[Pacemaker] Pacemaker does not handler demote/promote atomically

[hj lee]

On Tue, Mar 9, 2010 at 12:20 AM, Andrew Beekhof <andrew at beekhof.net> wrote:

> On Mon, Mar 8, 2010 at 9:37 PM, hj lee <kerdosa at gmail.com> wrote:
> > Hi,
> >
> > In the typical multi-state resource agent, it changes master score on
> demote
> > or promote. Each change in master score triggers PE calculation. Suppose
> the
> > following scenario.
> > 1. Pacemaker initiates demote/promote
> > 2. demote is issued and lower the master score on the demoted node.
> > 3. promote is issued and increases the master score on the promoted node.
> >
> > The PE calculation can be kicked off between 2 and 3, then the pacemaker
> > will see two slaves in the moment. Depending on the master score it sees
> at
> > the moment, the pacemaker may promote the old master.
>
> Is this a theoretical problem or one you've seen?
> Because we'd only demote the old master if we wanted to promote a different
> one.
> And demoting the old master would make it even less likely to be
> re-promoted than before.
>
> So I don't really see the issue.
>
> I saw it in our servers. The master node is demoted and promoted again.
This is a big problem in our cluster. Once the pacemaker scheduled
demote/promote, it should complete the scheduled demote/promote. If the
pacemaker can not process this demote/promote in multistate clone, then
there will be resources having a problem.

Thanks
hj
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