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add pkg/httpmetrics to export common HTTP metrics (#39)
Draft while we discuss whether this is a huge dependency bomb that should be split into a separate module. Signed-off-by: Jason Hall <[email protected]>
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,199 @@ | ||
| package httpmetrics | ||
|
|
||
| import ( | ||
| "context" | ||
| "fmt" | ||
| "log" | ||
| "log/slog" | ||
| "net/http" | ||
| "net/http/pprof" | ||
| "strconv" | ||
| "time" | ||
|
|
||
| "github.com/kelseyhightower/envconfig" | ||
| "github.com/prometheus/client_golang/prometheus" | ||
| "github.com/prometheus/client_golang/prometheus/promauto" | ||
| "github.com/prometheus/client_golang/prometheus/promhttp" | ||
| "go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp" | ||
| "go.opentelemetry.io/otel" | ||
| "go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracehttp" | ||
| "go.opentelemetry.io/otel/propagation" | ||
| "go.opentelemetry.io/otel/sdk/resource" | ||
| "go.opentelemetry.io/otel/sdk/trace" | ||
| ) | ||
|
|
||
| // ServeMetrics serves the metrics endpoint if the METRICS_PORT env var is set. | ||
| func ServeMetrics() { | ||
| // Start the metrics server on the metrics port, if defined. | ||
| var env struct { | ||
| MetricsPort int `envconfig:"METRICS_PORT" default:"2112" required:"true"` | ||
| EnablePprof bool `envconfig:"ENABLE_PPROF" default:"false" required:"true"` | ||
| } | ||
| if err := envconfig.Process("", &env); err != nil { | ||
| slog.Error("Failed to process environment variables", "error", err) | ||
| return | ||
| } | ||
| mux := http.NewServeMux() | ||
| mux.Handle("/metrics", promhttp.Handler()) | ||
| srv := &http.Server{ | ||
| Addr: fmt.Sprintf(":%d", env.MetricsPort), | ||
| Handler: mux, | ||
| ReadHeaderTimeout: 10 * time.Second, | ||
| } | ||
|
|
||
| if env.EnablePprof { | ||
| // pprof handles | ||
| mux.HandleFunc("/debug/pprof/", pprof.Index) | ||
| mux.HandleFunc("/debug/pprof/cmdline", pprof.Cmdline) | ||
| mux.HandleFunc("/debug/pprof/profile", pprof.Profile) | ||
| mux.HandleFunc("/debug/pprof/symbol", pprof.Symbol) | ||
| mux.HandleFunc("/debug/pprof/trace", pprof.Trace) | ||
| mux.Handle("/debug/pprof/allocs", pprof.Handler("allocs")) | ||
| mux.Handle("/debug/pprof/block", pprof.Handler("block")) | ||
| mux.Handle("/debug/pprof/goroutine", pprof.Handler("goroutine")) | ||
| mux.Handle("/debug/pprof/heap", pprof.Handler("heap")) | ||
| mux.Handle("/debug/pprof/mutex", pprof.Handler("mutex")) | ||
| mux.Handle("/debug/pprof/threadcreate", pprof.Handler("threadcreate")) | ||
| log.Println("registering handle for /debug/pprof") | ||
| } | ||
|
|
||
| if err := srv.ListenAndServe(); err != nil { | ||
| slog.Error("listen and serve for http /metrics", "error", err) | ||
| } | ||
| } | ||
|
|
||
| var ( | ||
| inFlightGauge = promauto.NewGaugeVec( | ||
| prometheus.GaugeOpts{ | ||
| Name: "http_inflight_requests", | ||
| Help: "A gauge of requests currently being served by the wrapped handler.", | ||
| }, | ||
| []string{"handler", "service_name", "configuration_name", "revision_name"}, | ||
| ) | ||
| duration = promauto.NewHistogramVec( | ||
| prometheus.HistogramOpts{ | ||
| Name: "http_request_duration_seconds", | ||
| Help: "A histogram of latencies for requests.", | ||
| // TODO: tweak bucket values based on real usage. | ||
| Buckets: []float64{.25, .5, 1, 2.5, 5, 10}, | ||
| }, | ||
| []string{"handler", "method", "service_name", "configuration_name", "revision_name"}, | ||
| ) | ||
| responseSize = promauto.NewHistogramVec( | ||
| prometheus.HistogramOpts{ | ||
| Name: "http_response_size_bytes", | ||
| Help: "A histogram of response sizes for requests.", | ||
| // TODO: tweak bucket values based on real usage. | ||
| Buckets: []float64{200, 500, 900, 1500}, | ||
| }, | ||
| []string{"handler", "method", "service_name", "configuration_name", "revision_name"}, | ||
| ) | ||
| counter = promauto.NewCounterVec( | ||
| prometheus.CounterOpts{ | ||
| Name: "http_request_status", | ||
| Help: "The number of processed events by response code", | ||
| }, | ||
| []string{"handler", "method", "code", "service_name", "configuration_name", "revision_name", "ce_type"}, | ||
| ) | ||
| ) | ||
|
|
||
| // https://cloud.google.com/run/docs/container-contract#services-env-vars | ||
| var env struct { | ||
| KnativeServiceName string `envconfig:"K_SERVICE" default:"unknown"` | ||
| KnativeConfigurationName string `envconfig:"K_CONFIGURATION" default:"unknown"` | ||
| KnativeRevisionName string `envconfig:"K_REVISION" default:"unknown"` | ||
| } | ||
|
|
||
| func init() { | ||
| if err := envconfig.Process("", &env); err != nil { | ||
| slog.Warn("Failed to process environment variables", "error", err) | ||
| } | ||
| } | ||
|
|
||
| // Handler wraps a given http handler in standard metrics handlers. | ||
| func Handler(name string, handler http.Handler) http.Handler { | ||
| labels := prometheus.Labels{ | ||
| "handler": name, | ||
| "service_name": env.KnativeServiceName, | ||
| "configuration_name": env.KnativeConfigurationName, | ||
| "revision_name": env.KnativeRevisionName, | ||
| } | ||
| return promhttp.InstrumentHandlerInFlight( | ||
| inFlightGauge.With(labels), | ||
| promhttp.InstrumentHandlerDuration( | ||
| duration.MustCurryWith(labels), | ||
| instrumentHandlerCounter( | ||
| counter.MustCurryWith(labels), | ||
| promhttp.InstrumentHandlerResponseSize( | ||
| responseSize.MustCurryWith(labels), | ||
| otelhttp.NewHandler(handler, ""), | ||
| ), | ||
| ), | ||
| ), | ||
| ) | ||
| } | ||
|
|
||
| // Handler wraps a given http handler func in standard metrics handlers. | ||
| func HandlerFunc(name string, f func(http.ResponseWriter, *http.Request)) http.HandlerFunc { | ||
| return Handler(name, http.HandlerFunc(f)).ServeHTTP | ||
| } | ||
|
|
||
| // Fractions >= 1 will always sample. Fractions < 0 are treated as zero. To | ||
| // respect the parent trace's `SampledFlag`, the `TraceIDRatioBased` sampler | ||
| // should be used as a delegate of a `Parent` sampler. | ||
| // | ||
| // Expected usage: | ||
| // | ||
| // defer metrics.SetupTracer(ctx)() | ||
| func SetupTracer(ctx context.Context) func() { | ||
| traceExporter, err := otlptracehttp.New(ctx) | ||
| if err != nil { | ||
| log.Panicf("SetupTracer() = %v", err) | ||
| } | ||
| bsp := trace.NewBatchSpanProcessor(traceExporter) | ||
| res := resource.Default() | ||
|
|
||
| tp := trace.NewTracerProvider( | ||
| trace.WithResource(res), | ||
| trace.WithSpanProcessor(bsp), | ||
| ) | ||
| otel.SetTracerProvider(tp) | ||
|
|
||
| prp := propagation.NewCompositeTextMapPropagator( | ||
| propagation.TraceContext{}, | ||
| propagation.Baggage{}, | ||
| ) | ||
| otel.SetTextMapPropagator(prp) | ||
|
|
||
| return func() { | ||
| if err := tp.Shutdown(context.Background()); err != nil { | ||
| slog.Error("Error shutting down tracer provider", "error", err) | ||
| } | ||
| } | ||
| } | ||
|
|
||
| type delegator struct { | ||
| http.ResponseWriter | ||
| Status int | ||
| } | ||
|
|
||
| func (d *delegator) WriteHeader(status int) { | ||
| d.Status = status | ||
| d.ResponseWriter.WriteHeader(status) | ||
| } | ||
|
|
||
| func instrumentHandlerCounter(counter *prometheus.CounterVec, next http.Handler) http.HandlerFunc { | ||
| return func(w http.ResponseWriter, r *http.Request) { | ||
| d := &delegator{ | ||
| ResponseWriter: w, | ||
| Status: 200, | ||
| } | ||
|
|
||
| next.ServeHTTP(d, r) | ||
| counter.With(prometheus.Labels{ | ||
| "method": r.Method, | ||
| "code": strconv.Itoa(d.Status), | ||
| "ce_type": r.Header.Get(CeTypeHeader), | ||
| }).Inc() | ||
| } | ||
| } |
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