Document Sidekiq troubleshooting steps
Related to https://dev.gitlab.org/gitlab/organization/issues/802 (private).
In a recent customer issue we learned a lot about troubleshooting Sidekiq when it's stuck. We should document this because I think it will help us get to the bottom of issues faster in the future.
Things to potentially document:
- TTIN signal
- Use
perf
- Use
gdb
- Look for blocking queries in PG
cc/ @stanhu @jacobvosmaer Please provide input if you have ideas.