[ClusterLabs] dovecot RA

[Ken Gaillot]

On 06/08/2016 09:11 AM, Ken Gaillot wrote:
> On 06/08/2016 03:26 AM, Jan Pokorný wrote:
>> On 07/06/16 14:48 -0500, Dimitri Maziuk wrote:
>>> next question: I'm on centos 7 and there's no more /etc/init.d/<most
>>> anything>. With lennartware spreading, is there a coherent plan to deal
>>> with former LSB agents?
>>
>> Pacemaker can drive systemd-managed services for quite some time.
> 
> This is as easy as changing lsb:dovecot to systemd:dovecot.
> 
> Or, if you specify it as service:dovecot, Pacemaker will check whether
> LSB, systemd or upstart is used on the local system, and call the
> appropriate one.
> 
> As with LSB, don't enable systemd-managed services to start at boot, if
> you want the cluster to manage them.
> 
> One issue that sometimes comes up: some scripts (some logrotate conf
> files or cron jobs, for example) will call "systemctl reload
> <servicename>". If the service is managed by the cluster, systemd
> doesn't think it's running, so the reload will fail. You have to replace
> such lines with a native reload mechanism for the service.

Whoops -- I was thinking of when an OCF agent is used. If you use
systemd: or service:, systemd does know the service is running, so
systemctl reload/status will work just fine.

>> Provided that the project/daemon you care about carries the unit
>> file, you can use that unless there are distinguished roles for the
>> provided service within the cluster (like primary+replicas), there's
>> a need to run multiple varying instances of the same service,
>> or other cluster-specific features are desired.
>>
>> For dovecot, I can see:
>> # rpm -ql dovecot | grep \.service
>> /usr/lib/systemd/system/dovecot.service 
>>
>>> Specifically, should I roll my own RA for dovecot or is there one in the
>>> works somewhere?
>>
>> If you miss something with the generic approach per above, and there's
>> no fitting open-sourced RA around then it's probably your last resort.
>>
>> For instance, there was once an agent written in C (highly unusual),
>> but seems abandoned a long time ago:
>> https://github.com/perrit/dovecot-ocf-resource-agent