From: | Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com> |
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To: | Robert Haas <robertmhaas(at)gmail(dot)com>, Kuntal Ghosh <kuntalghosh(dot)2007(at)gmail(dot)com> |
Cc: | Petr Jelinek <petr(dot)jelinek(at)2ndquadrant(dot)com>, Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com>, Noah Misch <noah(at)leadboat(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Craig Ringer <craig(at)2ndquadrant(dot)com>, Michael Paquier <michael(dot)paquier(at)gmail(dot)com>, PostgreSQL mailing lists <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Why does logical replication launcher set application_name? |
Date: | 2017-06-07 02:58:24 |
Message-ID: | 0d795703-a885-2193-2331-f00d7a3a4e42@2ndquadrant.com |
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On 6/6/17 15:58, Robert Haas wrote:
> The problem with the status quo (after Peter's commit) is that there's
> now nothing at all to identify the logical replication launcher, apart
> from the wait_event field, which is likely to be LogicalLauncherMain
> fairly often if you've got the launcher. I don't personally see why
> we can't simply adopt Tom's original proposal of setting the query
> string to something like "<logical replication launcher>" which, while
> maybe not as elegant as providing some way to override the
> backend_type field, would be almost no work and substantially better
> for v10 than what we've got now.
The decision was made to add background workers to pg_stat_activity, but
no facility was provided to tell the background workers apart. Is it
now the job of every background worker to invent a hack to populate some
other pg_stat_activity field with some ad hoc information? What about
other logical replication worker types, parallel workers, external
background workers, auto-prewarm?
I think the bgw_type addition that I proposed nearby would solve this
quite well, but it needs a bit of work. And arguably, it's too late for
PG10, but one could also argue that this is a design fault in the
pg_stat_activity extension that is valid to fix in PG10.
--
Peter Eisentraut http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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