[ClusterLabs Developers] migrate-to and migrate-from for moving Master/Slave roles ?

[Jehan-Guillaume de Rorthais]

On Tue, 1 Dec 2015 11:18:07 +0100
Jehan-Guillaume de Rorthais <jgdr at dalibo.com> wrote:

> On Mon, 30 Nov 2015 15:04:37 -0600
> Ken Gaillot <kgaillot at redhat.com> wrote:
> 
> > On 11/25/2015 06:52 PM, Jehan-Guillaume de Rorthais wrote:
> > > Hi guys,
> > > 
> > > While working on our pgsqlms agent[1], we are now studying how to control
> > > all the steps of a switchover process from the resource agent. 
> > > 
> > > The tricky part here is the 2nd step of a successful swithover with
> > > PostgreSQL (9.3+):
> > >   (1) shutdown the master first
> > >   (2) make sure the designated slave received **everything** from the old
> > > master (3) promote the designated slave as master
> > >   (4) start the old master as slave
> > > 
> > > As far as we understand Pacemaker, migrate-to and migrate-from
> > > capabilities allows to distinguish if we are moving a resource because of
> > > a failure or for a controlled switchover situation. Unfortunately, these
> > > capabilities are ignored for cloned and multi-state resources...
> > > 
> > > Because of this restriction, we currently don't know from the resource
> > > agent code if we should check the designated slave received everything
> > > from the old master (controlled switchover) or not (we lost the master).
> > > In case of controlled switchover, if the designated slave did not
> > > received everything from the master, we must abort the switchover.

... 

> > It would be nice to support migration for globally unique clones, and
> > the master role of stateful clones. Feel free to submit a feature
> > request with what you think the interface should look like.
> 
> Thanks, I will.

done:

http://bugs.clusterlabs.org/show_bug.cgi?id=5259

Let me know if I can do anything. With enough direction (I don't have lot of
R&D time), I might be able to help forging a patch.

Regards,