Re: How to kill a Background worker and Its metadata

On 28 June 2016 at 02:27, Akash Agrawal <aagrawa6(at)ncsu(dot)edu> wrote:

> Hi,
>
> I've created a background worker and I am using Postgresql-9.4. This
> bgworker handles the job queue dynamically and goes to sleep if there is no
> job to process within the next 1 hour.
>
> Now, I want to have a mechanism to wake the bgworker up in case if someone
> adds a new job while the bgworker is in sleep mode. So to do it, I have
> created a trigger which initially removes the existing background worker
> and then registers a new one.
>

Don't do that.

Instead, set the background worker's process latch, which you can find in
the PGPROC array. There are a variety of examples of how to set latches in
the sources.

>
> I am retrieving the pid from pg_Stat_activity. The maximum number of
> background worker that can run simultaneously is equal to 8. I think even
> if I call pg_terminate_backend the metadata of the background worker is not
> being deleted
>

Correct. Unless you register it as a dynamic bgworker with no automatic
restart, it'll get restarted when it exits uncleanly.

Have the worker call proc_exit(0) if you want it not to be restarted.

--
Craig Ringer http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services