When I configure GitLab to use a non https url for GitLab CI, it seems to work fine. But if I try to set it up using https both gitlab and gitlab ci become unreachable. My Gitlab itself is set up with https and works fine. Any ideas? All I have tried is modifying gitlab.rb and updated the gitlab_ci_url to use the https url, and then I re-configured.
Solution
GitLab CI expects ssl certificates just like GitLab if you enable https. Put certs named <your_url>.key and <your_url>.cert into the ssl/ folder in /etc/gitlab.