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
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@ktdreyer.com 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
koji-devel mailing list -- koji-devel@lists.fedorahosted.org To unsubscribe send an email to koji-devel-leave@lists.fedorahosted.org Fedora Code of Conduct: https://docs.fedoraproject.org/en-US/project/code-of-conduct/ List Guidelines: https://fedoraproject.org/wiki/Mailing_list_guidelines List Archives: https://lists.fedorahosted.org/archives/list/koji-devel@lists.fedorahosted.o...
and testing :)
On Fri, May 29, 2020 at 5:23 PM Michael McLean mikem@redhat.com wrote:
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@ktdreyer.com 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
koji-devel mailing list -- koji-devel@lists.fedorahosted.org To unsubscribe send an email to koji-devel-leave@lists.fedorahosted.org Fedora Code of Conduct: https://docs.fedoraproject.org/en-US/project/code-of-conduct/ List Guidelines: https://fedoraproject.org/wiki/Mailing_list_guidelines List Archives: https://lists.fedorahosted.org/archives/list/koji-devel@lists.fedorahosted.o...
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