[ClusterLabs] FYI possibly incompatible change in Corosync CPG service in master

[Jan Friesse]

I would like to inform all developers who is using Corosync CPG service 
about possibly "incompatible" change in Corosync master branch.

Previously CPG sent joinlist always contained only 1 member. This 
behavior was not entirely correct so we fixed that so now only 1 CPG 
join list confchg event with all joined members is sent by node/group.

Such change doesn't break API, because confchg callback parameter is 
array of joined members, and it was never guaranteed that callback will 
always contain only 1 member. So there is no .so version bump planned.

I'm pretty sure applications using CPG are well written and are able to 
handle described change without any problems, but better safe than sorry.

Plan is to have this change included with next stable Camelback release 
(3.0.3 - in about half of a year). There are no plans to backport this 
change into Needle (2.x) branch.

So if you are developer (or passionate user) of software which is using 
Corosync CPG then I would like to ask you to give a test to current 
master (3c7f19a02fbff19414638952043691d92be86d41) and fix/report 
problems you've found. Currently Pacemaker (thanks Ken for testing) and 
Proxmox (Fabian is author of the patch) are known to work well.

Regards,
   Honza