metrics.go

package gateway

import (
	"net"
	"net/http"
	"time"

	ocprom "contrib.go.opencensus.io/exporter/prometheus"
	"github.com/prometheus/client_golang/prometheus"
	"github.com/prometheus/client_golang/prometheus/promhttp"
	"go.opencensus.io/stats/view"
	"go.opencensus.io/zpages"
)

// MetricsScrapingOption adds the scraping endpoint which Prometheus uses to fetch metrics.
func MetricsScrapingOption(path string) ServeOption {
	return func(_ API, _ *GatewayConfig, _ net.Listener, mux *http.ServeMux) (*http.ServeMux, error) {
		mux.Handle(path, promhttp.HandlerFor(prometheus.DefaultGatherer, promhttp.HandlerOpts{}))
		return mux, nil
	}
}

// This adds collection of OpenCensus metrics
func MetricsOpenCensusCollectionOption() ServeOption {
	return func(_ API, _ *GatewayConfig, _ net.Listener, mux *http.ServeMux) (*http.ServeMux, error) {
		log.Info("Init OpenCensus")

		promRegistry := prometheus.NewRegistry()
		pe, err := ocprom.NewExporter(ocprom.Options{
			Namespace: "ipfs_oc",
			Registry:  promRegistry,
			OnError: func(err error) {
				log.Errorw("OC ERROR", "error", err)
			},
		})
		if err != nil {
			return nil, err
		}

		// register prometheus with opencensus
		view.RegisterExporter(pe)
		view.SetReportingPeriod(2 * time.Second)

		// Construct the mux
		zpages.Handle(mux, "/debug/metrics/oc/debugz")
		mux.Handle("/debug/metrics/oc", pe)

		return mux, nil
	}
}

// MetricsCollectionOption adds collection of net/http-related metrics.
func MetricsCollectionOption(handlerName string) ServeOption {
	return func(_ API, _ *GatewayConfig, _ net.Listener, mux *http.ServeMux) (*http.ServeMux, error) {
		// Adapted from github.com/prometheus/client_golang/prometheus/http.go
		// Work around https://github.com/prometheus/client_golang/pull/311
		opts := prometheus.SummaryOpts{
			Namespace:   "ipfs",
			Subsystem:   "http",
			ConstLabels: prometheus.Labels{"handler": handlerName},
			Objectives:  map[float64]float64{0.5: 0.05, 0.9: 0.01, 0.99: 0.001},
		}

		reqCnt := prometheus.NewCounterVec(
			prometheus.CounterOpts{
				Namespace:   opts.Namespace,
				Subsystem:   opts.Subsystem,
				Name:        "requests_total",
				Help:        "Total number of HTTP requests made.",
				ConstLabels: opts.ConstLabels,
			},
			[]string{"method", "code"},
		)
		if err := prometheus.Register(reqCnt); err != nil {
			if are, ok := err.(prometheus.AlreadyRegisteredError); ok {
				reqCnt = are.ExistingCollector.(*prometheus.CounterVec)
			} else {
				return nil, err
			}
		}

		opts.Name = "request_duration_seconds"
		opts.Help = "The HTTP request latencies in seconds."
		reqDur := prometheus.NewSummaryVec(opts, nil)
		if err := prometheus.Register(reqDur); err != nil {
			if are, ok := err.(prometheus.AlreadyRegisteredError); ok {
				reqDur = are.ExistingCollector.(*prometheus.SummaryVec)
			} else {
				return nil, err
			}
		}

		opts.Name = "request_size_bytes"
		opts.Help = "The HTTP request sizes in bytes."
		reqSz := prometheus.NewSummaryVec(opts, nil)
		if err := prometheus.Register(reqSz); err != nil {
			if are, ok := err.(prometheus.AlreadyRegisteredError); ok {
				reqSz = are.ExistingCollector.(*prometheus.SummaryVec)
			} else {
				return nil, err
			}
		}

		opts.Name = "response_size_bytes"
		opts.Help = "The HTTP response sizes in bytes."
		resSz := prometheus.NewSummaryVec(opts, nil)
		if err := prometheus.Register(resSz); err != nil {
			if are, ok := err.(prometheus.AlreadyRegisteredError); ok {
				resSz = are.ExistingCollector.(*prometheus.SummaryVec)
			} else {
				return nil, err
			}
		}

		// Construct the mux
		childMux := http.NewServeMux()
		var promMux http.Handler = childMux
		promMux = promhttp.InstrumentHandlerResponseSize(resSz, promMux)
		promMux = promhttp.InstrumentHandlerRequestSize(reqSz, promMux)
		promMux = promhttp.InstrumentHandlerDuration(reqDur, promMux)
		promMux = promhttp.InstrumentHandlerCounter(reqCnt, promMux)
		mux.Handle("/", promMux)

		return childMux, nil
	}
}

/*
var (
	peersTotalMetric = prometheus.NewDesc(
		prometheus.BuildFQName("ipfs", "p2p", "peers_total"),
		"Number of connected peers",
		[]string{"transport"},
		nil,
	)
)
*/