Blocked by arl/statsviz#118.

What should be done?

Our debug HTTP handler exposes Prometheus metrics on /debug/metrics and Statsviz graphs on /debug/graphs. But graphs show only Go runtime metrics, not our metrics. Since version v0.6 there is a way to add graphs for user metrics. We should add some basic graphs for some metrics in prometheus.DefaultGatherer that could be expanded later.

Where?

See references to this issue.

Definition of Done

• some basic graphs added and work;
• spot refactorings done.