[ClusterLabs] set node in maintenance - stop corosync - node is fenced - is that correct ?

[Digimer]

On 2017-10-16 03:20 PM, Lentes, Bernd wrote:
> 
> 
> ----- On Oct 16, 2017, at 7:38 PM, Digimer lists at alteeve.ca wrote:
> 
>> On 2017-10-16 01:24 PM, Lentes, Bernd wrote:
>>> Hi,
>>>
>>> i have the following behavior: I put a node in maintenance mode, afterwards stop
>>> corosync on that node with /etc/init.d/openais stop.
>>> This node is immediately fenced. Is that expected behavior ? I thought putting a
>>> node into maintenance does mean the cluster does not care anymore about that
>>> node.
>>>
>>> OS on my nodes is SLES 11 SP4.
>>>
>>> Thanks.
>>>
>>>
>>> Bernd
>>
>> Well, if you stop corosync, it would appear to leave gracefully from
>> corosync's perspective so the other node should know that it didn't
>> fail. However, and I am not a pacemaker expert, I would guess that
>> pacemaker just saw the membership change that it wasn't expecting and
>> invoked a fence.
>>
>> If you plan to remove a node, it is probably best to stop pacemaker,
>> then stop corosync.
>>
>> Also, 'openais' is oooold. Is this an old cluster? Corosync came out of
>> the openais project.
> 
> Well, OS is SLES 11 SP4. That's not the most recent one.
> Pacmekaer is 1.1.12. I didn't plan to remove the node, but to do some maintenance on it.
> 
> If i put the node in standby, then i can invoke "/etc/init.d/openais stop" without that node getting fenced.
> But then all resources on that node are stopped/migrated. If i don't want that, i thought maintenance is the right way.
> Am i wrong ?
> 
> Ah, i just saw that i wasn't complete clear. The node is fenced after stopping openais, not after putting it into maintenance.
> I did that via "crm node maintenance <node>"
> 
> Bernd

I understood what you meant about it getting fenced after stopping
corosync. What I am not clear on is if you are stopping corosync on the
normal node, or the node that is in maintenance mode.

In either case, as I understand it, maintenance mode doesn't stop
pacemaker, so it can still react to the sudden loss of membership.

I wonder; Why are you stopping corosync? If you want to stop the node,
why not stop pacemaker entirely first?

-- 
Digimer
Papers and Projects: https://alteeve.com/w/
"I am, somehow, less interested in the weight and convolutions of
Einstein’s brain than in the near certainty that people of equal talent
have lived and died in cotton fields and sweatshops." - Stephen Jay Gould