Re: [GENERAL] NOTIFY command impact - Mailing list pgsql-general

That's a great thought!

Comparing between systems (one where I don't issue "notify" and one where I do every minute) yields the same thing:
one8k file named "0000".
 

If that's truly where notifications are stored, then it looks like I should be good, at least for storage.  But I
wonderif that file is only used to store notify commands during shutdown/startup?
 

Or if there are any considerations for memory usage…

--Rob

On 2/21/17, 4:38 PM, "Adrian Klaver" <adrian.klaver@aklaver.com> wrote:

    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@gmail.com>
    > *Date: *Tuesday, February 21, 2017 at 3:38 PM
    > *To: *Adrian Klaver <adrian.klaver@aklaver.com>
    > *Cc: *Rob Brucks <rob.brucks@rackspace.com>,
    > "pgsql-general@postgresql.org" <pgsql-general@postgresql.org>
    > *Subject: *Re: [GENERAL] NOTIFY command impact
    >
    >
    >
    > On Tue, Feb 21, 2017 at 2:17 PM, Adrian Klaver
    > <adrian.klaver@aklaver.com <mailto:adrian.klaver@aklaver.com>> 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.
    >
    >
    >
    
    
    -- 
    Adrian Klaver
    adrian.klaver@aklaver.com