Error Code 502 [Whoops, GitLab is taking too much time to respond.]

I think my upgradation is not completed. i was trying to upgrade the Gitlab CE from 10 to 11. during the upgradation getting the error also alertmanager is not running. when i trying to open the url then i am getting the error code 502 & Whoops, GitLab is taking too much time to respond.

Please help to resolve the problem.


Today i updated Gitlab CE and got same issue.
I have only 2GB or ram. Current system requirements says you need minimum 4GB or RAM.
So i increase Virtual Memory on my box.
Then restarted my box! Now everything working fine.

I have 8 GB memory and almost 4.4 GB is free. i think some wrong version i have installed. i need to downgrade the version.
Please help us to downgrade the Gitlab CE version 11 to 10.

friends@Msr-NewGitServer:~$ free -h
total used free shared buffers cached
Mem: 7.7G 3.3G 4.4G 90M 288M 2.2G
-/+ buffers/cache: 796M 6.9G
Swap: 0B 0B 0B