The Misc metrics group provides details on:
- Open locks in the database cluster
- Which node is currently the leader / master (i.e. accepting writes)
- Node uptime
Provides a count of the number of open locks across the database cluster. To see more detailed information (e.g. what kinds of locks are active), open a psql terminal and run:
select relation::regclass, * from pg_locks where not granted;
For further information on locks in Postgresql, see the official documentation.
Provides historical data on which node is acting as the master for the cluster. In a streaming replication cluster, only one node can accept writes serving as the master and replicating those changes to other nodes.
For further information on replication, see the official documentation.
Provides historical data on which nodes are running. For example, if one of the Postgresql servers in the cluster was restarted as part of maintenance operations, it would return a value of “0” for the period that it was unavailable.