package caddyhttp import ( "context" "net/http" "strconv" "sync" "time" "github.com/prometheus/client_golang/prometheus" "github.com/prometheus/client_golang/prometheus/promauto" ) var httpMetrics = struct { init sync.Once requestInFlight *prometheus.GaugeVec requestCount *prometheus.CounterVec requestErrors *prometheus.CounterVec requestDuration *prometheus.HistogramVec requestSize *prometheus.HistogramVec responseSize *prometheus.HistogramVec responseDuration *prometheus.HistogramVec }{ init: sync.Once{}, } func initHTTPMetrics() { const ns, sub = "caddy", "http" basicLabels := []string{"server", "handler"} httpMetrics.requestInFlight = promauto.NewGaugeVec(prometheus.GaugeOpts{ Namespace: ns, Subsystem: sub, Name: "requests_in_flight", Help: "Number of requests currently handled by this server.", }, basicLabels) httpMetrics.requestErrors = promauto.NewCounterVec(prometheus.CounterOpts{ Namespace: ns, Subsystem: sub, Name: "request_errors_total", Help: "Number of requests resulting in middleware errors.", }, basicLabels) httpMetrics.requestCount = promauto.NewCounterVec(prometheus.CounterOpts{ Namespace: ns, Subsystem: sub, Name: "requests_total", Help: "Counter of HTTP(S) requests made.", }, basicLabels) // TODO: allow these to be customized in the config durationBuckets := prometheus.DefBuckets sizeBuckets := prometheus.ExponentialBuckets(256, 4, 8) httpLabels := []string{"server", "handler", "code", "method"} httpMetrics.requestDuration = promauto.NewHistogramVec(prometheus.HistogramOpts{ Namespace: ns, Subsystem: sub, Name: "request_duration_seconds", Help: "Histogram of round-trip request durations.", Buckets: durationBuckets, }, httpLabels) httpMetrics.requestSize = promauto.NewHistogramVec(prometheus.HistogramOpts{ Namespace: ns, Subsystem: sub, Name: "request_size_bytes", Help: "Total size of the request. Includes body", Buckets: sizeBuckets, }, httpLabels) httpMetrics.responseSize = promauto.NewHistogramVec(prometheus.HistogramOpts{ Namespace: ns, Subsystem: sub, Name: "response_size_bytes", Help: "Size of the returned response.", Buckets: sizeBuckets, }, httpLabels) httpMetrics.responseDuration = promauto.NewHistogramVec(prometheus.HistogramOpts{ Namespace: ns, Subsystem: sub, Name: "response_duration_seconds", Help: "Histogram of times to first byte in response bodies.", Buckets: durationBuckets, }, httpLabels) } // serverNameFromContext extracts the current server name from the context. // Returns "UNKNOWN" if none is available (should probably never happen). func serverNameFromContext(ctx context.Context) string { srv, ok := ctx.Value(ServerCtxKey).(*Server) if !ok || srv == nil || srv.name == "" { return "UNKNOWN" } return srv.name } type metricsInstrumentedHandler struct { handler string mh MiddlewareHandler } func newMetricsInstrumentedHandler(handler string, mh MiddlewareHandler) *metricsInstrumentedHandler { httpMetrics.init.Do(func() { initHTTPMetrics() }) return &metricsInstrumentedHandler{handler, mh} } func (h *metricsInstrumentedHandler) ServeHTTP(w http.ResponseWriter, r *http.Request, next Handler) error { server := serverNameFromContext(r.Context()) labels := prometheus.Labels{"server": server, "handler": h.handler} statusLabels := prometheus.Labels{"server": server, "handler": h.handler, "method": r.Method, "code": ""} inFlight := httpMetrics.requestInFlight.With(labels) inFlight.Inc() defer inFlight.Dec() start := time.Now() // This is a _bit_ of a hack - it depends on the ShouldBufferFunc always // being called when the headers are written. // Effectively the same behaviour as promhttp.InstrumentHandlerTimeToWriteHeader. writeHeaderRecorder := ShouldBufferFunc(func(status int, header http.Header) bool { statusLabels["code"] = sanitizeCode(status) ttfb := time.Since(start).Seconds() httpMetrics.responseDuration.With(statusLabels).Observe(ttfb) return false }) wrec := NewResponseRecorder(w, nil, writeHeaderRecorder) err := h.mh.ServeHTTP(wrec, r, next) dur := time.Since(start).Seconds() httpMetrics.requestCount.With(labels).Inc() if err != nil { httpMetrics.requestErrors.With(labels).Inc() return err } // If the code hasn't been set yet, and we didn't encounter an error, we're // probably falling through with an empty handler. if statusLabels["code"] == "" { // we still sanitize it, even though it's likely to be 0. A 200 is // returned on fallthrough so we want to reflect that. statusLabels["code"] = sanitizeCode(wrec.Status()) } httpMetrics.requestDuration.With(statusLabels).Observe(dur) httpMetrics.requestSize.With(statusLabels).Observe(float64(computeApproximateRequestSize(r))) httpMetrics.responseSize.With(statusLabels).Observe(float64(wrec.Size())) return nil } func sanitizeCode(code int) string { if code == 0 { return "200" } return strconv.Itoa(code) } // taken from https://github.com/prometheus/client_golang/blob/6007b2b5cae01203111de55f753e76d8dac1f529/prometheus/promhttp/instrument_server.go#L298 func computeApproximateRequestSize(r *http.Request) int { s := 0 if r.URL != nil { s += len(r.URL.String()) } s += len(r.Method) s += len(r.Proto) for name, values := range r.Header { s += len(name) for _, value := range values { s += len(value) } } s += len(r.Host) // N.B. r.Form and r.MultipartForm are assumed to be included in r.URL. if r.ContentLength != -1 { s += int(r.ContentLength) } return s }