Chapter 24. 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 allowed to run a virtual domain must have access to the necessary configuration files and storage devices for that 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.

24.1. Virtual domain resource options

Table 24.1, “Resource Options for Virtual Domain Resources” describes the resource options you can configure for a VirtualDomain resource.

Table 24.1. 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.

24.2. Creating the virtual domain resource

Use the following procedure to create a VirtualDomain resource in a cluster for a virtual machine you have previously created:

  1. To create the VirtualDomain resource agent for the management of the virtual machine, Pacemaker requires the virtual machine’s xml configuration file to be dumped to a file on disk. For example, if you created a virtual machine named guest1, dump the xml file to a file somewhere on one of the cluster nodes that will be allowed to run the guest. You can use a file name of your choosing; this example uses /etc/pacemaker/guest1.xml.

    # virsh dumpxml guest1 > /etc/pacemaker/guest1.xml
  2. Copy the virtual machine’s xml configuration file to all of the other cluster nodes that will be allowed to run the guest, in the same location on each node.
  3. Ensure that all of the nodes allowed to run the virtual domain have access to the necessary storage devices for that virtual domain.
  4. Separately test that the virtual domain can start and stop on each node that will run the virtual domain.
  5. If it is running, shut down the guest node. Pacemaker will start the node when it is configured in the cluster. The virtual machine should not be configured to start automatically when the host boots.
  6. Configure the VirtualDomain 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.

    In this example migration_transport is set to ssh. Note that for SSH migration to work properly, keyless logging must work between nodes.

    # pcs resource create VM VirtualDomain config=/etc/pacemaker/guest1.xml migration_transport=ssh meta allow-migrate=true