Re: koji-hub, event MPM, and postgres max_connections on el8

[Michael McLean]

I hacked up a completely naive implementation using psycopg2.pool. It seems
to work ok here on F31, but this would need a lot of clean up.

https://github.com/mikem23/koji-playground/commits/connection-pool

On Fri, May 29, 2020 at 3:27 PM Ken Dreyer <ktdreyer(a)ktdreyer.com&gt; wrote:

>  The default RHEL 7 and 8 postgresql.conf ships with
> "max_connections =
>  100".
>
>  RHEL 7's httpd uses the prefork MPM by default, and RHEL 8's httpd
>  uses the event MPM by default instead.
>
>  It seems that RHEL 8 opens many more simultaneous connections to the
>  database, and it's very easy to hit PostgreSQL's 100 max_connections
>  limit. In my tests, it's possible to get ServerOffline errors with
>  just one or two clients. For example, running kojira with kojiweb will
>  hit ServerOffline.
>
>  When I bump postgresql.conf to "max_connections = 500" I cannot reach
>  the limit on el8.
>
>  Before we tell users to bump this number in the Server HowTo guide,
>  I'm wondering if there is a better way to improve this in Koji's code.
>
>  https://wiki.postgresql.org/wiki/Number_Of_Database_Connections
>  recommends connection pooling instead of opening more connections, but
>  I don't know how to implement this.
>
>  - Ken
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