[ClusterLabs] Master-Slaver resource Restarted after configuration change

Ilia Sokolinski ilia at clearskydata.com
Wed Jun 29 14:35:48 EDT 2016

> I'm not sure there's a way to do this.
> If a (non-reloadable) parameter changes, the entire clone does need a
> restart, so the cluster will want all instances to be stopped, before
> proceeding to start them all again.
> Your desired behavior couldn't be the default, because not all services
> would be able to function correctly with a running master using
> different configuration options than running slaves. In fact, I think it
> would be rare; consider a typical option for a TCP port -- changing the
> port in only the slaves would break communication with the master and
> potentially lead to data inconsistency.
> Can you give an example of an option that could be handled this way
> without causing problems?
> Reload could be a way around this, but not in the way you suggest. If
> your service really does need to restart after the option change, then
> reload is not appropriate. However, if you can approach the problem on
> the application side, and make it able to accept the change without
> restarting, then you could implement it as a reload in the agent.


I see what you are saying.
The parameter we are changing is the docker image version, so it is not possible to Reload it without a restart.

Couple of questions:
What is reloadable vs non-reloadable parameter? Is it the same as unique=“0” vs unique=“1”?
We currently set  unique=“0”.

When doing repeated experiments, I see that sometimes both Master and Slave are Reload-ed, but sometimes one of them is Restart-ed.

Why is that?
I looked at the source code allocate.c:check_action_definition(), and it seems that there is a meta parameter
called “isolation” which affects on Reload vs Restart decision.

I can’t find any documentation about this “isolation” meta parameter.
Do you know what is is intended for?

Thanks a lot


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