Introduction
The Calendars and Contacts Server service uses PostgreSQL as its backend, and by default has a max_connections limit of 64. Since each worker process maintains a connection to PostgreSQL, systems with a large number of CPU cores may reach that limit and see a message such as:
[caldav-59] pg8000.core.ProgrammingError: (u'FATAL', u'FATAL', u'53300', u'sorry, too
many clients already', u'proc.c', u'346', u'InitProcess', u'', u'')
Procedure
To increase this limit, run the below command:
echo "PGMAXCONNECTIONS=128" >> /var/cpanel/ccs/config
Afterward, rebuild the CCS configuration and restart the service:
/opt/cpanel-ccs/bin/rebuildccsconfig && /scripts/restartsrv_cpanel_ccs