Chapter 18. Fencing the Controller Nodes
Fencing is the process of isolating a failed node to protect a cluster and its resources. Without fencing, a failed node can result in data corruption in a cluster.
The director uses Pacemaker to provide a highly available cluster of Controller nodes. Pacemaker uses a process called STONITH to fence failed nodes. STONITH is disabled by default and requires manual configuration so that Pacemaker can control the power management of each node in the cluster.
18.1. Review the Prerequisites
To configure fencing in the overcloud, your overcloud must already have been deployed and be in a working state. The following steps review the state of Pacemaker and STONITH in your deployment:
Log in to each node as the
heat-adminuser from the
stackuser on the director. The overcloud creation automatically copies the
stackuser’s SSH key to each node’s
Verify you have a running cluster:
$ sudo pcs status Cluster name: openstackHA Last updated: Wed Jun 24 12:40:27 2015 Last change: Wed Jun 24 11:36:18 2015 Stack: corosync Current DC: lb-c1a2 (2) - partition with quorum Version: 1.1.12-a14efad 3 Nodes configured 141 Resources configured
Verify STONITH is disabled:
$ sudo pcs property show Cluster Properties: cluster-infrastructure: corosync cluster-name: openstackHA dc-version: 1.1.12-a14efad have-watchdog: false stonith-enabled: false
18.2. Enable Fencing
Having confirmed your overcloud is deployed and working, you can then configure fencing:
$ openstack overcloud generate fencing --ipmi-lanplus --ipmi-level administrator --output fencing.yaml instackenv.json
parameter_defaults: EnableFencing: true FencingConfig: devices: - agent: fence_ipmilan host_mac: 11:11:11:11:11:11 params: action: reboot ipaddr: 10.0.0.101 lanplus: true login: admin passwd: InsertComplexPasswordHere pcmk_host_list: host04 privlvl: administrator
Pass the resulting
fencing.yamlfile to the
deploycommand you previously used to deploy the overcloud. This will re-run the deployment procedure and configure fencing on the hosts:
openstack overcloud deploy --templates -e /usr/share/openstack-tripleo-heat-templates/environments/network-isolation.yaml -e ~/templates/network-environment.yaml -e ~/templates/storage-environment.yaml --control-scale 3 --compute-scale 3 --ceph-storage-scale 3 --control-flavor control --compute-flavor compute --ceph-storage-flavor ceph-storage --ntp-server pool.ntp.org --neutron-network-type vxlan --neutron-tunnel-types vxlan -e fencing.yaml
The deployment command should complete without any error or exceptions.
Log in to the overcloud and verify fencing was configured for each of the controllers:
Check the fencing resources are managed by Pacemaker:
$ source stackrc $ nova list | grep controller $ ssh heat-admin@<controller-x_ip> $ sudo pcs status |grep fence stonith-overcloud-controller-x (stonith:fence_ipmilan): Started overcloud-controller-y
You should see Pacemaker is configured to use a STONITH resource for each of the controllers specified in
fence-resourceprocess should not be configured on the same host it controls.
pcsto verify the fence resource attributes:
$ sudo pcs stonith show <stonith-resource-controller-x>
The values used by STONITH should match those defined in the
18.3. Test Fencing
This procedure tests whether fencing is working as expected.
Trigger a fencing action for each controller in the deployment:
Log in to a controller:
$ source stackrc $ nova list |grep controller $ ssh heat-admin@<controller-x_ip>
As root, trigger fencing by using
iptablesto close all ports:
$ sudo -i iptables -A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT && iptables -A INPUT -p tcp -m state --state NEW -m tcp --dport 22 -j ACCEPT && iptables -A INPUT -p tcp -m state --state NEW -m tcp --dport 5016 -j ACCEPT && iptables -A INPUT -p udp -m state --state NEW -m udp --dport 5016 -j ACCEPT && iptables -A INPUT ! -i lo -j REJECT --reject-with icmp-host-prohibited && iptables -A OUTPUT -p tcp --sport 22 -j ACCEPT && iptables -A OUTPUT -p tcp --sport 5016 -j ACCEPT && iptables -A OUTPUT -p udp --sport 5016 -j ACCEPT && iptables -A OUTPUT ! -o lo -j REJECT --reject-with icmp-host-prohibited
As a result, the connections should drop, and the server should be rebooted.
From another controller, locate the fencing event in the Pacemaker log file:
$ ssh heat-admin@<controller-x_ip> $ less /var/log/cluster/corosync.log (less): /fenc*
You should see that STONITH has issued a fence action against the controller, and that Pacemaker has raised an event in the log.
Verify the rebooted controller has returned to the cluster:
From the second controller, wait a few minutes and run
pcs statusto see if the fenced controller has returned to the cluster. The duration can vary depending on your configuration.
- From the second controller, wait a few minutes and run