feat: add pg_stat_activity polling
This change adds a pg_stat_activity
polling plugin to fluentd.
- See gitlab-org&6235 (comment 609351566) for details
- Related to https://gitlab.com/gitlab-com/gl-infra/infrastructure/-/issues/13697#note_636653772
Every 2 minutes it will sample the running activity on the local postgres instance and emit the results to fluentd.
Since the plugin parses the marginalia of the activity, we can use this to build up much better profiles of which endpoints are running certain statements.
cc @dblessing as this is something you've requested in the past for understanding where in the application a specific statement is being called from.
Edited by Andrew Newdigate