Re: [PATCH] Function to get size of asynchronous notification queue

I don't see this in the CF app; can you please add it there?

Best regards,

On Wed, Jun 17, 2015 at 3:31 AM, Brendan Jurd <direvus(at)gmail(dot)com> wrote:

> Hello hackers,
>
> I present a patch to add a new built-in function
> pg_notify_queue_saturation().
>
> The purpose of the function is to allow users to monitor the health of
> their notification queue. In certain cases, a client connection listening
> for notifications might get stuck inside a transaction, and this would
> cause the queue to keep filling up, until finally it reaches capacity and
> further attempts to NOTIFY error out.
>
> The current documentation under LISTEN explains this possible gotcha, but
> doesn't really suggest a useful way to address it, except to mention that
> warnings will show up in the log once you get to 50% saturation of the
> queue. Unless you happen to be eyeballing the logs when it happens, that's
> not a huge help. The choice of 50% as a threshold is also very much
> arbitrary, and by the time you hit 50% the problem has likely been going on
> for quite a while. If you want your nagios (or whatever) to say, alert you
> when the queue goes over 5% or 1%, your options are limited and awkward.
>
> The patch has almost no new code. It makes use of the existing logic for
> the 50% warning. I simply refactored that logic into a separate function
> asyncQueueSaturation, and then added pg_notify_queue_saturation to make
> that available in SQL.
>
> I am not convinced that pg_notify_queue_saturation is the best possible
> name for this function, and am very much open to other suggestions.
>
> The patch includes documentation, a regression test and an isolation test.
>
> Cheers,
> BJ
>
>
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--
Gurjeet Singh http://gurjeet.singh.im/