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The postmaster collector exposes the PostgreSQL server start time.

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Status

Default: Disabled Enable with: --collector.postmaster

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Metrics

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pg_postmaster_start_time_seconds

Type: Gauge
Description: Time at which postmaster started (Unix timestamp) Labels: None

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SQL Query

SELECT extract(epoch from pg_postmaster_start_time) 
FROM pg_postmaster_start_time();

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PostgreSQL Versions

Supported: PostgreSQL 9.1+ The pg_postmaster_start_time() function was introduced in PostgreSQL 9.1.

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Required Permissions

The monitoring user needs:
  • Execute permission on pg_postmaster_start_time() function (granted to PUBLIC by default)

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Example Output

pg_postmaster_start_time_seconds 1638360000

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Use Cases

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Tracking Uptime

Calculate server uptime: 
time() - pg_postmaster_start_time_seconds

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Detecting Restarts

Detect when PostgreSQL has restarted: 
changes(pg_postmaster_start_time_seconds[5m]) > 0

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Alert on Unexpected Restarts

- alert: PostgreSQLRestarted
  expr: changes(pg_postmaster_start_time_seconds[5m]) > 0
  annotations:
    summary: "PostgreSQL has restarted"
    description: "PostgreSQL on {{ $labels.instance }} restarted {{ $value }} times in the last 5 minutes"

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