Re: Do all superuser processes count towardsuperuser_reserved_connections?

On 3/15/19 8:16 AM, Jeremy Finzel wrote:
> On Fri, Mar 15, 2019 at 9:48 AM Adrian Klaver <adrian.klaver@aklaver.com 
> <mailto:adrian.klaver@aklaver.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.klaver@aklaver.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.klaver@aklaver.com