[ClusterLabs] Coming in Pacemaker 2.0.5: better start-up/shutdown coordination with sbd

[Klaus Wenninger]

On 8/21/20 8:55 PM, Vladislav Bogdanov wrote:
> Hi,
>
> btw, is sbd is now able to handle cib diffs internally?
> Last time I tried to use it with frequently changing CIB, it became a
> CPU hog - it requested full CIB copy on every change.
Actually sbd should have been able to handle cib-diffs since ever.
Are you sure it requested a full copy of the CIB with every change?
Atm it should request a full update roughly twice every watchdog-timeout
and in between just noop-pings to the cib-api - as long as imbedding the
diffs goes OK of course.
In general we need full cib-updates as otherwise loss of a cib-diff
would mean possibly missing node-state updates.
What it on top does is convert the cib to a cluster-state roughly
every second or with every 10th cib-diff. The latter might impose
some cpu-usage when cib is updating at a high rate of course and
might not be really needed.
With the new pacemakerd-API we don't need the cib-diffs anymore
for graceful-shutdown-detection. Thus easiest might be to disable
diff-handling completely when pacemakerd-API is used.
>
>
> Fri, 21/08/2020 в 13:16 -0500, Ken Gaillot wrote:
>> Hi all,
>> Looking ahead to the Pacemaker 2.0.5 release expected toward the end of
>> this year, we will have improvements of interest to anyone running
>> clusters with sbd.
>> Previously at start-up, if sbd was blocked from contacting Pacemaker's
>> CIB in a way that looked like pacemaker wasn't running (SELinux being a
>> good example), pacemaker would run resources without protection from
>> sbd. Now, if sbd is running, pacemaker will wait until sbd contacts it
>> before it will start any resources, so the cluster is protected in this
>> situation.
>> Additionally, sbd will now periodically contact the main pacemaker
>> daemon for a status report. Currently, this is just an immediate
>> response, but it ensures that the main pacemaker daemon is responsive
>> to IPC requests. This is a bit more assurance that pacemaker is not
>> only running, but functioning properly. In future versions, we will
>> have even more in-depth health checks as part of this feature.
>> Previously at shutdown, sbd determined a clean pacemaker shutdown by
>> checking whether any resources were running at shutdown. This would
>> lead to sbd fencing if pacemaker shut down in maintenance mode with
>> resources active. Now, sbd will determine clean shutdowns as part of
>> the status report described above, avoiding that situation.
>> These behaviors will be controlled by a new option in
>> /etc/sysconfig/sbd or /etc/default/sbd, SBD_SYNC_RESOURCE_STARTUP. This
>> defaults to "no" for backward compatibility when a newer sbd is used
>> with an older pacemaker or vice versa. Distributions may change the
>> value to "yes" since they can ensure both sbd and pacemaker versions
>> support it; users who build their own installations can set it
>> themselves if both versions support it.
>
>
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