document that the postgres exporter is configured automatically

howto/postgresql.md

@@ -1663,28 +1663,17 @@ PostgreSQL keeps log files in `/var/log/postgresql/`, one per
 form of SQL queries. The log rotation policy is the one set by the
 Debian package and keeps logs for 10 weeks.
 
-A [Prometheus](howto/prometheus) exporter is installed on the [GitLab](howto/gitlab) server by
-the GitLab omnibus package, but metrics are not collected on other
-Prometheus servers. The [Grafana](howto/grafana) server has a handful of
-dashboards in various working states:
+[Prometheus](howto/prometheus) monitors the PosgreSQL servers through the [PostgreSQL
+exporter]() deployed by Puppet through the
+`profile::prometheus::postgres_exporter` class.
+
+The [Grafana](howto/grafana) server has a handful of dashboards in various working
+states:
 
  * [Postgres Overview](https://grafana.torproject.org/d/wGgaPlciz/postgres-overview) - basic dashboard with minimal metrics
  * [PostgreSQL Overview (Percona)](https://grafana.torproject.org/d/IvhES05ik/postgresql-overview-percona) - mostly working
  * [GitLab Omnibus - PostgreSQL](https://grafana.torproject.org/d/c_LJgXfmk/gitlab-omnibus-postgresql) - broken
 
-We do have a Puppet class (`profile::prometheus::postgres_exporter`
-which can monitor PostgreSQL servers, but it is not deployed on all
-hosts. This is because there is still a manual step in the
-configuration of the exporter. See "installation" above.
-
-It would also be preferable if that procedure was automated in Puppet,
-but that requires haggling with the `postgresql` module which we do
-not actually use, currently. It does not directly conflict with our
-`postgres` module, but it does rewrite the `pg_hba.conf` and
-`postges.conf`. If we do eventually fix this oddity, know that we
-considered using `postgresql::server::grant`, but it might be better
-to call `postgresql_psql` directly.
-
 Note that there is a program called [pgstatsmon](https://github.com/joyent/pgstatsmon) which can provide
 very detailed information about the state of a PostgreSQL database,
 see [this blog post for details](https://www.davepacheco.net/blog/2019/visualizing-postgresql-vacuum-progress/).