Re: What happens if the socket lock file is deleted?

On 1/29/26 12:29, stevej(at)stevej(dot)name wrote:
> In software I have developed separately, I have noticed that most systems will periodically delete files within the temporary directory hierarchy that have not been accessed recently, and that includes lock files for long running processes. I have never noticed the lock file associated with a postgreSQL socket be missing though.
>
> Does PostgreSQL periodically touch the lock file so it won’t be deleted? Alternatively, does PostgreSQL simply re-create the lock file if it has been deleted? I know the documentation says to never “manually”’delete one of those lock files.
>

From here at ~line 1781:

https://github.com/postgres/postgres/blob/master/src/backend/postmaster/postmaster.c

/*
* Once a minute, verify that postmaster.pid hasn't been removed or
* overwritten. If it has, we force a shutdown. This avoids having
* postmasters and child processes hanging around after their database
* is gone, and maybe causing problems if a new database cluster is
* created in the same place. It also provides some protection
* against a DBA foolishly removing postmaster.pid and manually
* starting a new postmaster. Data corruption is likely to ensue from
* that anyway, but we can minimize the damage by aborting ASAP.
*/
if (now - last_lockfile_recheck_time >= 1 * SECS_PER_MINUTE)
{
if (!RecheckDataDirLockFile())
{
ereport(LOG,
(errmsg("performing immediate shutdown because data directory lock
file is invalid")));
kill(MyProcPid, SIGQUIT);
}
last_lockfile_recheck_time = now;
}

--
Adrian Klaver
adrian(dot)klaver(at)aklaver(dot)com