[Pacemaker] Custom event script during master/slave failover?

[David Vossel]

----- Original Message -----
> From: "Cal Heldenbrand" <cal at fbsdata.com>
> To: "The Pacemaker cluster resource manager" <pacemaker at oss.clusterlabs.org>
> Sent: Friday, November 9, 2012 4:29:05 PM
> Subject: [Pacemaker] Custom event script during master/slave failover?
> 
> 
> Hi everyone,
> 
> I'm playing around with the possibility of using Pacemaker in a Redis
> master/slave cluster. The difficult part of this, is that Redis will
> not automatically flip itself from read-only slave mode into master
> mode. A client needs to connect to the slave server and run this
> SLAVEOF NO ONE command to turn it into a master.

The resource agent should be able to do this. Pacemaker will tell the resource agent to promote/demote a resource.  Your Redis agent can then go off and do whatever logic is necessary to actually transition the process a master/slave process.

> 
> If I set up a master/slave primitive, is it possible to fire an event
> script during a failover event that would allow me to do this?
>
> After the stonith event fires and the broken master reboots,
> I would
> write in something special in the Redis init.d script to detect if
> my peer is already a master, and start up in slave mode.

If you are using Pacemaker, it should be controlling what node has the master resource and what node has the slave resource.  Take a look at what OCF scripts are and how pacemaker uses them.

> 
> Has anyone else worked up a cluster config with Redis?

Using google, found some work someone did on a redis resource agent.
https://github.com/martinwalter/resource-agents/blob/master/heartbeat/redis

-- Vossel
> Thank you,
> 
> --Cal
> 
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