Gitlab CE 8.11.7 Gitlab-rake issue

I’m working with gitlab ce 8.11.7 from past one month in starting days it worked fine.
But now as I have scheduled cron job for taking complete backup of gitlab server everyday. After running gitlab-rake command to take backup my gitlab server is throwing 502 error.
Though all services are up but still it is throwing 502 error.

I think your are lost. We are not GitLab.