Unable to add PostgreSQL server to Plesk: A database server with this combination of host address and port number is already registered

Symptoms

• When trying to add a new PostgreSQL server at Tools & Settings > Database Servers and specifying the option Host name or IP address as localhost and leaving the Port number field blank, the following error is shown after clicking OK:

  PLESK_ERROR: Error: A database server with this combination of host address and port number is already registered.

• PostgreSQL is installed on a server with Plesk using instructions from the PostgreSQL official wiki.

Cause

Record about PostgreSQL server with the hostname
localhost
and port 5432 already exists in the Plesk system database
psa.

This is a Plesk bug with ID PPPM-6955, which is planned to be fixed in future Plesk updates.

Resolution

Until a fix becomes available, add a new PostgreSQL server specifying 127.0.0.1 as a Host name or IP address.