GitLab has memory leaks. These memory leaks manifest themselves in long-running processes, such as Unicorn workers. (The Unicorn master process is not known to leak memory, probably because it does not handle user requests.)
To make these memory leaks manageable, GitLab comes with the unicorn-worker-killer gem. This gem monkey-patches the Unicorn workers to do a memory self-check after every 16 requests. If the memory of the Unicorn worker exceeds a pre-set limit then the worker process exits. *
I know this is a Rails issue, but I cannot believe this is still a problem. I remember when the RoR folks blamed the Rails memory leaks on Zed, and Mongrel, more than a decade ago. They were obviously incorrect. Did the community simply give up on fixing the problem?
* https://docs.gitlab.com/ee/administration/operations/unicorn...