Re: Error: pid file is invalid, please manually kill the stale server process.

On Wed, Feb 12, 2014 at 6:59 AM, Theodotos Andreou
<theo(at)theo-andreou(dot)org> wrote:
> I have a weird problem. Sometimes when the machine is restarted, there is no
> $PGDATA/postmaster.pid file. So when I try to restart postgres (service
> postgresql restart) I get the following error:
>

It is not clear what the real problem is. After a machine reboot it is
normal that there is no pid file, meaning a clean shutdown happened
(from the PostgreSQL perspective). After a full start, if the
PostgreSQL process is configured for automatic start, a pid file
should exist. I suspect the problem is related to some ubuntu booting
script that will place the pid file somewhere else from where the
pg_ctl expects to find it.

> An even scarier side-effect of this is that the data, when this happens, are
> older than the most recent data in the database.
>

This does not make sense at all. How do you know that data is older?
And most notably: is data stable? I mean, could it be some kind of
snapshotting of the database filesystem (as other suggested) or sounds
like a data corruption?

> Also postgres is installed on a customer appliance that may experience
> frequent reboots and even abrupt poweroffs! Is postgres in general ideal for
> this situation? Is there an optimal configuration for this scenario?

PostgreSQL is reliable, but even a reliable system can crash when
running on a totally unreliable piece of hardware. I suggest investing
in some good platform to avoid stressing the database with resumes.
However, in such scenario, I will choose a sync of all commits and
short checkpoints, but this will lead to bad performances.

Luca