Middleware registers the http_request_duration_seconds histogram metric with registry and returns a middleware that emits a request_duration_seconds metric on every request.

NewCollector creates a Collector.

NewHandler creates a new http.Handler that handles 'GET /metrics'.

NewRegistry creates a new prometheus.Registry and registers common collectors and metrics.

Collector implements the prometheus.Collector interface.

Metric is a container for a count metric and its related labels.