Information
The logging collector is a background process that captures log messages sent to stderr and redirects them into log files. The logging_collector setting must be enabled in order for this process to run. It can only be set at server start.
Rationale:
The logging collector approach is often more useful than logging to syslog, since some types of messages might not appear in syslog output. One common example is dynamic-linker failure message; another may be error messages produced by scripts such as archive_command.
Note: This setting must be enabled when log_destination is either 'stderr' or 'csvlog' and for certain other logging parameters to take effect.
Solution
Execute the following SQL statement(s) to remediate this setting:
postgres=# alter system set logging_collector = 'on';
ALTER SYSTEM
Unfortunately, this setting can only be changed at server (re)start. As root, restart the PostgreSQL service for this change to take effect:
$ service postgresql-9.5 restart
Stopping postgresql-9.5 service: [ OK ]
Starting postgresql-9.5 service: [ OK ]
Default Value:
on