[ClusterLabs] Ordering - clones & relocation

[Ken Gaillot]

On Thu, 2022-09-01 at 14:12 +0100, lejeczek via Users wrote:
> Hi guys.
> 
> This might be tricky but also can be trivial, I'm hoping for the
> latter of course.
> 
> Ordering Constraints:
> ...
> start non-clone then start a-clone-resource (kind:Mandatory)
> ...
> 
> Now, when 'non-clone' gets relocated what then happens to 'a-clone-
> resource' ?
> or.. for that matter, to any resource when 'ordering' is in play?
> Do such "dependent" resources get restarted, when source resource
> 'moves' and if yes, is it possible to have PCS do not that?
> 
> many thanks, L.

All instances of a-clone-resource will be stopped, then non-clone will
be stopped, then non-clone will be started on its new node, then all
instances of a-clone-resource will be started.

You can use interleave when ordering two clone resources so that only
the instance on the same node needs to restart, but there's no
equivalent currently for non-clone resources ordered with a clone.
(Though that is a feature I'd like to add someday.)

The closest to what you want sounds like kind=Optional on the ordering.
With an optional ordering, the dependent resource will get started
after the primary resource *if* they both need to be started, but if
only one needs to be started, the other won't be affected.
-- 
Ken Gaillot <kgaillot at redhat.com>