On 02/21/2017 02:19 PM, Rob Brucks wrote:
I did find a post a while back saying they were discarded, but I wanted to double-check. I performed some tests to see if listens worked AFTER the notify was issued, they were not. This leads me to believe that the messages are discarded when a listen does not yet exist.
Seems the thing to do would be to monitor the size of : $PG_DATA/pg_notify/
--Rob *From: *"David G. Johnston" <david.g.johnston@xxxxxxxxx> *Date: *Tuesday, February 21, 2017 at 3:38 PM *To: *Adrian Klaver <adrian.klaver@xxxxxxxxxxx> *Cc: *Rob Brucks <rob.brucks@xxxxxxxxxxxxx>, "pgsql-general@xxxxxxxxxxxxxx" <pgsql-general@xxxxxxxxxxxxxx> *Subject: *Re: NOTIFY command impact On Tue, Feb 21, 2017 at 2:17 PM, Adrian Klaver <adrian.klaver@xxxxxxxxxxx <mailto:adrian.klaver@xxxxxxxxxxx>> wrote: On 02/21/2017 01:07 PM, Rob Brucks wrote: Do you see any long-term problems with constantly issuing "NOTIFY" commands every 30 seconds without an associated "LISTEN" command? Depending on how long 'long term' is: https://www.postgresql.org/docs/9.6/static/sql-notify.html "There is a queue that holds notifications that have been sent but not yet processed by all listening sessions Its not clear in the OP that this is the case (it seems to be) but the documentation is non-specific as to what happens when "# of listeners" = 0; I suspect that said messages are created and then immediately discarded - though apparently they do make it over to the standby server too - and likely also immediately discarded there as well. David J.
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