[Pacemaker] Signal hangup handling for pacemaker and corosync

Andrew Beekhof andrew at beekhof.net
Thu Jul 24 23:20:22 UTC 2014 

On 24 Jul 2014, at 2:46 pm, Vladislav Bogdanov <bubble at hoster-ok.com> wrote:

> 24.07.2014 03:39, Andrew Beekhof wrote:
>> 
>> 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
> 
> Yes, but it still remains racy. Strictly speaking, handler should be
> installed in the child before the parent process exits. And you cannot
> control this when shell does the fork.

I guess this is one of the few times I've been grateful for systemd

> 
>> 
>>> 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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>>>>>>>>>>>> Bugs: http://bugs.clusterlabs.org
>>>>>>>>>>>> 
>>>>>>>>>>> 
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>>>>>>>>>>> 
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>>>>>>>>>>> Bugs: http://bugs.clusterlabs.org
>>>>>>>>>> 
>>>>>>>>>> 
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>>>>>>>>>> http://oss.clusterlabs.org/mailman/listinfo/pacemaker
>>>>>>>>>> 
>>>>>>>>>> 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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>>>>>>>>> http://oss.clusterlabs.org/mailman/listinfo/pacemaker
>>>>>>>>> 
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>>>>>>>>> Getting started: http://www.clusterlabs.org/doc/Cluster_from_Scratch.pdf
>>>>>>>>> Bugs: http://bugs.clusterlabs.org
>>>>>>>> 
>>>>>>>> 
>>>>>>>> 
>>>>>>>> _______________________________________________
>>>>>>>> Pacemaker mailing list: Pacemaker at oss.clusterlabs.org
>>>>>>>> http://oss.clusterlabs.org/mailman/listinfo/pacemaker
>>>>>>>> 
>>>>>>>> Project Home: http://www.clusterlabs.org
>>>>>>>> Getting started: http://www.clusterlabs.org/doc/Cluster_from_Scratch.pdf
>>>>>>>> Bugs: http://bugs.clusterlabs.org
>>>>>>>> 
>>>>>>> 
>>>>>>> 
>>>>>>> _______________________________________________
>>>>>>> Pacemaker mailing list: Pacemaker at oss.clusterlabs.org
>>>>>>> http://oss.clusterlabs.org/mailman/listinfo/pacemaker
>>>>>>> 
>>>>>>> Project Home: http://www.clusterlabs.org
>>>>>>> Getting started: http://www.clusterlabs.org/doc/Cluster_from_Scratch.pdf
>>>>>>> Bugs: http://bugs.clusterlabs.org
>>>>>> 
>>>>>> 
>>>>>> 
>>>>>> _______________________________________________
>>>>>> Pacemaker mailing list: Pacemaker at oss.clusterlabs.org
>>>>>> http://oss.clusterlabs.org/mailman/listinfo/pacemaker
>>>>>> 
>>>>>> Project Home: http://www.clusterlabs.org
>>>>>> Getting started: http://www.clusterlabs.org/doc/Cluster_from_Scratch.pdf
>>>>>> Bugs: http://bugs.clusterlabs.org
>>>>>> 
>>>>> 
>>>>> 
>>>>> _______________________________________________
>>>>> Pacemaker mailing list: Pacemaker at oss.clusterlabs.org
>>>>> http://oss.clusterlabs.org/mailman/listinfo/pacemaker
>>>>> 
>>>>> 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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>>> 
>>> Project Home: http://www.clusterlabs.org
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>>> Bugs: http://bugs.clusterlabs.org
>> 
>> 
>> 
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>> 
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>> Bugs: http://bugs.clusterlabs.org
>> 
> 
> 
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