var DefaultServerMetrics … var UnaryServerInterceptor … var StreamServerInterceptor … func init() { … } // Register takes a gRPC server and pre-initializes all counters to 0. This // allows for easier monitoring in Prometheus (no missing metrics), and should // be called *after* all services have been registered with the server. This // function acts on the DefaultServerMetrics variable. func Register(server *grpc.Server) { … } // EnableHandlingTimeHistogram turns on recording of handling time // of RPCs. Histogram metrics can be very expensive for Prometheus // to retain and query. This function acts on the DefaultServerMetrics // variable and the default Prometheus metrics registry. func EnableHandlingTimeHistogram(opts ...HistogramOption) { … }