Action-Cable Error: Request origin not allowed

How to Use GitLab
4

This turned out to be a layer 8 error. The proxy configuration still was wrong, I missed the ProxyPreserveHost directive, on Apache the minimum required for GitLab is:

ProxyPreserveHost on
RequestHeader add X-Forwarded-Ssl on
RequestHeader set X-Forwarded-Proto "https"

<Proxy *>
    Require all granted
</Proxy>

<Location />
    ProxyPass unix:///opt/gitlab/gitlab/tmp/sockets/gitlab-workhorse.socket|http://127.0.0.1/
    ProxyPassReverse unix:///opt/gitlab/gitlab/tmp/sockets/gitlab-workhorse.socket|http://127.0.0.1/
</Location>

<Location /-/cable>
    ProxyPass unix:///opt/gitlab/gitlab/tmp/sockets/gitlab-workhorse.socket|ws://127.0.0.1/-/cable
    ProxyPassReverse unix:///opt/gitlab/gitlab/tmp/sockets/gitlab-workhorse.socket|ws://127.0.0.1/-/cable
</Location>