[Pacemaker] Signal hangup handling for pacemaker and corosync

[Andrew Beekhof]

On 23 Jul 2014, at 2:46 pm, Vladislav Bogdanov <bubble at hoster-ok.com> wrote:

> 23.07.2014 05:56, Andrew Beekhof wrote:
>> 
>> On 21 Jul 2014, at 3:45 pm, Vladislav Bogdanov <bubble at hoster-ok.com> wrote:
>> 
>>> 21.07.2014 08:36, Andrew Beekhof wrote:
>>>> 
>>>> On 21 Jul 2014, at 2:50 pm, Vladislav Bogdanov <bubble at hoster-ok.com> wrote:
>>>> 
>>>>> 21.07.2014 06:28, Andrew Beekhof wrote:
>>>>>> 
>>>>>> On 15 Jul 2014, at 8:45 pm, Arjun Pandey <apandepublic at gmail.com> wrote:
>>>>>> 
>>>>>>> On Tue, Jul 15, 2014 at 3:36 PM, Andrew Beekhof <andrew at beekhof.net> wrote:
>>>>>>>> 
>>>>>>>> On 15 Jul 2014, at 8:00 pm, Arjun Pandey <apandepublic at gmail.com> wrote:
>>>>>>>> 
>>>>>>>>> Right. Actually the issue i am facing is that i am starting the
>>>>>>>>> pacemaker service remotely from a wrapper and thus pacemakerd dies
>>>>>>>>> when the wrapper exits.nohup solves the problem but then HUP cannot be
>>>>>>>>> used by pacemaker. Is this workaround ok ?
>>>>>>>> 
>>>>>>>> I guess. How are you starting pacemaker?  Usually its with some variant of 'service pacemaker start'.
>>>>>>> I am using 'service pacemaker start'. However this is being called
>>>>>>> from my script. So when the script exits pacemaker gets SIGHUP.
>>>>>> 
>>>>>> Release testing starts clusters as:
>>>>>> 
>>>>>> ssh -l root somenode -- service pacemaker start
>>>>> 
>>>>> It could depend on what "service" is.
>>>>> It would either schedule systemd to run job (el7/fc18+), or just run
>>>>> init script itself (el6). In latter case, if process didn't detach from
>>>>> its controlling terminal when that terminal gone away, it will be sent a
>>>>> SIGHUP.
>>>> 
>>>> Except we test rhel6 the same way...
>>> 
>>> I understand. This issue is from "sometimes happens on some systems"
>>> folder. I recall I had problems ages ago with a daemon run from rc.local
>>> sometimes exists with HUP. 'sleep 1' after its launch was the easiest fix.
>> 
>> How about: https://github.com/beekhof/pacemaker/commit/95175f5
> 
> That doesn't hurt, but could be just not enough, as pacemakerd does not
> daemonize itself, but is put into background by shell means. Thus, when
> you add signal handler, pacemakerd already runs some time in the
> background. If terminal (ssh session) disconnects before signal handler
> is installed, then process exits anyways.

Just moving it earlier would seem the simplest option

> I'd suggest to add '-d' option and daemonize (double-fork or fork+setsid
> plus common daemonization cleanups) if it is set after signal handlers
> are installed but before main loop is run.
> Also, SIGTTIN and SIGTTOU could be added to ignore list for a daemon mode.

The meaning of those two aren't making sense to my brain today.

> 
>> 
>>> 
>>>> 
>>>>> I'd recommend adding HUP handler (f.e. ignore) or/and detach
>>>>> (setsid()) right before daemonizing.
>>>>> 
>>>>>> 
>>>>>> And I've never seen the behaviour you speak of.
>>>>>> How is what you're doing different?
>>>>>> 
>>>>>>>> 
>>>>>>>>> 
>>>>>>>>> I was checking out the current pacemaker code.setsid is called for
>>>>>>>>> each child process.However if we do this for main process to then it
>>>>>>>>> will also be detached from the terminal.
>>>>>>>>> 
>>>>>>>>> Regards
>>>>>>>>> Arjun
>>>>>>>>> 
>>>>>>>>> 
>>>>>>>>> 
>>>>>>>>> On Tue, Jul 15, 2014 at 3:01 PM, Andrew Beekhof <andrew at beekhof.net> wrote:
>>>>>>>>>> 
>>>>>>>>>> On 15 Jul 2014, at 7:13 pm, Arjun Pandey <apandepublic at gmail.com> wrote:
>>>>>>>>>> 
>>>>>>>>>>> Hi Andrew
>>>>>>>>>>> 
>>>>>>>>>>> AFAIK linux daemons don't terminate on SIGHUP.
>>>>>>>>>> 
>>>>>>>>>> Read the man page, POSIX specifies that the default action is 'term' ie. 'terminate'.
>>>>>>>>>> 
>>>>>>>>>>> They typically reload
>>>>>>>>>>> configuration on receiving this signal.Eg- rsyslogd. I thought it was
>>>>>>>>>>> safe to make this assumption here as well.
>>>>>>>>>> 
>>>>>>>>>> Not anywhere as it turns out
>>>>>>>>>> 
>>>>>>>>>>> 
>>>>>>>>>>> Regards
>>>>>>>>>>> Arjun
>>>>>>>>>>> 
>>>>>>>>>>> On Tue, Jul 15, 2014 at 2:15 PM, Andrew Beekhof <andrew at beekhof.net> wrote:
>>>>>>>>>>>> 
>>>>>>>>>>>> On 15 Jul 2014, at 6:19 pm, Arjun Pandey <apandepublic at gmail.com> wrote:
>>>>>>>>>>>> 
>>>>>>>>>>>>> Hi all
>>>>>>>>>>>>> 
>>>>>>>>>>>>> I am running pacemaker version 1.1.10-14.el6 on CentOS 6. On setting
>>>>>>>>>>>>> up cluster if I send SIGHUP to either pacemaker or corosync services ,
>>>>>>>>>>>>> they die.
>>>>>>>>>>>>> Is this a bug ? What is the intension behind this behavior?
>>>>>>>>>>>> 
>>>>>>>>>>>> Standard default I believe.
>>>>>>>>>>>> Have you run 'man 7 signal' lately?
>>>>>>>>>>>> 
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>>>>>>>>>>>> 
>>>>>>>>>>> 
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>>>>>>>>>> 
>>>>>>>>>> 
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>>>>>>>>>> 
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>>>>>>>>>> 
>>>>>>>>> 
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>>>>>>>> 
>>>>>>>> 
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>>>>>>>> 
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>>>>>>>> 
>>>>>>> 
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>>>>>>> 
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>>>>>>> Bugs: http://bugs.clusterlabs.org
>>>>>> 
>>>>>> 
>>>>>> 
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>>>>>> 
>>>>>> Project Home: http://www.clusterlabs.org
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>>>>>> Bugs: http://bugs.clusterlabs.org
>>>>>> 
>>>>> 
>>>>> 
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>>>>> 
>>>>> Project Home: http://www.clusterlabs.org
>>>>> Getting started: http://www.clusterlabs.org/doc/Cluster_from_Scratch.pdf
>>>>> Bugs: http://bugs.clusterlabs.org
>>>> 
>>>> 
>>>> 
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>>>> 
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>>>> Bugs: http://bugs.clusterlabs.org
>>>> 
>>> 
>>> 
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>>> Bugs: http://bugs.clusterlabs.org
>> 
>> 
>> 
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>> 
> 
> 
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