Re: Do all superuser processes count toward superuser_reserved_connections?

On 3/15/19 8:16 AM, Jeremy Finzel wrote:
> On Fri, Mar 15, 2019 at 9:48 AM Adrian Klaver <adrian(dot)klaver(at)aklaver(dot)com
> <mailto:adrian(dot)klaver(at)aklaver(dot)com>> wrote:
>
> On 3/14/19 8:23 AM, Jeremy Finzel wrote:
> > I don't find a clear mention in the docs of superuser processes
> that are
> > exempt from counting toward superuser_reserved_connections.  So I
> would
> > think that it's possible that postgres autovac workers ought to
> count
> > toward that.  Am I wrong about that?  I actually have the same
> question
>
> AFAICK autovacuum workers do not use the connections referred to above.
> The details can be found here:
>
> https://doxygen.postgresql.org/autovacuum_8c.html
>
>
> Not sure I can really grok that and how it answers the question.  Are
> you saying if you have max_connections set to 10, you could
> theoretically have 20 autovac processes still?

Yes:

https://www.postgresql.org/docs/11/routine-vacuuming.html#AUTOVACUUM

"There is no limit on how many workers might be in a single database,
but workers do try to avoid repeating work that has already been done by
other workers. Note that the number of running workers does not count
towards max_connections or superuser_reserved_connections limits."

>
> > about pglogical replication background workers and manager, which
> also
> > run as postgres.
>
> But the actual connection can be by a different user:
>
> https://www.postgresql.org/docs/11/logical-replication-security.html
>
>
> But I am speaking of pglogical, which does require superuser, last I
> checked :).<mailto:adrian(dot)klaver(at)aklaver(dot)com>

Aah, my mistake I conflated pglogical with the built in logical
replication as the latter came from the former. Still:

https://www.2ndquadrant.com/en/resources/pglogical/pglogical-docs/

2.1 Quick Setup

First the PostgreSQL server has to be properly configured to support
logical decoding:

wal_level = 'logical'
max_worker_processes = 10 # one per database needed on provider node
# one per node needed on subscriber node
max_replication_slots = 10 # one per node needed on provider node
max_wal_senders = 10 # one per node needed on provider node
shared_preload_libraries = 'pglogical'

>
> It does use replication slots, but there are processes corresponding to
> each subscription.  I have some databases with dozens of them.

A process does not necessarily equal a connection.

>
> Thanks,
> Jeremy

--
Adrian Klaver
adrian(dot)klaver(at)aklaver(dot)com