After 2 years uptime, my server with gitlab (on premise) can't be reached, because the nginx proxy server can not listen to port 80.
When I restart nginx it is usually working fine for 3 days or so. Right now, this happens in a seemingly random time - 12 hours, 15 minutes, inmediatly.
This nginx server has other reverse proxy configurations to reach other web servers. Which works fine but fails when gitlab is not reachable. If I test the machine with nmap, all other servers on my networks show me port 80 open, but not nginx.
NOTE: for this to debug, I shutdown firewalls on both servers.
From the nginx Machine:
Last login: Fri Jun 12 21:24:46 2020 from 192.100.100.101
avalle@nginxsrv:~$ nmap 192.100.100.190
Starting Nmap 6.40 ( http://nmap.org ) at 2020-06-12 21:52 MDT
Nmap scan report for 192.100.100.190
Host is up (0.0050s latency).
All 1000 scanned ports on 192.100.100.190 are closed
Nmap done: 1 IP address (1 host up) scanned in 0.26 seconds
avalle@nginxsrv:~$ sudo ifdown -a && sudo ifup -a
[sudo] password for avalle:
avalle@nginxsrv:~$ nmap 192.100.100.190
Starting Nmap 6.40 ( http://nmap.org ) at 2020-06-12 21:52 MDT
Nmap scan report for 192.100.100.190
Host is up (0.00053s latency).
Not shown: 996 filtered ports
PORT STATE SERVICE
21/tcp closed ftp
22/tcp open ssh
80/tcp open http
443/tcp closed https
Nmap done: 1 IP address (1 host up) scanned in 4.96 seconds
avalle@nginxsrv:~$