[ClusterLabs] Coming in Pacemaker 2.1.3: multiple-active=stop_unexpected

[Ken Gaillot]

Hi all,

I'm hoping to have the first release candidate for Pacemaker 2.1.3
available in a couple of weeks.

One of the new features will be a new possible value for the "multiple-
active" resource meta-attribute, which specifies how the cluster should
react if multiple instances of a resource are detected to be active
when only one should be.

The default behavior, "restart", stops all the instances and then
starts one instance where it should be. This is the safest approach
since some services become disrupted when multiple copies are started.

However if the user is confident that only the extra copies need to be
stopped, they can now set multiple-active to "stop_unexpected". The
instance that is active where it is supposed to be will not be stopped,
but all other instances will be.

If any resources are ordered after the multiply active resource, those
other resources will still need to be fully restarted. This is because
any ordering constraint "start A then start B" implies "stop B then
stop A", so we can't stop the wrongly active instances of A until B is
stopped.
-- 
Ken Gaillot <kgaillot at redhat.com>