Create and package a Prometheus exporter based on the existing Diamond collector
I'm reopening this. With the current exporter, the metrics go through the following chain:
jmx -> jolokia -> prometheus-wdqs-updater-exporter -> prometheus
Since all metrics we collect are available via JMX, we can do simpler:
jmx -> prometheus-jmx-exporter -> prometheus
This has the added advantage of publishing the standard JVM metrics in a standard way.
Jolokia agent is not loaded anymore with https://gerrit.wikimedia.org/r/405907. We could also remove all references to jolokia, remove it from the packaging. This would make sense as the monitoring tools should be a deployment concern, and not part of the application itself. That being said, we might have other users of wdqs-updater who rely on jolokia already. @Smalyshev what do you think?
I think if somebody needs jolokia for their own reporting, they can add it back through the options. Jolokia is not part of the API, it's a monitoring thing, so I don't think we need to keep it around if we don't need it.