Thread: [GENERAL] Suddenly - LOG: could not open file "postmaster.pid": No such fileor directory

Muhammad Hanif Abdul Hamid <hanif.hamid@mimos.my> writes:
> Within this week, I have faced two times "postmaster.pid" went missing in a sudden. Nobody deleted it or shutdown the
server.

I'd lay very long odds that your second statement is false.  *Something*
removed that file, and it wasn't the postmaster.

            regards, tom lane

On Fri, Jun 23, 2017 at 1:43 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Muhammad Hanif Abdul Hamid <hanif.hamid@mimos.my> writes:
>> Within this week, I have faced two times "postmaster.pid" went missing in a sudden. Nobody deleted it or shutdown
theserver. 
>
> I'd lay very long odds that your second statement is false.  *Something*
> removed that file, and it wasn't the postmaster.

Yup, and the postmaster is designed to stop if it finds out that
postmaster.pid is removed. See that:
commit: 7e2a18a9161fee7e67642863f72b51d77d3e996f
author: Tom Lane <tgl@sss.pgh.pa.us>
date: Tue, 6 Oct 2015 17:15:52 -0400
Perform an immediate shutdown if the postmaster.pid file is removed
--
Michael

Hi,

Thanks for your reply, Tom and Michael.

Maybe an irrelevant question, but I would like to know if there anything from postgres process (e.g any parameter that
isnot set right) that might remove the postmaster.pid?
 

FYI, we have 20 other sites with the same database use but have not experienced this problem.

Thank you.

-----Original Message-----
From: Michael Paquier [mailto:michael.paquier@gmail.com]
Sent: Jumaat, 23 Jun 2017 1:26 ptg
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Muhammad Hanif Abdul Hamid <hanif.hamid@mimos.my>; pgsql-general@postgresql.org
Subject: Re: [GENERAL] Suddenly - LOG: could not open file "postmaster.pid": No such file or directory

On Fri, Jun 23, 2017 at 1:43 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Muhammad Hanif Abdul Hamid <hanif.hamid@mimos.my> writes:
>> Within this week, I have faced two times "postmaster.pid" went missing in a sudden. Nobody deleted it or shutdown
theserver.
 
>
> I'd lay very long odds that your second statement is false.
> *Something* removed that file, and it wasn't the postmaster.

Yup, and the postmaster is designed to stop if it finds out that postmaster.pid is removed. See that:
commit: 7e2a18a9161fee7e67642863f72b51d77d3e996f
author: Tom Lane <tgl@sss.pgh.pa.us>
date: Tue, 6 Oct 2015 17:15:52 -0400
Perform an immediate shutdown if the postmaster.pid file is removed
--
Michael

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    Muhammad Hanif Abdul Hamid wrote:

> Maybe an irrelevant question, but I would like to know if there anything
> from postgres process (e.g any parameter that is not set right) that might
> remove the postmaster.pid?

If using Linux, you may put it under watch with

# auditctl -w /path/to/postmaster.pid  -k pgpid

If that records too many events, it can be filtered further, for
example this should catch only deletions:

# auditctl -a exit,always -F path=/path/to/postmaster.pid \
    -F arch=b64 -S unlink -S unlinkat -k pgpid

Once in effect, the records about which process/user/command
deletes the file and when would be obtained with:

# ausearch -k pgpid


Best regards,
--
Daniel Vérité
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Twitter: @DanielVerite