Docs - Postgres Exporter - add advanced configuration options

doc/administration/monitoring/prometheus/postgres_exporter.md

@@ -8,9 +8,8 @@ The [postgres exporter] allows you to measure various PostgreSQL metrics.
 
 To enable the postgres exporter:
 
-1. [Enable Prometheus](index.md#configuring-prometheus)
-1. Edit `/etc/gitlab/gitlab.rb`
-1. Add or find and uncomment the following line, making sure it's set to `true`:
+1. [Enable Prometheus](index.md#configuring-prometheus).
+1. Edit `/etc/gitlab/gitlab.rb` and enable `postgres_exporter`:
 
    ```ruby
    postgres_exporter['enable'] = true
@@ -22,11 +21,41 @@ address is [listed in `trust_auth_cidr_addresses`](../../high_availability/datab
 exporter will not be able to connect to the database.
 
 1. Save the file and [reconfigure GitLab][reconfigure] for the changes to
-   take effect
+   take effect.
 
 Prometheus will now automatically begin collecting performance data from
 the postgres exporter exposed under `localhost:9187`.
 
+## Advanced configuration
+
+In most cases, Postgres exporter will work with the defaults and you should not
+need to change anything.
+
+The following configuration options can be used to further customize the
+Postgres exporter:
+
+1. Edit `/etc/gitlab/gitlab.rb`:
+
+   ```ruby
+   postgres_exporter['dbname'] = 'pgbouncer'           # The name of the database to connect to.
+   postgres_exporter['user'] = 'gitlab-psql'           # The user to sign in as.
+   postgres_exporter['password'] = ''                  # The user's password.
+   postgres_exporter['host'] = 'localhost'             # The host to connect to. Values that start with '/' are for unix domain sockets (default is 'localhost').
+   postgres_exporter['port'] = 5432                    # The port to bind to (default is '5432').
+   postgres_exporter['sslmode'] = 'require'            # Whether or not to use SSL. Valid options are:
+                                                    #   'disable' (no SSL),
+                                                    #   'require' (always use SSL and skip verification, this is the default value),
+                                                    #   'verify-ca' (always use SSL and verify that the certificate presented by the server was signed by a trusted CA),
+                                                    #   'verify-full' (always use SSL and verify that the certification presented by the server was signed by a trusted CA and the server host name matches the one in the certificate).
+   postgres_exporter['fallback_application_name'] = '' # An application_name to fall back to if one isn't provided.
+   postgres_exporter['connect_timeout'] = ''           # Maximum wait for connection, in seconds. Zero or not specified means wait indefinitely.
+   postgres_exporter['sslcert'] = 'ssl.crt'            # Cert file location. The file must contain PEM encoded data.
+   postgres_exporter['sslkey'] = 'ssl.key'             # Key file location. The file must contain PEM encoded data.
+   postgres_exporter['sslrootcert'] = 'ssl-root.crt'   # The location of the root certificate file. The file must contain PEM encoded data.
+   ```
+
+1. Save the file and [reconfigure GitLab][reconfigure] for the changes to take effect.
+
 [← Back to the main Prometheus page](index.md)
 
 [1131]: https://gitlab.com/gitlab-org/omnibus-gitlab/merge_requests/1131