Using Prometheus

Using Prometheus#

Scrape http(s)://<node>:<monitor_port>/metrics on each PGD node for a standard Prometheus target, served by the same monitor HTTP server as the web UI and REST API. See Monitoring metrics reference for every metric it exposes.

Enable it with bdr.monitor_enabled , the same as the web UI, and configure the shared server the same way too, using the monitor_http_port , monitor_use_https , and bdr.monitor_ssl_* parameters.

The endpoint uses HTTP Basic authentication for each scrape, sending a username and password with every request rather than a session cookie. It checks the credentials against a Postgres role that’s a member of pg_monitor , the same check the web UI login uses, so Prometheus’s basic_auth works unchanged.

Unlike the web UI, the endpoint reports only the local node’s view, since a scrape never queries other nodes, so you must configure one target per PGD node.

Note

Set bdr.monitor_prometheus_pg_metrics to off if Prometheus

postgres_exporter already runs on a node and you don't want duplicate series. Set it on each node where you want the behavior and reload the configuration. This setting controls whether Monitoring metrics reference also includes Postgres statistics families equivalent to the most useful postgres_exporter collectors, on by default. PGD-native metrics keep exporting either way.

Configuring a scrape target#

Add a job to your Prometheus configuration file, listing every PGD node as a target and supplying the pg_monitor role’s credentials for basic_auth :

scrape_configs:
  - job_name: pgd
    basic_auth:
      username: monitoring_role
      password: ...
    static_configs:
      - targets:
          - node1.example.com:6437
          - node2.example.com:6437

Metric format and conventions#

The endpoint responds with Content-Type: text/plain; version=0.0.4 , the standard Prometheus text exposition format. The following conventions apply throughout its output.

  • Counters are exported raw with the _total suffix. Compute rates in PromQL with rate() .

  • Identity (info ) metrics have the constant value 1 and carry their payload in labels, for example the Raft leader name.

  • Log sequence number (LSN) positions are exported as bytes since 0/0 , so PromQL can subtract them directly, for example sent minus replay equals apply lag in bytes.

  • Time-valued counters from Postgres statistics are converted to seconds.

  • Most metrics sample roughly every 10 seconds; a few, including disk space and the commit latency histogram, sample every 60 seconds. See Monitoring metrics reference for the exact interval and description of each metric.

The following are deliberately excluded from /metrics .

  • Per-table statistics (dead tuples, sizes, scan counts). Cardinality is unbounded across many tables, so these stay available on demand through the REST API and the web UI’s **Tables** page instead.

  • Vacuum progress. These rows are ephemeral and unsuitable for a time series, so they stay on the web UI only.

  • pg_settings , physical replication views (pg_stat_replication , pg_stat_wal_receiver ), and anything needing extra extensions, such as pg_buffercache .

  • A pg_up -style metric. The exporter runs inside the server itself, so Prometheus’s own up metric for the scrape already covers reachability.

If you need any of these as Prometheus metrics, run postgres_exporter alongside PGD Monitor. Its stat_user_tables , stat_progress_vacuum , settings , and replication collectors, all enabled by default, cover per-table statistics, vacuum progress, pg_settings , and physical replication respectively.

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