Horton

SV: Problem with pg_notify / listen

Mikael Gustavsson <mikael.gustavsson@smhi.se>

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From: Gustavsson Mikael <mikael.gustavsson@smhi.se>
To: "David G. Johnston" <david.g.johnston@gmail.com>
Cc: pgsql-generallists.postgresql.org <pgsql-general@lists.postgresql.org>, Svensson Peter <peter.svensson@smhi.se>, Almen Anders <anders.almen@smhi.se>
Date: 2020-11-27T14:48:28Z
Lists: pgsql-bugs

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Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Fix a recently-introduced race condition in LISTEN/NOTIFY handling.

  2. Prevent concurrent SimpleLruTruncate() for any given SLRU.

Hi David,


Thanks for fast reply!


We had to restart the server to avoid problems with a full queue så process is no longer with us.

The queue is at 25% now and we have minimised the payload to avoid problems during the weekend.
# select * from pg_notification_queue_usage()
;
 pg_notification_queue_usage
-----------------------------
           0.245367050170898
(1 row)

If my calculations is correct we will reach 50% on monday.

kr
/Mikael Gustavsson

________________________________
Från: David G. Johnston <david.g.johnston@gmail.com>
Skickat: den 27 november 2020 15:28
Till: Gustavsson Mikael
Kopia: pgsql-generallists.postgresql.org; Svensson Peter; Almen Anders
Ämne: Re: Problem with pg_notify / listen

On Friday, November 27, 2020, Gustavsson Mikael <mikael.gustavsson@smhi.se<mailto:mikael.gustavsson@smhi.se>> wrote:

Hi.

After applying the latest patch we have encountered a problem with the pg_notify queue.

The queue is filling up and starts issuing warnings like
WARNING:  NOTIFY queue is 87% full
DETAIL:  The server process with PID 2969993 is among those with the oldest transactions.
NOTIFY queue cannot be emptied until that process ends its current transaction.

There is no long-running 'active' or 'idle in transaction' transactions on the server.


As its easy enough to run can you please confirm this by showing us the pg_stat_activity record for that pid during the time when this warning appears?

Thanks!

David J.