[Pacemaker] Pacemaker does not handler demote/promote atomically

Andrew Beekhof andrew at beekhof.net
Tue Mar 9 02:20:20 EST 2010

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 think the pacemaker should handle demote/promote atomically, meaning it
> should prevent any PE calculation between demote and promote.
> Thanks
> hj
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