Replay Server

Metrics

The replay-server is configured with support for prometheus metrics which can be reported and scraped from the /metrics endpoint.

 curl http://localhost/metrics

# HELP promhttp_metric_handler_requests_in_flight Current number of scrapes being served.
# TYPE promhttp_metric_handler_requests_in_flight gauge
promhttp_metric_handler_requests_in_flight 1
# HELP promhttp_metric_handler_requests_total Total number of scrapes by HTTP status code.
# TYPE promhttp_metric_handler_requests_total counter
promhttp_metric_handler_requests_total{code="200"} 4
promhttp_metric_handler_requests_total{code="500"} 0
promhttp_metric_handler_requests_total{code="503"} 0


# HELP go_threads Number of OS threads created.
# TYPE go_threads gauge
# HELP go_gc_duration_seconds A summary of the pause duration of garbage collection cycles.
# TYPE go_gc_duration_seconds summary
go_gc_duration_seconds{quantile="0"} 0.000143874
go_gc_duration_seconds{quantile="0.25"} 0.000143874
go_gc_duration_seconds{quantile="0.5"} 0.000224583
go_gc_duration_seconds{quantile="0.75"} 0.000224583
go_gc_duration_seconds{quantile="1"} 0.000224583
go_gc_duration_seconds_sum 0.000368457
go_gc_duration_seconds_count 2
# HELP go_goroutines Number of goroutines that currently exist.
# TYPE go_goroutines gauge
go_goroutines 10
# HELP go_info Information about the Go environment.
# TYPE go_info gauge
go_info{version="go1.20.6"} 1

Creating New Metrics

You can create custom metrics using a simialar pattern as the following example which will track a success metric counter for the health check endpoint.

var (
	healthCheckCount = promauto.NewCounterVec(prometheus.CounterOpts{
		Name: "health_check_count_total",
		Help: "Total count of health checks",
	}, []string{"status"})
)

func (s *Server) handleHealthCheck(w http.ResponseWriter, r *http.Request, _ httprouter.Params) int {
	{%- if values.database.enabled %}
	err := s.Db.Ping()
	if err != nil {
		healthCheckCount.WithLabelValues("failure").Inc()
		w.WriteHeader(http.StatusInternalServerError)
		return http.StatusInternalServerError
	}
	{% endif %}
	healthCheckCount.WithLabelValues("success").Inc()
	w.WriteHeader(http.StatusOK)
	return http.StatusOK
}