| From: | Rob Brucks <rob(dot)brucks(at)rackspace(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | "David G(dot) Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com>, Adrian Klaver <adrian(dot)klaver(at)aklaver(dot)com>, "pgsql-general(at)postgresql(dot)org" <pgsql-general(at)postgresql(dot)org> |
| Subject: | Re: NOTIFY command impact |
| Date: | 2017-02-22 15:23:29 |
| Message-ID: | EFC0E80C-510A-42A1-B6E3-D55DE3D9389A@rackspace.com |
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| Lists: | pgsql-general |
Thanks Tom,
Can you answer my original question too:
If I am issuing NOTIFY commands every 30 seconds (and immediately committing) and there are no listeners, will that have a negative impact on the cluster?
I'm using the NOTIFY to force streaming replication to update the "pg_last_xact_replay_timestamp" on the slaves so we can more accurately monitor replication lag on quiet systems.
Thanks,
Rob
On 2/21/17, 5:03 PM, "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
Rob Brucks <rob(dot)brucks(at)rackspace(dot)com> writes:
> If a notify is sent and then PG is immediately shut down, wouldn't PG want to save that message for processing after startup?
> Or is the message just discarded?
NOTIFY data is not saved across a shutdown or crash.
(The reason it goes into the WAL stream is so that you can have listeners
on replication slaves, not for recovery purposes.)
regards, tom lane
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