I don't remember having used postgres ever and I forget everything I ever knew about IT very fast but here go two (maybe silly) ideas: I assume you have checked postgres server logs for errors, so the one I can add is to check if socket file is locked by any other process.

I just remembered another test: Try to telnet/SSH to the IP:Port of postgres server and check if something helpful info comes out.

EVAnaRkISTO at 2021-02-09T12:12:35Z

different port in this case, but the issue is actually with pcp_recovery_node part of pgpool.

[postgres@521 ~]$ pcp_recovery_node -h 10.14.202.76 -p 9898 -U pgpool -n 1
Password:
ERROR: connection to host "10.14.202.76" failed with error "Connection refused"

[postgres@521 data]$ psql -d postgres -h 10.14.202.76 -U pgpool -c "select count from public._test"
count
-------
5
(1 row)

The pgpool docs for anyone curious: https://www.pgpool.net/docs/latest/en/html/index.html

Doug Whitfield at 2021-02-09T14:29:01Z

not SELinux on this one machine:

SELinux status:                 enabled
SELinuxfs mount:                /sys/fs/selinux
SELinux root directory:         /etc/selinux
Loaded policy name:             targeted
Current mode:                   permissive
Mode from config file:          permissive
Policy MLS status:              enabled
Policy deny_unknown status:     allowed
Memory protection checking:     actual (secure)
Max kernel policy version:      31

Doug Whitfield at 2021-02-09T16:14:00Z

I can only think of this "Solving computer problems 101" solution: https://www.youtube.com/watch?v=rksCTVFtjM4

It won't solve your problem but it will make you laugh. ;-)

EVAnaRkISTO@DM at 2021-02-10T11:07:54Z