Some postgres alerts are not related to postgres-exporter

[antoinematyja]

Hello,

We wanted to add this alert rule:

Postgresql high rate statement timeout

https://awesome-prometheus-alerts.grep.to/rules#rule-postgresql-1-12

So we installed prometheus-community/postgres_exporter (as mentioned in the title of the section).

But we quickly realized that the metric postgresql_errors_total (used in this rule) was not available with postgres_exporter.

After some research we found this pdf: https://www.postgresql.eu/events/pgconfeu2018/sessions/session/2166/slides/147/monitoring.pdf

Which presents prometheus monitoring of postgres with postgres-exporter AND using postgres logs via mtail. We can see that postgresql_errors_total is created with mtail (the mtail config file is somewhere in the middle of the pdf, search for postgresql_errors_total).

So the following alerts do not require postgres-exporter, but mtail with a custom configuration:

• Postgresql high rate statement timeout
• Postgresql high rate deadlock
  (both relying on postgresql_errors_total)

This should be mentioned next to these rules, or the rules moved to a subsection.

I looked up the original commit adding these rules:
0b89a76

It seems like it was added at the same time as the other postgres rules (which rely on postgres-exporter).

Thanks