[ClusterLabs] Pacemaker occasionally takes minutes to respond

Wed May 31 19:17:05 EDT 2017

On 05/24/2017 08:04 AM, Attila Megyeri wrote:
> Hi Klaus,
> 
> Thank you for your response.
> I tried many things, but no luck.
> 
> We have many pacemaker clusters with 99% identical configurations, package versions, and only this one causes issues. (BTW we use unicast for corosync, but this is the same for our other clusters as well.)
> I checked all connection settings between the nodes (to confirm there are no firewall issues), increased the number of cores on each node, but still - as long as a monitor operation is pending for a resource, no other operation is executed.
> 
> e.g. resource A is being monitored, and timeout is 90 seconds, until this check times out I cannot do a cleanup or start/stop on any other resource.

Do you have any constraints configured? If B depends on A, you probably
want at least an ordering constraint. Then the cluster would stop B
before stopping A, and not try to start it until A is up again.

Throttling based on load wasn't added until Pacemaker 1.1.11, so the
only limit on parallel execution in 1.1.10 was batch-limit, which
defaulted to 30 at the time.

I'd investigate by figuring out which node was DC at the time and
checking its pacemaker log (preferably with PCMK_debug=crmd turned on).
You can see each run of the policy engine and what decisions were made,
ending with a message like "saving inputs in
/var/lib/pacemaker/pengine/pe-input-4940.bz2". You can run crm_simulate
on that file to get more information about the decision-making process.

"crm_simulate -Sx $FILE -D transition.dot" will create a dot graph of
the transition showing dependencies. You can convert the graph to an svg
with "dot transition.dot -Tsvg > transition.svg" and then look at that
file in any SVG viewer (including most browsers).

> Two more interesting things: 
> - cluster recheck is set to 2 minutes, and even though the resources are running properly, the fail counters are not reduced and crm_mon lists the resources in failed actions section. forever. Or until I manually do resource cleanup.
> - If i execute a crm resource cleanup RES_name from another node, sometimes it simply does not clean up the failed state. If I execute this from the node where the resource IS actually runing, the resource is removed from the failed actions.
> 
> 
> What do you recommend, how could I start troubleshooting these issues? As I said, this setup works fine in several other systems, but here I am really-realy stuck.
> 
> 
> thanks!
> 
> Attila
> 
> 
> 
> 
> 
>> -----Original Message-----
>> From: Klaus Wenninger [mailto:kwenning at redhat.com]
>> Sent: Wednesday, May 10, 2017 2:04 PM
>> To: users at clusterlabs.org
>> Subject: Re: [ClusterLabs] Pacemaker occasionally takes minutes to respond
>>
>> On 05/09/2017 10:34 PM, Attila Megyeri wrote:
>>>
>>> Actually I found some more details:
>>>
>>>
>>>
>>> there are two resources: A and B
>>>
>>>
>>>
>>> resource B depends on resource A (when the RA monitors B, if will fail
>>> if A is not running properly)
>>>
>>>
>>>
>>> If I stop resource A, the next monitor operation of "B" will fail.
>>> Interestingly, this check happens immediately after A is stopped.
>>>
>>>
>>>
>>> B is configured to restart if monitor fails. Start timeout is rather
>>> long, 180 seconds. So pacemaker tries to restart B, and waits.
>>>
>>>
>>>
>>> If I want to start "A", nothing happens until the start operation of
>>> "B" fails - typically several minutes.
>>>
>>>
>>>
>>>
>>>
>>> Is this the right behavior?
>>>
>>> It appears that pacemaker is blocked until resource B is being
>>> started, and I cannot really start its dependency...
>>>
>>> Shouldn't it be possible to start a resource while another resource is
>>> also starting?
>>>
>>
>> As long as resources don't depend on each other parallel starting should
>> work/happen.
>>
>> The number of parallel actions executed is derived from the number of
>> cores and
>> when load is detected some kind of throttling kicks in (in fact reduction of
>> the operations executed in parallel with the aim to reduce the load induced
>> by pacemaker). When throttling kicks in you should get log messages (there
>> is in fact a parallel discussion going on ...).
>> No idea if throttling might be a reason here but maybe worth considering
>> at least.
>>
>> Another reason why certain things happen with quite some delay I've
>> observed
>> is that obviously some situations are just resolved when the
>> cluster-recheck-interval
>> triggers a pengine run in addition to those triggered by changes.
>> You might easily verify this by changing the cluster-recheck-interval.
>>
>> Regards,
>> Klaus
>>
>>>
>>>
>>>
>>>
>>> Thanks,
>>>
>>> Attila
>>>
>>>
>>>
>>>
>>>
>>> *From:*Attila Megyeri [mailto:amegyeri at minerva-soft.com]
>>> *Sent:* Tuesday, May 9, 2017 9:53 PM
>>> *To:* users at clusterlabs.org; kgaillot at redhat.com
>>> *Subject:* [ClusterLabs] Pacemaker occasionally takes minutes to respond
>>>
>>>
>>>
>>> Hi Ken, all,
>>>
>>>
>>>
>>>
>>>
>>> We ran into an issue very similar to the one described in
>>> https://bugzilla.redhat.com/show_bug.cgi?id=1430112 /  [Intel 7.4 Bug]
>>> Pacemaker occasionally takes minutes to respond
>>>
>>>
>>>
>>> But  in our case we are not using fencing/stonith at all.
>>>
>>>
>>>
>>> Many times when I want to start/stop/cleanup a resource, it takes tens
>>> of seconds (or even minutes) till the command gets executed. The logs
>>> show nothing in that period, the redundant rings show no fault.
>>>
>>>
>>>
>>> Could this be the same issue?
>>>
>>>
>>>
>>> Any hints on how to troubleshoot this?
>>>
>>> It is  pacemaker 1.1.10, corosync 2.3.3
>>>
>>>
>>>
>>>
>>>
>>> Cheers,
>>>
>>> Attila
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
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>>
>> --
>> Klaus Wenninger
>>
>> Senior Software Engineer, EMEA ENG Openstack Infrastructure
>>
>> Red Hat
>>
>> kwenning at redhat.com