Instrument Unicorn with Ruby exporter
Now that we have added our Ruby exporter to GitLab, we need to start to instrument GitLab to use it and begin exporting metrics. One of the ones we should start with, is to monitor the number of connections it is currently handling. https://gitlab.com/gitlab-com/infrastructure/issues/1955
Metrics that should be relatively easy to extract include:
- counter incremented when rack starts processing incoming connection
- histogram of time spent processing the request
Additionally Raindrops looks like an option to access stats of unix or tcp socket used by Unicorn.