the fencing resource.
# pcs resource create ClusterMon-External ClusterMon user=root \
update=10 extra_options="-E /usr/local/bin/crm_logger.sh --watch-fencing" \
htmlfile=/var/www/html/cluster_mon.html \
pidfile=/var/run/crm_mon-external.pid clone

Note

The crm_mon command that this resource executes and which could be run manually is as follows:
# /usr/sbin/crm_mon -p /var/run/crm_mon-manual.pid -d -i 5 \
-h /var/www/html/crm_mon-manual.html -E "/usr/local/bin/crm_logger.sh" \
--watch-fencing
The following example shows the format of the output of the monitoring notifications that this example yields.
Aug  7 11:31:32 rh6node1pcmk ClusterMon-External: rh6node2pcmk.examplerh.com ClusterIP st_notify_fence Operation st_notify_fence requested by rh6node1pcmk.examplerh.com for peer rh6node2pcmk.examplerh.com: OK (ref=b206b618-e532-42a5-92eb-44d363ac848e) 0 0 0 #177
Aug  7 11:31:32 rh6node1pcmk ClusterMon-External: rh6node1pcmk.examplerh.com ClusterIP start OK 0 0 0
Aug  7 11:31:32 rh6node1pcmk ClusterMon-External: rh6node1pcmk.examplerh.com ClusterIP monitor OK 0 0 0
Aug  7 11:33:59 rh6node1pcmk ClusterMon-External: rh6node1pcmk.examplerh.com fence_xvms monitor OK 0 0 0
Aug  7 11:33:59 rh6node1pcmk ClusterMon-External: rh6node1pcmk.examplerh.com ClusterIP monitor OK 0 0 0
Aug  7 11:33:59 rh6node1pcmk ClusterMon-External: rh6node1pcmk.examplerh.com ClusterMon-External start OK 0 0 0
Aug  7 11:33:59 rh6node1pcmk ClusterMon-External: rh6node1pcmk.examplerh.com fence_xvms start OK 0 0 0
Aug  7 11:33:59 rh6node1pcmk ClusterMon-External: rh6node1pcmk.examplerh.com ClusterIP start OK 0 0 0
Aug  7 11:33:59 rh6node1pcmk ClusterMon-External: rh6node1pcmk.examplerh.com ClusterMon-External monitor OK 0 0 0
Aug  7 11:34:00 rh6node1pcmk crmd[2887]:   notice: te_rsc_command: Initiating action 8: monitor ClusterMon-External:1_monitor_0 on rh6node2pcmk.examplerh.com
Aug  7 11:34:00 rh6node1pcmk crmd[2887]:   notice: te_rsc_command: Initiating action 16: start ClusterMon-External:1_start_0 on rh6node2pcmk.examplerh.com
Aug  7 11:34:00 rh6node1pcmk ClusterMon-External: rh6node1pcmk.examplerh.com ClusterIP stop OK 0 0 0
Aug  7 11:34:00 rh6node1pcmk crmd[2887]:   notice: te_rsc_command: Initiating action 15: monitor ClusterMon-External_monitor_10000 on rh6node2pcmk.examplerh.com
Aug  7 11:34:00 rh6node1pcmk ClusterMon-External: rh6node2pcmk.examplerh.com ClusterMon-External start OK 0 0 0
Aug  7 11:34:00 rh6node1pcmk ClusterMon-External: rh6node2pcmk.examplerh.com ClusterMon-External monitor OK 0 0 0
Aug  7 11:34:00 rh6node1pcmk ClusterMon-External: rh6node2pcmk.examplerh.com ClusterIP start OK 0 0 0
Aug  7 11:34:00 rh6node1pcmk ClusterMon-External: rh6node2pcmk.examplerh.com ClusterIP monitor OK 0 0 0

Chapter 14. Configuring Multi-Site Clusters with Pacemaker

When a cluster spans more than one site, issues with network connectivity between the sites can lead to split-brain situations. When connectivity drops, there is no way for a node on one site to determine whether a node on another site has failed or is still functioning with a failed site interlink. In addition, it can be problematic to provide high availability services across two sites which are too far apart to keep synchronous.
To address these issues, Red Hat Enterprise Linux release 7.4 provides full support for the ability to configure high availability clusters that span multiple sites through the use of a Booth cluster ticket manager. The Booth ticket manager is a distributed service that is meant to be run on a different physical network than the networks that connect the cluster nodes at particular sites. It yields another, loose cluster, a Booth formation, that sits on top of the regular clusters at the sites. This aggregated communication layer facilitates consensus-based decision processes for individual Booth tickets.
A Booth ticket is a singleton in the Booth formation and represents a time-sensitive, movable unit of authorization. Resources can be configured to require a certain ticket to run. This can ensure that resources are run at only one site at a time, for which a ticket or tickets have been granted.
You can think of a Booth formation as an overlay cluster consisting of clusters running at different sites, where all the original clusters are independent of each other. It is the Booth service which communicates to the clusters whether they have been granted a ticket, and it is Pacemaker that determines. whether to run resources in a cluster based on a Pacemaker ticket constraint. This means that when using the ticket manager, each of the clusters can run its own resources as well as shared resources. For example there can be resources A, B and C running only in one cluster, resources D, E, and F running only in the other cluster, and resources G and H running in either of the two clusters as determined by a ticket. It is also possible to have an additional resource J that could run in either of the two clusters as determined by a separate ticket.
The following procedure provides an outline of the steps you follow to configure a multi-site configuration that uses the Booth ticket manager.
These example commands use the following arrangement:
  • Cluster 1 consists of the nodes cluster1-node1 and cluster1-node2
  • Cluster 1 has a floating IP address assigned to it of 192.168.11.100
  • Cluster 2 consists of cluster2-node1 and cluster2-node2
  • Cluster 2 has a floating IP address assigned to it of 192.168.22.100
  • The arbitrator node is arbitrator-node with an ip address of 192.168.99.100
  • The name of the Booth ticket that this configuration uses is apacheticket
These example commands assume that the cluster resources for an Apache service have been configured as part of the resource group apachegroup for each cluster. It is not required that the resources and resource groups be the same on each cluster to configure a ticket constraint for those resources, since the Pacemaker instance for each cluster is independent, but that is a common failover scenario.
For a full cluster configuration procedure that configures an Apache service in a cluster, see the example in High Availability Add-On Administration.
Note that at any time in the configuration procedure you can enter the pcs booth config command to display the booth configuration for the current node or cluster or the pcs booth status command to display the current status of booth on the local node.
  1. Install the booth-site Booth ticket manager package on each node of both clusters.
    [root@cluster1-node1 ~]# yum install -y booth-site
    [root@cluster1-node2 ~]# yum install -y booth-site
    [root@cluster2-node1 ~]# yum install -y booth-site
    [root@cluster2-node2 ~]# yum install -y booth-site
  2. Install the pcs, booth-core, and booth-arbitrator packages on the arbitrator node.
    [root@arbitrator-node ~]# yum install -y pcs booth-core booth-arbitrator
  3. Ensure that ports 9929/tcp and 9929/udp are open on all cluster nodes and on the arbitrator node. To do this:
    • Run the following commands on all nodes in both clusters.
    • In addition, enter the following commands on the arbitrator node.
    # firewall-cmd --add-port=9929/udp
    # firewall-cmd --add-port=9929/tcp
    # firewall-cmd --add-port=9929/udp --permanent
    # firewall-cmd --add-port=9929/tcp --permanent
  4. Create a Booth configuration on one node of one cluster. The addresses you specify for each cluster and for the arbitrator must be IP addresses. For each cluster, you specify a floating IP address.
    [cluster1-node1 ~] # pcs booth setup sites 192.168.11.100 192.168.22.100 arbitrators 192.168.99.100
    This command creates the configuration files /etc/booth/booth.conf and /etc/booth/booth.key on the node from which it is run.
  5. Create a ticket for the Booth configuration. This is the ticket that you will use to define the resource constraint that will allow resources to run only when this ticket has been granted to the cluster.
    This basic failover configuration procedure uses only one ticket, but you can create additional tickets for more complicated scenarios where each ticket is associated with a different resource or resources.
    [cluster1-node1 ~] # pcs booth ticket add apacheticket
  6. Synchronize the Booth configuration to all nodes in the current cluster.
    [cluster1-node1 ~] # pcs booth sync
  7. From the arbitrator node, pull the Booth configuration to the arbitrator. If you have not previously done so, you must first authenticate pcs to the node from which you are pulling the configuration.
    [arbitrator-node ~] # pcs cluster auth cluster1-node1
    [arbitrator-node ~] # pcs booth pull cluster1-node1
  8. Pull the Booth configuration to the other cluster and synchronize to all the nodes of that cluster. As with the arbitrator node, if you have not previously done so, you must first authenticate pcs to the node from which you are pulling the configuration.
    [cluster2-node1 ~] # pcs cluster auth cluster1-node1
    [cluster2-node1 ~] # pcs booth pull cluster1-node1
    [cluster2-node1 ~] # pcs booth sync
  9. Start and enable Booth on the arbitrator.

    Note

    You must not manually start or enable Booth on any of the nodes of the clusters since Booth runs as a Pacemaker resource in those clusters.
    [arbitrator-node ~] # pcs booth start
    [arbitrator-node ~] # pcs booth enable
  10. Configure Booth to run as a cluster resource on both cluster sites. This creates a resource group with booth-ip and booth-service as members of that group.
    [cluster1-node1 ~] # pcs booth create ip 192.168.11.100
    [cluster2-node1 ~] # pcs booth create ip 192.168.22.100
  11. Add a ticket constraint to the resource group you have defined for each cluster.
    [cluster1-node1 ~] # pcs constraint ticket add apacheticket apachegroup
    [cluster2-node1 ~] # pcs constraint ticket add apacheticket apachegroup
    You can enter the following command to display the currently configured ticket constraints.
    pcs constraint ticket [show]
    
  12. Grant the ticket you created for this setup to the first cluster.
    Note that it is not necessary to have defined ticket constraints before granting a ticket. Once you have initially granted a ticket to a cluster, then Booth takes over ticket management unless you override this manually with the pcs booth ticket revoke command. For information on the pcs booth administration commands, see the PCS help screen for the pcs booth command.
    [cluster1-node1 ~] # pcs booth ticket grant apacheticket
It is possible to add or remove tickets at any time, even after completing this procedure. After adding or removing a ticket, however, you must synchronize the configuration files to the other nodes and clusters as well as to the arbitrator and grant the ticket as is shown in this procedure.
For information on additional Booth administration commands that you can use for cleaning up and removing Booth configuration files, tickets, and resources, see the PCS help screen for the pcs booth command.

Appendix A. OCF Return Codes

This appendix describes the OCF return codes and how they are interpreted by Pacemaker.
The first thing the cluster does when an agent returns a code is to check the return code against the expected result. If the result does not match the expected value, then the operation is considered to have failed, and recovery action is initiated.
For any invocation, resource agents must exit with a defined return code that informs the caller of the outcome of the invoked action.
There are three types of failure recovery, as described in Table A.1, “Types of Recovery Performed by the Cluster”.

Table A.1. Types of Recovery Performed by the Cluster

TypeDescriptionAction Taken by the Cluster
soft
A transient error occurred.
Restart the resource or move it to a new location .
hard
A non-transient error that may be specific to the current node occurred.
Move the resource elsewhere and prevent it from being retried on the current node.
fatal
A non-transient error that will be common to all cluster nodes occurred (for example, a bad configuration was specified).
Stop the resource and prevent it from being started on any cluster node.
Table A.2, “OCF Return Codes” provides The OCF return codes and the type of recovery the cluster will initiate when a failure code is received. Note that even actions that return 0 (OCF alias OCF_SUCCESS) can be considered to have failed, if 0 was not the expected return value.

Table A.2. OCF Return Codes

Return CodeOCF LabelDescription
0
OCF_SUCCESS
The action completed successfully. This is the expected return code for any successful start, stop, promote, and demote command.
Type if unexpected: soft
1
OCF_ERR_GENERIC
The action returned a generic error.
Type: soft
The resource manager will attempt to recover the resource or move it to a new location.
2
OCF_ERR_ARGS
The resource’s configuration is not valid on this machine. For example, it refers to a location not found on the node.
Type: hard
The resource manager will move the resource elsewhere and prevent it from being retried on the current node
3
OCF_ERR_UNIMPLEMENTED
The requested action is not implemented.
Type: hard
4
OCF_ERR_PERM
The resource agent does not have sufficient privileges to complete the task. This may be due, for example, to the agent not being able to open a certain file, to listen on a specific socket, or to write to a directory.
Type: hard
Unless specifically configured otherwise, the resource manager will attempt to recover a resource which failed with this error by restarting the resource on a different node (where the permission problem may not exist).
5
OCF_ERR_INSTALLED
A required component is missing on the node where the action was executed. This may be due to a required binary not being executable, or a vital configuration file being unreadable.
Type: hard
Unless specifically configured otherwise, the resource manager will attempt to recover a resource which failed with this error by restarting the resource on a different node (where the required files or binaries may be present).
6
OCF_ERR_CONFIGURED
The resource’s configuration on the local node is invalid.
Type: fatal
When this code is returned, Pacemaker will prevent the resource from running on any node in the cluster, even if the service configuraiton is valid on some other node.
7
OCF_NOT_RUNNING
The resource is safely stopped. This implies that the resource has either gracefully shut down, or has never been started.
Type if unexpected: soft
The cluster will not attempt to stop a resource that returns this for any action.
8
OCF_RUNNING_MASTER
The resource is running in master mode.
Type if unexpected: soft
9
OCF_FAILED_MASTER
The resource is in master mode but has failed.
Type: soft
The resource will be demoted, stopped and then started (and possibly promoted) again.
other
N/A
Custom error code.

Appendix B. Cluster Creation in Red Hat Enterprise Linux 6 and Red Hat Enterprise Linux 7

Configuring a Red Hat High Availability Cluster in Red Hat Enterprise Linux 7 with Pacemaker requires a different set of configuration tools with a different administrative interface than configuring a cluster in Red Hat Enterprise Linux 6 with rgmanager. Section B.1, “Cluster Creation with rgmanager and with Pacemaker” summarizes the configuration differences between the various cluster components.
Red Hat Enterprise Linux 6.5 and later releases support cluster configuration with Pacemaker, using the pcs configuration tool. Section B.2, “Pacemaker Installation in Red Hat Enterprise Linux 6 and Red Hat Enterprise Linux 7” summarizes the Pacemaker installation differences between Red Hat Enterprise Linux 6 and Red Hat Enterprise Linux 7.

B.1. Cluster Creation with rgmanager and with Pacemaker

Table B.1, “Comparison of Cluster Configuration with rgmanager and with Pacemaker” provides a comparative summary of how you configure the components of a cluster with rgmanager in Red Hat Enterprise Linux 6 and with Pacemaker in Red Hat Enterprise Linux 7.

Table B.1. Comparison of Cluster Configuration with rgmanager and with Pacemaker

Configuration ComponentrgmanagerPacemaker
Cluster configuration file
The cluster configuration file on each node is cluster.conf file, which can can be edited directly. Otherwise, use the luci or ccs interface to define the cluster configuration.
The cluster and Pacemaker configuration files are corosync.conf and cib.xml. Do not edit the cib.xml file directly; use the pcs or pcsd interface instead.
Network setup
Configure IP addresses and SSH before configuring the cluster.
Configure IP addresses and SSH before configuring the cluster.
Cluster Configuration Tools
luci, ccs command, manual editing of cluster.conf file.
pcs or pcsd.
Installation
Install rgmanager (which pulls in all dependencies, including ricci, luci, and the resource and fencing agents). If needed, install lvm2-cluster and gfs2-utils.
Install pcs, and the fencing agents you require. If needed, install lvm2-cluster and gfs2-utils.
Starting cluster services
Start and enable cluster services with the following procedure:
  1. Start rgmanager, cman, and, if needed, clvmd and gfs2.
  2. Start ricci, and start luci if using the luci interface.
  3. Run chkconfig on for the needed services so that they start at each runtime.
Alternately, you can enter ccs --start to start and enable the cluster services.
Start and enable cluster services with the following procedure:
  1. On every node, execute systemctl start pcsd.service, then systemctl enable pcsd.service to enable pcsd to start at runtime.
  2. On one node in the cluster, enter pcs cluster start --all to start corosync and pacemaker.
Controlling access to configuration tools
For luci, the root user or a user with luci permissions can access luci. All access requires the ricci password for the node.
The pcsd gui requires that you authenticate as user hacluster, which is the common system user. The root user can set the password for hacluster.
Cluster creation
Name the cluster and define which nodes to include in the cluster with luci or ccs, or directly edit the cluster.conf file.
Name the cluster and include nodes with pcs cluster setup command or with the pcsd Web UI. You can add nodes to an existing cluster with the pcs cluster node add command or with the pcsd Web UI.
Propagating cluster configuration to all nodes
When configuration a cluster with luci, propagation is automatic. With ccs, use the --sync option. You can also use the cman_tool version -r command.
Propagation of the cluster and Pacemaker configuration files, corosync.conf and cib.xml, is automatic on cluster setup or when adding a node or resource.
Global cluster properties
The following feature are supported with rgmanager in Red Hat Enterprise Linux 6:
* You can configure the system so that the system chooses which multicast address to use for IP multicasting in the cluster network.
* If IP multicasting is not available, you can use UDP Unicast transport mechanism.
* You can configure a cluster to use RRP protocol.
Pacemaker in Red Hat Enterprise Linux 7 supports the following features for a cluster:
* You can set no-quorum-policy for the cluster to specify what the system should do when the cluster does not have quorum.
* For additional cluster properties you can set, see Table 12.1, “Cluster Properties”.
Logging
You can set global and daemon-specific logging configuration.
See the file /etc/sysconfig/pacemaker for information on how to configure logging manually.
Validating the cluster
Cluster validation is automatic with luci and with ccs, using the cluster schema. The cluster is automatically validated on startup.
The cluster is automatically validated on startup, or you can validate the cluster with pcs cluster verify.
Quorum in two-node clusters
With a two-node cluster, you can configure how the system determines quorum:
* Configure a quorum disk
* Use ccs or edit the cluster.conf file to set two_node=1 and expected_votes=1 to allow a single node to maintain quorum.
pcs automatically adds the necessary options for a two-node cluster to corosync.
Cluster status
On luci, the current status of the cluster is visible in the various components of the interface, which can be refreshed. You can use the --getconf option of the ccs command to see current the configuration file. You can use the clustat command to display cluster status.
You can display the current cluster status with the pcs status command.
Resources
You add resources of defined types and configure resource-specific properties with luci or the ccs command, or by editing the cluster.conf configuration file.
You add resources of defined types and configure resource-specific properties with the pcs resource create command or with the pcsd Web UI. For general information on configuring cluster resources with Pacemaker see Chapter 6, Configuring Cluster Resources.
Resource behavior, grouping, and start/stop order
Define cluster services to configure how resources interact.
With Pacemaker, you use resource groups as a shorthand method of defining a set of resources that need to be located together and started and stopped sequentially. In addition, you define how resources behave and interact in the following ways:
* You set some aspects of resource behavior as resource options.
* You use location constraints to determine which nodes a resource can run on.
* You use order constraints to determine the order in which resources run.
* You use colocation constraints to determine that the location of one resource depends on the location of another resource.
For more complete information on these topics, see Chapter 6, Configuring Cluster Resources and Chapter 7, Resource Constraints.
Resource administration: Moving, starting, stopping resources
With luci, you can manage clusters, individual cluster nodes, and cluster services. With the ccs command, you can manage cluster. You can use the clusvadm to manage cluster services.
You can temporarily disable a node so that it cannot host resources with the pcs cluster standby command, which causes the resources to migrate. You can stop a resource with the pcs resource disable command.
Removing a cluster configuration completely
With luci, you can select all nodes in a cluster for deletion to delete a cluster entirely. You can also remove the cluster.conf from each node in the cluster.
You can remove a cluster configuration with the pcs cluster destroy command.
Resources active on multiple nodes, resources active on multiple nodes in multiple modes
No equivalent.
With Pacemaker, you can clone resources so that they can run in multiple nodes, and you can define cloned resources as master and slave resources so that they can run in multiple modes. For information on cloned resources and master/slave resources, see Chapter 9, Advanced Configuration.
Fencing -- single fence device per node
Create fencing devices globally or locally and add them to nodes. You can define post-fail delay and post-join delay values for the cluster as a whole.
Create a fencing device for each node with the pcs stonith create command or with the pcsd Web UI. For devices that can fence multiple nodes, you need to define them only once rather than separately for each node. You can also define pcmk_host_map to configure fencing devices for all nodes with a single command; for information on pcmk_host_map see Table 5.1, “General Properties of Fencing Devices”. You can define the stonith-timeout value for the cluster as a whole.
Multiple (backup) fencing devices per node
Define backup devices with luci or the ccs command, or by editing the cluster.conf file directly.
Configure fencing levels.

B.2. Pacemaker Installation in Red Hat Enterprise Linux 6 and Red Hat Enterprise Linux 7

Red Hat Enterprise Linux 6.5 and later releases support cluster configuration with Pacemaker, using the pcs configuration tool. There are, however, some differences in cluster installation between Red Hat Enterprise Linux 6 and Red Hat Enterprise Linux 7 when using Pacemaker.
The following commands install the Red Hat High Availability Add-On software packages that Pacemaker requires in Red Hat Enterprise Linux 6 and prevent corosync from starting without cman. You must enter these commands on each node in the cluster.
[root@rhel6]# yum install pacemaker cman pcs
[root@rhel6]# chkconfig corosync off
[root@rhel6]# chkconfig cman off
On each node in the cluster, you set up a password for the pcs administration account named hacluster, and you start and enable the pcsd service.
[root@rhel6]# passwd hacluster
[root@rhel6]# service pcsd start
[root@rhel6]# chkconfig pcsd on
On one node in the cluster, you then authenticate the administration account for the nodes of the cluster.
[root@rhel6]# pcs cluster auth [node] [...] [-u username] [-p password]
In Red Hat Enterprise Linux 7, you run the following commands on each node in the cluster to install the Red Hat High Availability Add-On software packages that Pacemaker requires, set up a password for the pcs administration account named hacluster, and start and enable the pcsd service,
[root@rhel7]# yum install pcs pacemaker fence-agents-all
[root@rhel7]# passwd hacluster
[root@rhel7]# systemctl start pcsd.service
[root@rhel7]# systemctl enable pcsd.service
In Red Hat Enterprise Linux 7, as in Red Hat Enterprise Linux 6, you authenticate the administration account for the nodes of the cluster by running the following command on one node in the cluster.
[root@rhel7]# pcs cluster auth [node] [...] [-u username] [-p password]

Appendix C. Revision History

Revision History
Revision 6.1-1Thu Oct 4 2018Steven Levine
Document version for 7.6 GA publication.
Revision 5.1-2Thu Mar 15 2018Steven Levine
Document version for 7.5 GA publication.
Revision 5.1-0Thu Dec 14 2017Steven Levine
Document version for 7.5 Beta publication.
Revision 4.1-9Tue Oct 17 2017Steven Levine
Updated version for 7.4.
Revision 4.1-5Wed Jul 19 2017Steven Levine
Document version for 7.4 GA publication.
Revision 4.1-2Wed May 10 2017Steven Levine
Preparing document for 7.4 Beta publication.
Revision 3.1-10Tue May 2 2017Steven Levine
Update to version for 7.3 GA publication.
Revision 3.1-4Mon Oct 17 2016Steven Levine
Version for 7.3 GA publication.
Revision 3.1-3Wed Aug 17 2016Steven Levine
Preparing document for 7.3 Beta publication.
Revision 2.1-8Mon Nov 9 2015Steven Levine
Preparing document for 7.2 GA publication
Revision 2.1-5Mon Aug 24 2015Steven Levine
Preparing document for 7.2 Beta publication.
Revision 1.1-9Mon Feb 23 2015Steven Levine
Version for 7.1 GA release
Revision 1.1-7Thu Dec 11 2014Steven Levine
Version for 7.1 Beta release
Revision 0.1-41Mon Jun 2 2014Steven Levine
Version for 7.0 GA release
Revision 0.1-2Thu May 16 2013Steven Levine
First printing of initial draft

Index

C

Clone
Option
clone-max, Creating and Removing a Cloned Resource
clone-node-max, Creating and Removing a Cloned Resource
globally-unique, Creating and Removing a Cloned Resource
interleave, Creating and Removing a Cloned Resource
notify, Creating and Removing a Cloned Resource
ordered, Creating and Removing a Cloned Resource
Clone Option, Creating and Removing a Cloned Resource
Clone Resources, Resource Clones
clone-max, Creating and Removing a Cloned Resource
Clone Option, Creating and Removing a Cloned Resource
clone-node-max, Creating and Removing a Cloned Resource
Clone Option, Creating and Removing a Cloned Resource
Clones, Resource Clones
Cluster
Option
batch-limit, Summary of Cluster Properties and Options
cluster-delay, Summary of Cluster Properties and Options
cluster-infrastructure, Summary of Cluster Properties and Options
cluster-recheck-interval, Summary of Cluster Properties and Options
dc-version, Summary of Cluster Properties and Options
enable-acl, Summary of Cluster Properties and Options
last-lrm-refresh, Summary of Cluster Properties and Options
maintenance-mode, Summary of Cluster Properties and Options
migration-limit, Summary of Cluster Properties and Options
no-quorum-policy, Summary of Cluster Properties and Options
pe-error-series-max, Summary of Cluster Properties and Options
pe-input-series-max, Summary of Cluster Properties and Options
pe-warn-series-max, Summary of Cluster Properties and Options
placement-strategy, Summary of Cluster Properties and Options
shutdown-escalation, Summary of Cluster Properties and Options
start-failure-is-fatal, Summary of Cluster Properties and Options
stonith-action, Summary of Cluster Properties and Options
stonith-enabled, Summary of Cluster Properties and Options
stonith-timeout, Summary of Cluster Properties and Options
stop-all-resources, Summary of Cluster Properties and Options
stop-orphan-actions, Summary of Cluster Properties and Options
stop-orphan-resources, Summary of Cluster Properties and Options
symmetric-cluster, Summary of Cluster Properties and Options
Querying Properties, Querying Cluster Property Settings
Removing Properties, Setting and Removing Cluster Properties
Setting Properties, Setting and Removing Cluster Properties
cluster administration
configuring ACPI, Configuring ACPI For Use with Integrated Fence Devices
Cluster Option, Summary of Cluster Properties and Options
Cluster Properties, Setting and Removing Cluster Properties, Querying Cluster Property Settings
cluster status
display, Displaying Cluster Status
cluster-delay, Summary of Cluster Properties and Options
Cluster Option, Summary of Cluster Properties and Options
cluster-infrastructure, Summary of Cluster Properties and Options
Cluster Option, Summary of Cluster Properties and Options
cluster-recheck-interval, Summary of Cluster Properties and Options
Cluster Option, Summary of Cluster Properties and Options
Colocation, Colocation of Resources
Constraint
Attribute Expression, Node Attribute Expressions
attribute, Node Attribute Expressions
operation, Node Attribute Expressions
type, Node Attribute Expressions
value, Node Attribute Expressions
Date Specification, Date Specifications
hours, Date Specifications
id, Date Specifications
monthdays, Date Specifications
months, Date Specifications
moon, Date Specifications
weekdays, Date Specifications
weeks, Date Specifications
weekyears, Date Specifications
yeardays, Date Specifications
years, Date Specifications
Date/Time Expression, Time/Date Based Expressions
end, Time/Date Based Expressions
operation, Time/Date Based Expressions
start, Time/Date Based Expressions
Duration, Durations
Rule, Pacemaker Rules
boolean-op, Pacemaker Rules
role, Pacemaker Rules
score, Pacemaker Rules
score-attribute, Pacemaker Rules
Constraint Expression, Node Attribute Expressions, Time/Date Based Expressions
Constraint Rule, Pacemaker Rules
Constraints
Colocation, Colocation of Resources
Location
id, Basic Location Constraints
score, Basic Location Constraints
Order, Order Constraints
kind, Order Constraints

F

failure-timeout, Resource Meta Options
Resource Option, Resource Meta Options
features, new and changed, New and Changed Features

K

kind, Order Constraints
Order Constraints, Order Constraints

M

maintenance-mode, Summary of Cluster Properties and Options
Cluster Option, Summary of Cluster Properties and Options
master-max, Multistate Resources: Resources That Have Multiple Modes
Multi-State Option, Multistate Resources: Resources That Have Multiple Modes
master-node-max, Multistate Resources: Resources That Have Multiple Modes
Multi-State Option, Multistate Resources: Resources That Have Multiple Modes
migration-limit, Summary of Cluster Properties and Options
Cluster Option, Summary of Cluster Properties and Options
migration-threshold, Resource Meta Options
Resource Option, Resource Meta Options
monthdays, Date Specifications
Date Specification, Date Specifications
months, Date Specifications
Date Specification, Date Specifications
moon, Date Specifications
Date Specification, Date Specifications
Moving, Manually Moving Resources Around the Cluster
Resources, Manually Moving Resources Around the Cluster
Multi-State
Option
master-max, Multistate Resources: Resources That Have Multiple Modes
master-node-max, Multistate Resources: Resources That Have Multiple Modes
Property
id, Multistate Resources: Resources That Have Multiple Modes
Multi-State Option, Multistate Resources: Resources That Have Multiple Modes
Multi-State Property, Multistate Resources: Resources That Have Multiple Modes
multiple-active, Resource Meta Options
Resource Option, Resource Meta Options
multiplier, Moving Resources Due to Connectivity Changes
Ping Resource Option, Moving Resources Due to Connectivity Changes
Multistate, Multistate Resources: Resources That Have Multiple Modes, Multistate Stickiness

O

OCF
return codes, OCF Return Codes
on-fail, Resource Operations
Action Property, Resource Operations
operation, Node Attribute Expressions, Time/Date Based Expressions
Constraint Expression, Node Attribute Expressions, Time/Date Based Expressions
Option
batch-limit, Summary of Cluster Properties and Options
clone-max, Creating and Removing a Cloned Resource
clone-node-max, Creating and Removing a Cloned Resource
cluster-delay, Summary of Cluster Properties and Options
cluster-infrastructure, Summary of Cluster Properties and Options
cluster-recheck-interval, Summary of Cluster Properties and Options
dampen, Moving Resources Due to Connectivity Changes
dc-version, Summary of Cluster Properties and Options
enable-acl, Summary of Cluster Properties and Options
failure-timeout, Resource Meta Options
globally-unique, Creating and Removing a Cloned Resource
host_list, Moving Resources Due to Connectivity Changes
interleave, Creating and Removing a Cloned Resource
is-managed, Resource Meta Options
last-lrm-refresh, Summary of Cluster Properties and Options
maintenance-mode, Summary of Cluster Properties and Options
master-max, Multistate Resources: Resources That Have Multiple Modes
master-node-max, Multistate Resources: Resources That Have Multiple Modes
migration-limit, Summary of Cluster Properties and Options
migration-threshold, Resource Meta Options
multiple-active, Resource Meta Options
multiplier, Moving Resources Due to Connectivity Changes
no-quorum-policy, Summary of Cluster Properties and Options
notify, Creating and Removing a Cloned Resource
ordered, Creating and Removing a Cloned Resource
pe-error-series-max, Summary of Cluster Properties and Options
pe-input-series-max, Summary of Cluster Properties and Options
pe-warn-series-max, Summary of Cluster Properties and Options
placement-strategy, Summary of Cluster Properties and Options
priority, Resource Meta Options
requires, Resource Meta Options
resource-stickiness, Resource Meta Options
shutdown-escalation, Summary of Cluster Properties and Options
start-failure-is-fatal, Summary of Cluster Properties and Options
stonith-action, Summary of Cluster Properties and Options
stonith-enabled, Summary of Cluster Properties and Options
stonith-timeout, Summary of Cluster Properties and Options
stop-all-resources, Summary of Cluster Properties and Options
stop-orphan-actions, Summary of Cluster Properties and Options
stop-orphan-resources, Summary of Cluster Properties and Options
symmetric-cluster, Summary of Cluster Properties and Options
target-role, Resource Meta Options
Order
kind, Order Constraints
Order Constraints, Order Constraints
symmetrical, Order Constraints
ordered, Creating and Removing a Cloned Resource
Clone Option, Creating and Removing a Cloned Resource
Ordering, Order Constraints
overview
features, new and changed, New and Changed Features

Q

Querying
Cluster Properties, Querying Cluster Property Settings
Querying Options, Querying Cluster Property Settings

R

Removing
Cluster Properties, Setting and Removing Cluster Properties
Removing Properties, Setting and Removing Cluster Properties
requires, Resource Meta Options
Resource, Resource Properties
Constraint
Attribute Expression, Node Attribute Expressions
Date Specification, Date Specifications
Date/Time Expression, Time/Date Based Expressions
Duration, Durations
Rule, Pacemaker Rules
Constraints
Colocation, Colocation of Resources
Order, Order Constraints
Location
Determine by Rules, Using Rules to Determine Resource Location
Location Relative to other Resources, Colocation of Resources
Moving, Manually Moving Resources Around the Cluster
Option
failure-timeout, Resource Meta Options
is-managed, Resource Meta Options
migration-threshold, Resource Meta Options
multiple-active, Resource Meta Options
priority, Resource Meta Options
requires, Resource Meta Options
resource-stickiness, Resource Meta Options
target-role, Resource Meta Options
Property
id, Resource Properties
provider, Resource Properties
standard, Resource Properties
type, Resource Properties
Start Order, Order Constraints
Resource Option, Resource Meta Options
resource-stickiness, Resource Meta Options
Groups, Group Stickiness
Multi-State, Multistate Stickiness
Resource Option, Resource Meta Options
Resources, Manually Moving Resources Around the Cluster
Clones, Resource Clones
Groups, Resource Groups
Multistate, Multistate Resources: Resources That Have Multiple Modes
resources
cleanup, Cluster Resources Cleanup
disabling, Enabling and Disabling Cluster Resources
enabling, Enabling and Disabling Cluster Resources
role, Pacemaker Rules
Constraint Rule, Pacemaker Rules
Rule, Pacemaker Rules
boolean-op, Pacemaker Rules
Determine Resource Location, Using Rules to Determine Resource Location
role, Pacemaker Rules
score, Pacemaker Rules
score-attribute, Pacemaker Rules

S

score, Basic Location Constraints, Pacemaker Rules
Constraint Rule, Pacemaker Rules
Location Constraints, Basic Location Constraints
score-attribute, Pacemaker Rules
Constraint Rule, Pacemaker Rules
Setting
Cluster Properties, Setting and Removing Cluster Properties
Setting Properties, Setting and Removing Cluster Properties
shutdown-escalation, Summary of Cluster Properties and Options
Cluster Option, Summary of Cluster Properties and Options
standard, Resource Properties
Resource, Resource Properties
start, Time/Date Based Expressions
Constraint Expression, Time/Date Based Expressions
Start Order, Order Constraints
start-failure-is-fatal, Summary of Cluster Properties and Options
Cluster Option, Summary of Cluster Properties and Options
status
display, Displaying Cluster Status
stonith-action, Summary of Cluster Properties and Options
Cluster Option, Summary of Cluster Properties and Options
stonith-enabled, Summary of Cluster Properties and Options
Cluster Option, Summary of Cluster Properties and Options
stonith-timeout, Summary of Cluster Properties and Options
Cluster Option, Summary of Cluster Properties and Options
stop-all-resources, Summary of Cluster Properties and Options
Cluster Option, Summary of Cluster Properties and Options
stop-orphan-actions, Summary of Cluster Properties and Options
Cluster Option, Summary of Cluster Properties and Options
stop-orphan-resources, Summary of Cluster Properties and Options
Cluster Option, Summary of Cluster Properties and Options
symmetric-cluster, Summary of Cluster Properties and Options
Cluster Option, Summary of Cluster Properties and Options
symmetrical, Order Constraints
Order Constraints, Order Constraints

U

utilization attributes, Utilization and Placement Strategy

W

weekdays, Date Specifications
Date Specification, Date Specifications
weeks, Date Specifications
Date Specification, Date Specifications
weekyears, Date Specifications
Date Specification, Date Specifications

Y

yeardays, Date Specifications
Date Specification, Date Specifications
years, Date Specifications
Date Specification, Date Specifications

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