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From: Dmitry Kovalenko <[email protected]>
To: Tom Lane <[email protected]>
Cc: [email protected]
Subject: Re: BUG #19391: pg_ctl: the PID file "/xxxx/postmaster.pid" is empty
Date: Tue, 3 Feb 2026 12:36:59 +0300
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>
	<[email protected]>

Hello,

Hope, I was able to fix this problem on a level of my code.

When I get an error "the PID file "/xxxx/postmaster.pid" is empty" I try 
to find postmaster process.

If it exists, I sleep few seconds and try to call pg_ctl again.

I am using ps + grep to find this process.

I think, it will be really useful to get this PID from "pg_ctl start" 
output instead this combination. If it possible, of course.

Thanks&Regards,

Dmitry Kovalenko

31.01.2026 4:52, Tom Lane пишет:
> PG Bug reporting form <[email protected]> writes:
>> My test framework uses "pg_ctl status ..." to detect a state of Postgres
>> instance - uninitialized, stopped, running.
>> Time from time, it returns the error - pg_ctl: the PID file
>> "/xxxx/postmaster.pid" is empty
> If you're issuing "pg_ctl status" while a postmaster is starting, it's
> possible that you're hitting the tiny window where CreateLockFile()
> has opened the file but not yet written anything into it.
>
> We could imagine making pg_ctl not treat this as an error, but
> I'm hesitant to do so because of possibly creating race conditions
> for the pg_ctl start/stop cases.  (Well, it's inherently a race
> situation if you issue two concurrent starts ... what I mean is
> that failing is the safest option in that scenario.)  Depending
> on what you intend to do with the pg_ctl status result, acting
> as if this isn't an error case could be risky there too.
> Given an empty file, we can't distinguish "a postmaster is in
> progress of starting" from "a postmaster died while starting",
> since no PID is available to test.
>
> 			regards, tom lane

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