[ClusterLabs] Antw: Re: big trouble with a DRBD resource

[Jan Pokorný]

On 08/08/17 09:42 -0500, Ken Gaillot wrote:
> On Tue, 2017-08-08 at 10:18 +0200, Ulrich Windl wrote:
>>>>> Ken Gaillot <kgaillot at redhat.com> schrieb am 07.08.2017 um 22:26 in Nachricht
>> <1502137587.5788.83.camel at redhat.com>:
>> 
>> [...]
>>> Unmanaging doesn't stop monitoring a resource, it only prevents starting
>>> and stopping of the resource. That lets you see the current status, even
>>> if you're in the middle of maintenance or what not. You can disable
>> 
>> This feature is discussable IMHO: If you plan to update the RAs, it seems a bad idea to run the monitor (that is part of the RA). Especially if a monitor detects a problem while in maintenance (e.g. the updated RA needs a new or changed parameter), it will cause actions once you stop maintenance mode, right?
> 
> Generally, it won't cause any actions if the resource is back in a good
> state when you leave maintenance mode. I'm not sure whether failures
> during maintenance mode count toward the migration fail count -- I'm
> guessing they do but shouldn't. If so, it would be possible that the
> cluster decides to move it even if it's in a good state, due to the
> migration threshold. I'll make a note to look into that.
> 
> Unmanaging a resource (or going into maintenance mode) doesn't
> necessarily mean that the user expects that resource to stop working. It
> can be a precaution while doing other work on that node, in which case
> they may very well want to know if it starts having problems.
>  
> You can already disable the monitors if you want, so I don't think it
> needs to be changed in pacemaker. My general outlook is that pacemaker
> should be as conservative as possible (in this case, letting the user
> know when there's an error), but higher-level tools can make different
> assumptions if they feel their users would prefer it. So, pcs and crm
> are free to disable monitors by default when unmanaging a resource, if
> they think that's better.

In fact pcs follows along in this regard (i.e. conservative behaviour
per above by default), but as of 0.9.157[1] -- or rather bug-hunted
0.9.158[2] -- it allows one to disable/enable monitor operations when
unmanaging/managing (respectively) resources in one go with --monitor
modifier.  That should cater the mentioned use case.

[1] http://lists.clusterlabs.org/pipermail/users/2017-April/005459.html
[2] http://lists.clusterlabs.org/pipermail/users/2017-May/005824.html

-- 
Jan (Poki)
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