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

[Jake Smith]

----- Original Message ----- 

> From: "Cal Heldenbrand" <cal at fbsdata.com>
> To: "The Pacemaker cluster resource manager"
> <pacemaker at oss.clusterlabs.org>
> Sent: Monday, November 12, 2012 4:27:02 PM
> Subject: Re: [Pacemaker] Custom event script during master/slave
> failover?

> I've managed to get a test Redis configuration up and running...
> however this is the first time I've played with a master/slave
> resource, and I'm noticing some odd behavior in the monitoring
> actions. Setting in a super quick monitoring interval of 1 second, I
> noticed at first only the slave was being monitored, 2x in each
> second. Then after changing a bunch of config options and several
> cluster restarts, I noticed the monitoring action had moved to the
> master, again 2x events in each second.

> redis(redis:1)[2203]: 2012/11/12_15:17:52 INFO: redis-server is
> running (PID 30759)
> redis(redis:1)[2203]: 2012/11/12_15:17:52 INFO: redis-server is
> running (PID 30759)
> redis(redis:1)[2203]: 2012/11/12_15:17:52 INFO: redis-server is
> running (as master)
> redis(redis:1)[2203]: 2012/11/12_15:17:52 INFO: redis-server is
> running (as master)

> Here is my primitive and master/slave definition:

> primitive redis ocf:heartbeat:redis \
> meta target-role="Master" is-managed="true" \
> op monitor interval="1s" role="Master" timeout="5s" on-fail="restart"
> ms redis_clone redis \
> meta notify="true" is-managed="true" ordered="false"
> interleave="false" globally-unique="false" target-role="Master"
> migration-threshold="1"

> I'd like to figure out how to make sure both master and slave are
> actively monitored. Let me know if you need any more info on my
> config!

Not positive but I think you need to define the monitor action for each role specifically.  I vaguely recall something about not specifying the exact same interval for both roles also but that may not be true.  Here's an example from a DRBD master/slave resource:

primitive p_drbd_samba ocf:linbit:drbd \
        params drbd_resource="samba" \
        operations $id="p_drbd_samba-operations" \
        op start interval="0" timeout="240" \
        op stop interval="0" timeout="100" \
        op monitor interval="30" role="Slave" \
        op monitor interval="20" role="Master"

HTH

Jake

> On Fri, Nov 9, 2012 at 4:52 PM, David Vossel < dvossel at redhat.com >
> wrote:

> > ----- 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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> 
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> 
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> 
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> 

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