Re: Monitoring and insight into NOTIFY queue

On 02/19/2016 06:01 AM, Jiří Hlinka wrote:
> Hello,
>
> I'd like to ask you whether there is a way how to monitor and log
> details about NOTIFY queue? What do you use for this prupose?
>
> In the official documentation I'm unable to find a way how to monitor
> NOTIFY queue in more detail, at least size of this queue, which is
> critical in case of filling up the queue, which will lead to stopping
> the NOTIFY queue functionality.

Well from here:

http://git.postgresql.org/gitweb/?p=postgresql.git;a=blob;f=src/backend/commands/async.c;h=beef574076c257db0a868b39a946565185f6c53e;hb=refs/heads/REL9_5_STABLE

"There is one central queue in disk-based storage (directory pg_notify/),
with actively-used pages mapped into shared memory by the slru.c module.
All notification messages are placed in the queue and later read out
by listening backends."

and from here:

http://www.postgresql.org/docs/9.5/interactive/sql-notify.html

"The queue is quite large (8GB in a standard installation) ..."

I could see setting up file monitoring in pg_notify/ of the queue file size.

>
> Thanks,
> Jiri

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