Initializes the Global MetricsEngine used throughout Agent Currently, we use the Prometheus Global Default Registerer, which also collecs basic Go application metrics that we use (like memory usage).

A factory method that enables various MetricsClients to be created.

We create a MetricsClient for all managed APIs (APIs for which we will collect metrics).

Function called during Agent start up to expose metrics on a local endpoint.

Maintained list of APIs for which we collect metrics.

A GenericMetricsClient records 3 metrics: 1) A Prometheus summary vector representing call durations for different API calls 2) A durations guage vector that updates the last recorded duration for the API call allowing for a time series view in the Prometheus browser 3) A counter vector that increments call counts for each API call The outstandingCalls map allows Fired CallStarts to be matched with Fired CallEnds.

MetricsClient defines the behavior for any Client that uses the MetricsEngine_ interface to collect metrics for Prometheus.

MetricsEngine_ is an interface that drives metric collection over all existing MetricsClients.