details on postgres metrics

howto/postgresql.md

@@ -732,6 +732,14 @@ dashboards in various working states:
  * [PostgreSQL Overview (Percona)](https://grafana.torproject.org/d/IvhES05ik/postgresql-overview-percona) - mostly working
  * [Postgres Overview](https://grafana.torproject.org/d/wGgaPlciz/postgres-overview) - basic dashboard with minimal metrics
 
+We do have a Puppet class (`profile::prometheus::postgres_exporter`
+which can monitor PostgreSQL servers, but it is not deployed on
+servers at the time of writing.
+
+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/).
+
 ## Backups
 
 We use upstream's [Continuous Archiving and Point-in-Time Recovery