PostgresqlUnusedReplicationSlot

PostgresqlUnusedReplicationSlot #

Unused Replication Slots

Alert Rule
alert: PostgresqlUnusedReplicationSlot
annotations:
  description: |-
    Unused Replication Slots
      VALUE = {{ $value }}
      LABELS = {{ $labels }}    
  runbook: https://srerun.github.io/prometheus-alerts/runbooks/postgres-exporter/postgresqlunusedreplicationslot/
  summary: Postgresql unused replication slot (instance {{ $labels.instance }})
expr: pg_replication_slots_active == 0
for: 1m
labels:
  severity: warning

Here is a runbook for the PostgresqlUnusedReplicationSlot alert rule:

Meaning #

This alert is triggered when a PostgreSQL instance has an unused replication slot, indicating that a replication slot is not being utilized. This can lead to inefficient resource allocation and potential performance issues.

Impact #

The impact of an unused replication slot can be significant, as it can:

  • Waste system resources (e.g., CPU, memory, and disk space)
  • Lead to performance degradation due to unnecessary replication overhead
  • Cause confusion and complexity in database administration
  • Potentially indicate a misconfiguration or forgotten replication setup

Diagnosis #

To diagnose the issue, follow these steps:

  1. Check the PostgreSQL instance logs for any error messages related to replication.
  2. Verify that the replication slot is not being used by any standby nodes or applications.
  3. Review the PostgreSQL configuration files (e.g., postgresql.conf) to ensure that replication is properly configured.
  4. Use the pg_replication_slots view to inspect the current replication slot status.
  5. Check for any recent changes to the PostgreSQL configuration or the addition of new replication slots.

Mitigation #

To mitigate the issue, follow these steps:

  1. Identify the unused replication slot and its corresponding slot name.
  2. Drop the unused replication slot using the pg_drop_replication_slot function.
  3. Verify that the replication slot has been successfully dropped by checking the pg_replication_slots view.
  4. Review and update the PostgreSQL configuration files to ensure that replication is properly configured and optimized.
  5. Monitor the PostgreSQL instance for any further issues or performance degradation.

Remember to consult the PostgreSQL documentation and seek expert advice if you are unsure about the diagnosis or mitigation steps.

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