Error: FATAL - Remaining Connection Slots Are Reserved for Non-Replication Superuser Connections

Issue

The following error appears:

FATAL: remaining connection slots are reserved for non-replication superuser connections

Environment

PostgreSQL destination

Resolution

To resolve the error, do the following:

1. Find the current connection slot usage and limits in PostgreSQL. Execute the following query in your PostgreSQL instance:

      select max_conn, used, res_for_super,((max_conn - res_for_super)-used) as res_for_normal
      from
      (select count(*) used from pg_stat_activity) t1,
      (select setting::int res_for_super from pg_settings
      where name='superuser_reserved_connections') t2,
      (select setting::int max_conn from pg_settings where name='max_connections') t3
   

2. Contact your database administrator to make changes as needed using the max_connections setting in the postgresql.conf file.

Cause

PostgreSQL reserves a number of connection slots for superusers. The maximum number of connections is equal to max_connections - superuser_reserved_connections. The Fivetran user won't be able to connect if all of the currently open connection slots are reserved for superusers.