Using the PGD Monitor

Using the PGD Monitor#

PGD Monitor is a built-in monitoring web application served by every PGD node. It runs as a background worker inside the Postgres instance, requiring no separate installation, deployment, or database connection. It provides:

  • a web UI for interactive troubleshooting

  • a JSON REST API under /api/v1/ , exposing the same data the UI renders

  • a Prometheus scrape endpoint at /metrics , for feeding an existing observability stack

  • health probes at /is-live and /is-ready for orchestration

PGD Monitor doesn’t replace the SQL-level monitoring interfaces covered in Monitoring through SQL . It builds on top of those, plus the standard Postgres statistics views, through a shared metric registry. See Monitoring metrics reference for the full list of metrics this registry collects, and bdr.ts_metrics() for querying it directly over SQL.

Enabling and configuring PGD Monitor#

Enable PGD Monitor on every node that will serve it:

  1. Set bdr.monitor_enabled to on in the node’s postgresql.conf , or run ALTER SYSTEM SET bdr.monitor_enabled = 'on' .

  2. Reload the configuration: SELECT pg_reload_conf(); . No restart is required.

Once enabled, the HTTP server listens on the same addresses as Postgres, on a port 1005 higher than the Postgres port by default. For example, a node running Postgres on port 5432 serves PGD Monitor on port 6437.

To use a different port or turn on HTTPS, set the monitor_http_port node group options with bdr.alter_node_group_option . Unlike bdr.monitor_enabled , these settings are node group options, set once and inherited by every member node. For example:

SELECT bdr.alter_node_group_option(top_group, monitor_http_port, 8443);
SELECT bdr.alter_node_group_option(top_group, monitor_use_https, true);

HTTPS reuses the server’s SSL certificate configuration by default. To use different certificate files, set bdr.monitor_ssl_cert_file on each node individually, then reload the configuration.

Using PGD Monitor#

You can also authenticate against the REST API with a Postgres role name and password, using a role that’s a member of Postgres’s pg_monitor predefined role, or a superuser. The REST API may change between releases, so treat the following as best-effort rather than a stable integration point:

#  Log in and save the session cookie.

curl -c cookies.txt -X POST https://node1.example.com:6437/api/v1/login \
  -H "Content-Type: application/json" \
  -d {"username": "monitoring_role", "password": "..."}

#  Reuse the cookie for subsequent authenticated requests.

curl -b cookies.txt https://node1.example.com:6437/api/v1/cluster/health
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