This is a text-only version of the following page on https://raymii.org:
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Title       :   Corosync Pacemaker - Execute script on failover
Author      :   Remy van Elst
Date        :   20-11-2013
URL         :   https://raymii.org/s/tutorials/Corosync_Pacemaker_-_Execute_a_script_on_failover.html
Format      :   Markdown/HTML
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With Corosync/Pacemaker there is no easy way to simply run a script on failover.
There are good reasons for this, but sometimes you want to do something simple.
This tutorial describes how to change the Dummy OCF resource to execute a script
on failover.

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In this example it is a script which triggers a few SNMP traps, sends an alert
to Nagios and sends some data to Graphite. SNMP alone could be done with the
`ocf:heartbeat:ClusterMon` resource, but the other stuff not.

This is a very very simple way of doing it, I find it more a quick hack. For
example, the script path is hard coded. For me that is not a problem because
both the script as the Dummy resource are managed via Ansible, so I can change
them any time.

Start by copying the Dummy resource over to a new resource. On Ubuntu the
resource files are located here:



   /usr/lib/ocf/resource.d/heartbeat/


In there, copy the `Dummy` file to a new resource, for example `FailOverScript`.
If you don't have the Dummy resource, you can also find it [here][2].

Edit the name and description:

Name:



   meta_data() {
       cat <<END
   <?xml version="1.0"?>
   <!DOCTYPE resource-agent SYSTEM "ra-api-1.dtd">
   <resource-agent name="FailOverScript" version="0.9">
   <version>1.0</version>


Description:



   <longdesc lang="en">
   Script ran on Failover
   </longdesc>
   <shortdesc lang="en">Script ran on Failover</shortdesc>


Make sure the script you want to execute is placed on the host, and is
executable (`chmod +x /usr/local/bin/script`).

A bit lower in the file, edit the `dummy_start` function. Add the script path
below the `if [ $? = $OCF_SUCCESS ]; then` and above the `return $OCF_SUCCESS`
lines. Like so:



   dummy_start() {
       dummy_monitor
       /usr/local/bin/failover.sh
       if [ $? =  $OCF_SUCCESS ]; then
       return $OCF_SUCCESS
       fi
       touch ${OCF_RESKEY_state}
   }


After that has been done, replace all instances of Dummy and dummy with your
name of choice:



   sed -i 's/Dummy/FailOverScript' /usr/lib/ocf/resource.d/heartbeat/FailOverScript
   sed -i 's/dummy/failoverscript' /usr/lib/ocf/resource.d/heartbeat/FailOverScript


Test the script using the `ocf-tester` program to see if you have any mistakes:



   ocf-tester -n resourcename /usr/lib/ocf/resource.d/heartbeat/FailOverScript


Output:



   Beginning tests for /usr/lib/ocf/resource.d/heartbeat/FailOverScript...
   /usr/sbin/ocf-tester: 214: /usr/sbin/ocf-tester: xmllint: not found
   * rc=127: Your agent produces meta-data which does not conform to ra-api-1.dtd
   * Your agent does not support the notify action (optional)
   * Your agent does not support the demote action (optional)
   * Your agent does not support the promote action (optional)
   * Your agent does not support master/slave (optional)
   Tests failed: /usr/lib/ocf/resource.d/heartbeat/FailOverScript failed 1 tests


Oops. Seems we need `xmllint`. On Ubuntu, install it:



   apt-get install libxml2-utils


Test again, you'll see it will pass:



   Beginning tests for /usr/lib/ocf/resource.d/heartbeat/FailOverScript...
   * Your agent does not support the notify action (optional)
   * Your agent does not support the demote action (optional)
   * Your agent does not support the promote action (optional)
   * Your agent does not support master/slave (optional)
   /usr/lib/ocf/resource.d/heartbeat/FailOverScript passed all tests


As an extra test, to see if the script you've created is correctly executed, you
can do a test start of the resource:



    export OCF_ROOT=/usr/lib/ocf
    bash -x /usr/lib/ocf/resource.d/heartbeat/FailOverScript start


To use this resource, add it like so:



   crm configure primitive script ocf:heartbeat:FailOverScript op monitor interval="30"


If you want to test it, you can for example let the script send you an email.
Put a node in standby and see if you get an email.

  [1]: https://www.digitalocean.com/?refcode=7435ae6b8212
  [2]: https://github.com/ClusterLabs/resource-agents/blob/master/heartbeat/Dummy

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