NewMetricsEngine reads the configuration and returns the appropriate metrics engine for this instance.

DetailedMetricsEngine is a MultiMetricsEngine that preserves links to underlying metrics engines.

NilMetricsEngine implements the MetricsEngine interface where no metrics are actually captured.

MultiMetricsEngine logs metrics to multiple metrics databases The can be useful in transitioning an instance from one engine to another, you can run both in parallel to verify stats match up.