[ClusterLabs] Coming in Pacemaker 2.0.5: on-fail=demote / no-quorum-policy=demote

[Klaus Wenninger]

On 8/10/20 6:47 PM, Ken Gaillot wrote:
> Hi all,
>
> Looking ahead to the Pacemaker 2.0.5 release expected at the end of
> this year, here is a new feature already in the master branch.
>
> When configuring resource operations, Pacemaker lets you set an "on-
> fail" policy to specify whether to restart the resource, fence the
> node, etc., if the operation fails. With 2.0.5, a new possible value
> will be "demote", which will mean "demote this resource but do not
> fully restart it".
>
> "Demote" will be a valid value only for promote actions, and for
> recurring monitors with "role" set to "Master".
>
> Once the resource is demoted, it will be eligible for promotion again,
> so if the promotion scores have not changed, a promote on the same node
> may be attempted. If this is not desired, the agent can change the
> promotion scores either in the failed monitor or the demote.
>
> The intended use case is an application where a successful demote 
> assures a well-functioning service, and a full restart would be
> unnecessarily heavyweight. A large database might be an example.
>
> Similarly, Pacemaker offers the cluster-wide "no-quorum-policy" option
> to specify what happens to resources when quorum is lost (the default
> being to stop them). With 2.0.5, "demote" will be a possible value here
> as well, and will mean "demote all promotable resources and stop all
> other resources".
When using the new "no-quorum-policy" together with SBD please be
sure to use an SBD version that has
https://github.com/ClusterLabs/sbd/pull/111.

Klaus
>
> The intended use case is an application that cannot cause any harm
> after being demoted, and may be useful in a demoted role even if there
> is no quorum. A database that operates read-only when demoted and
> doesn't depend on any non-promotable resources might be an example.
>
> Happy clustering :)