From 8ec51bbede59e1fa6ac24de3607f6e7bb3e3a654 Mon Sep 17 00:00:00 2001 From: Dave Henderson Date: Thu, 17 Sep 2020 14:01:20 -0400 Subject: metrics: Initial integration of Prometheus metrics (#3709) Signed-off-by: Dave Henderson --- modules/caddyhttp/metrics.go | 195 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 195 insertions(+) create mode 100644 modules/caddyhttp/metrics.go (limited to 'modules/caddyhttp/metrics.go') diff --git a/modules/caddyhttp/metrics.go b/modules/caddyhttp/metrics.go new file mode 100644 index 0000000..dbf1033 --- /dev/null +++ b/modules/caddyhttp/metrics.go @@ -0,0 +1,195 @@ +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) +} + +type ctxKeyServerName struct{} + +// 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 { + srvName, ok := ctx.Value(ctxKeyServerName{}).(string) + if !ok { + return "UNKNOWN" + } + return srvName +} + +func contextWithServerName(ctx context.Context, serverName string) context.Context { + return context.WithValue(ctx, ctxKeyServerName{}, serverName) +} + +type metricsInstrumentedHandler struct { + labels prometheus.Labels + statusLabels prometheus.Labels + mh MiddlewareHandler +} + +func newMetricsInstrumentedHandler(server, handler string, mh MiddlewareHandler) *metricsInstrumentedHandler { + httpMetrics.init.Do(func() { + initHTTPMetrics() + }) + + labels := prometheus.Labels{"server": server, "handler": handler} + statusLabels := prometheus.Labels{"server": server, "handler": handler, "code": "", "method": ""} + return &metricsInstrumentedHandler{labels, statusLabels, mh} +} + +func (h *metricsInstrumentedHandler) ServeHTTP(w http.ResponseWriter, r *http.Request, next Handler) error { + inFlight := httpMetrics.requestInFlight.With(h.labels) + inFlight.Inc() + defer inFlight.Dec() + + statusLabels := prometheus.Labels{"method": r.Method} + for k, v := range h.labels { + statusLabels[k] = v + } + + 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() + observeWithExemplar(statusLabels, httpMetrics.responseDuration, ttfb) + return false + }) + wrec := NewResponseRecorder(w, nil, writeHeaderRecorder) + err := h.mh.ServeHTTP(wrec, r, next) + dur := time.Since(start).Seconds() + httpMetrics.requestCount.With(h.labels).Inc() + if err != nil { + httpMetrics.requestErrors.With(h.labels).Inc() + return err + } + + observeWithExemplar(statusLabels, httpMetrics.requestDuration, dur) + observeWithExemplar(statusLabels, httpMetrics.requestSize, float64(computeApproximateRequestSize(r))) + httpMetrics.responseSize.With(statusLabels).Observe(float64(wrec.Size())) + + return nil +} + +func observeWithExemplar(l prometheus.Labels, o *prometheus.HistogramVec, value float64) { + obs := o.With(l) + if oe, ok := obs.(prometheus.ExemplarObserver); ok { + oe.ObserveWithExemplar(value, l) + return + } + // _should_ be a noop, but here just in case... + obs.Observe(value) +} + +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 +} -- cgit v1.2.3