feat: Add Prometheus metrics and health endpoints

api/api.go

@@ -5,6 +5,8 @@ import (
 	"time"
 
 	"github.com/patrickmn/go-cache"
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
 	"github.com/sirupsen/logrus"
 	"github.com/yukimochi/Activity-Relay/models"
 	"github.com/yukimochi/machinery-v1/v1"
@@ -24,6 +26,8 @@ var (
 	ActorCache      *cache.Cache
 	MachineryServer *machinery.Server
 	RelayState      models.RelayState
+
+	metrics *defaultMetrics
 )
 
 func Entrypoint(g *models.RelayConfig, v string) error {
@@ -32,6 +36,9 @@ func Entrypoint(g *models.RelayConfig, v string) error {
 	version = v
 	GlobalConfig = g
 
+	// Initialize the metrics
+	metrics = newDefaultMetrics(prometheus.DefaultRegisterer, nil, nil)
+
 	err = initialize(GlobalConfig)
 	if err != nil {
 		return err
@@ -70,11 +77,31 @@ func initialize(globalConfig *models.RelayConfig) error {
 }
 
 func handlersRegister() {
-	http.HandleFunc("/.well-known/nodeinfo", handleNodeinfoLink)
-	http.HandleFunc("/.well-known/webfinger", handleWebfinger)
-	http.HandleFunc("/nodeinfo/2.1", handleNodeinfo)
-	http.HandleFunc("/actor", handleRelayActor)
-	http.HandleFunc("/inbox", func(w http.ResponseWriter, r *http.Request) {
+	// Register the Prometheus metrics endpoint
+	http.Handle("/metrics", promhttp.Handler())
+
+	// Register the new health and readiness endpoints
+	http.Handle("/-/healthy", metrics.MetricsMiddleware(http.HandlerFunc(handleHealthy)))
+	http.Handle("/-/ready", metrics.MetricsMiddleware(http.HandlerFunc(handleReady)))
+
+	// Wrap handlers with the metrics middleware, preserving the URL path
+	http.Handle("/.well-known/nodeinfo", metrics.MetricsMiddleware(http.HandlerFunc(handleNodeinfoLink)))
+	http.Handle("/.well-known/webfinger", metrics.MetricsMiddleware(http.HandlerFunc(handleWebfinger)))
+	http.Handle("/nodeinfo/2.1", metrics.MetricsMiddleware(http.HandlerFunc(handleNodeinfo)))
+	http.Handle("/actor", metrics.MetricsMiddleware(http.HandlerFunc(handleRelayActor)))
+	http.Handle("/inbox", metrics.MetricsMiddleware(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		handleInbox(w, r, decodeActivity)
-	})
+	})))
+}
+
+// handleHealthy returns a health status message
+func handleHealthy(w http.ResponseWriter, r *http.Request) {
+	w.WriteHeader(http.StatusOK)
+	w.Write([]byte("ActivityRelay is Healthy."))
+}
+
+// handleReady returns a readiness status message
+func handleReady(w http.ResponseWriter, r *http.Request) {
+	w.WriteHeader(http.StatusOK)
+	w.Write([]byte("ActivityRelay is Ready."))
 }

api/metrics.go

@@ -0,0 +1,129 @@
+package api
+
+import (
+	"net/http"
+	"strconv"
+	"time"
+
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promauto"
+)
+
+type defaultMetrics struct {
+	requestDuration      *prometheus.HistogramVec
+	requestSize          *prometheus.HistogramVec
+	requestsTotal        *prometheus.CounterVec
+	responseSize         *prometheus.HistogramVec
+	inflightHTTPRequests *prometheus.GaugeVec
+}
+
+func newDefaultMetrics(reg prometheus.Registerer, durationBuckets []float64, extraLabels []string) *defaultMetrics {
+	if durationBuckets == nil {
+		durationBuckets = []float64{0.001, 0.01, 0.1, 0.3, 0.6, 1, 3, 6, 9, 20, 30, 60, 90, 120, 240, 360, 720}
+	}
+
+	bytesBuckets := prometheus.ExponentialBuckets(64, 2, 10)
+	bucketFactor := 1.1
+	maxBuckets := uint32(100)
+
+	return &defaultMetrics{
+		requestDuration: promauto.With(reg).NewHistogramVec(
+			prometheus.HistogramOpts{
+				Name:                           "http_request_duration_seconds",
+				Help:                           "Tracks the latencies for HTTP requests.",
+				Buckets:                        durationBuckets,
+				NativeHistogramBucketFactor:    bucketFactor,
+				NativeHistogramMaxBucketNumber: maxBuckets,
+			},
+			append([]string{"code", "handler", "method"}, extraLabels...),
+		),
+
+		requestSize: promauto.With(reg).NewHistogramVec(
+			prometheus.HistogramOpts{
+				Name:                           "http_request_size_bytes",
+				Help:                           "Tracks the size of HTTP requests.",
+				Buckets:                        bytesBuckets,
+				NativeHistogramBucketFactor:    bucketFactor,
+				NativeHistogramMaxBucketNumber: maxBuckets,
+			},
+			append([]string{"code", "handler", "method"}, extraLabels...),
+		),
+
+		requestsTotal: promauto.With(reg).NewCounterVec(
+			prometheus.CounterOpts{
+				Name: "http_requests_total",
+				Help: "Tracks the number of HTTP requests.",
+			},
+			append([]string{"code", "handler", "method"}, extraLabels...),
+		),
+
+		responseSize: promauto.With(reg).NewHistogramVec(
+			prometheus.HistogramOpts{
+				Name:                           "http_response_size_bytes",
+				Help:                           "Tracks the size of HTTP responses.",
+				Buckets:                        bytesBuckets,
+				NativeHistogramBucketFactor:    bucketFactor,
+				NativeHistogramMaxBucketNumber: maxBuckets,
+			},
+			append([]string{"code", "handler", "method"}, extraLabels...),
+		),
+
+		inflightHTTPRequests: promauto.With(reg).NewGaugeVec(
+			prometheus.GaugeOpts{
+				Name: "http_inflight_requests",
+				Help: "Current number of HTTP requests the handler is responding to.",
+			},
+			append([]string{"handler", "method"}, extraLabels...),
+		),
+	}
+}
+
+func (m *defaultMetrics) MetricsMiddleware(next http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		start := time.Now()
+
+		// Extract the request path and method
+		requestPath := r.URL.Path
+
+		// Increment inflight requests gauge
+		m.inflightHTTPRequests.WithLabelValues(requestPath, r.Method).Inc()
+		defer m.inflightHTTPRequests.WithLabelValues(requestPath, r.Method).Dec()
+
+		// Capture the response size
+		rw := &responseWriter{w: w}
+		next.ServeHTTP(rw, r)
+
+		duration := time.Since(start).Seconds()
+		statusCode := strconv.Itoa(rw.statusCode)
+
+		// Observe metrics
+		m.requestDuration.WithLabelValues(statusCode, requestPath, r.Method).Observe(duration)
+		m.requestSize.WithLabelValues(statusCode, requestPath, r.Method).Observe(float64(r.ContentLength))
+		m.requestsTotal.WithLabelValues(statusCode, requestPath, r.Method).Inc()
+		m.responseSize.WithLabelValues(statusCode, requestPath, r.Method).Observe(float64(rw.size))
+	})
+}
+
+type responseWriter struct {
+	w          http.ResponseWriter
+	statusCode int
+	size       int
+}
+
+func (rw *responseWriter) Header() http.Header {
+	return rw.w.Header()
+}
+
+func (rw *responseWriter) Write(b []byte) (int, error) {
+	if rw.statusCode == 0 {
+		rw.statusCode = http.StatusOK
+	}
+	size, err := rw.w.Write(b)
+	rw.size += size
+	return size, err
+}
+
+func (rw *responseWriter) WriteHeader(statusCode int) {
+	rw.w.WriteHeader(statusCode)
+	rw.statusCode = statusCode
+}

go.mod

@@ -16,7 +16,8 @@ require (
 
 require (
 	github.com/RichardKnop/logging v0.0.0-20190827224416-1a693bdd4fae // indirect
-	github.com/cespare/xxhash/v2 v2.2.0 // indirect
+	github.com/beorn7/perks v1.0.1 // indirect
+	github.com/cespare/xxhash/v2 v2.3.0 // indirect
 	github.com/dgryski/go-rendezvous v0.0.0-20200823014737-9f7001d12a5f // indirect
 	github.com/fsnotify/fsnotify v1.7.0 // indirect
 	github.com/go-redis/redis/v8 v8.11.5 // indirect
@@ -27,11 +28,17 @@ require (
 	github.com/hashicorp/hcl v1.0.0 // indirect
 	github.com/inconshreveable/mousetrap v1.1.0 // indirect
 	github.com/kelseyhightower/envconfig v1.4.0 // indirect
+	github.com/klauspost/compress v1.17.9 // indirect
 	github.com/magiconair/properties v1.8.7 // indirect
 	github.com/mitchellh/mapstructure v1.5.0 // indirect
+	github.com/munnerz/goautoneg v0.0.0-20191010083416-a7dc8b61c822 // indirect
 	github.com/opentracing/opentracing-go v1.2.0 // indirect
 	github.com/pelletier/go-toml/v2 v2.2.2 // indirect
 	github.com/pkg/errors v0.9.1 // indirect
+	github.com/prometheus/client_golang v1.20.2 // indirect
+	github.com/prometheus/client_model v0.6.1 // indirect
+	github.com/prometheus/common v0.55.0 // indirect
+	github.com/prometheus/procfs v0.15.1 // indirect
 	github.com/rabbitmq/amqp091-go v1.10.0 // indirect
 	github.com/robfig/cron/v3 v3.0.1 // indirect
 	github.com/sagikazarmark/locafero v0.4.0 // indirect
@@ -45,8 +52,9 @@ require (
 	go.uber.org/multierr v1.9.0 // indirect
 	golang.org/x/crypto v0.21.0 // indirect
 	golang.org/x/exp v0.0.0-20230905200255-921286631fa9 // indirect
-	golang.org/x/sys v0.18.0 // indirect
-	golang.org/x/text v0.14.0 // indirect
+	golang.org/x/sys v0.22.0 // indirect
+	golang.org/x/text v0.16.0 // indirect
+	google.golang.org/protobuf v1.34.2 // indirect
 	gopkg.in/ini.v1 v1.67.0 // indirect
 	gopkg.in/yaml.v2 v2.4.0 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect

go.sum

@@ -2,12 +2,16 @@ github.com/RichardKnop/logging v0.0.0-20190827224416-1a693bdd4fae h1:DcFpTQBYQ9C
 github.com/RichardKnop/logging v0.0.0-20190827224416-1a693bdd4fae/go.mod h1:rJJ84PyA/Wlmw1hO+xTzV2wsSUon6J5ktg0g8BF2PuU=
 github.com/Songmu/go-httpdate v1.0.0 h1:39S00oyg9q+kMso2ahhK4pvD4EXk4zQWzt/AMqGlH3o=
 github.com/Songmu/go-httpdate v1.0.0/go.mod h1:QPvdlIAR7M8UtklJx5CMOOCIq7hbx2QdxyEPvTF5QVs=
+github.com/beorn7/perks v1.0.1 h1:VlbKKnNfV8bJzeqoa4cOKqO6bYr3WgKZxO8Z16+hsOM=
+github.com/beorn7/perks v1.0.1/go.mod h1:G2ZrVWU2WbWT9wwq4/hrbKbnv/1ERSJQ0ibhJ6rlkpw=
 github.com/bsm/ginkgo/v2 v2.12.0 h1:Ny8MWAHyOepLGlLKYmXG4IEkioBysk6GpaRTLC8zwWs=
 github.com/bsm/ginkgo/v2 v2.12.0/go.mod h1:SwYbGRRDovPVboqFv0tPTcG1sN61LM1Z4ARdbAV9g4c=
 github.com/bsm/gomega v1.27.10 h1:yeMWxP2pV2fG3FgAODIY8EiRE3dy0aeFYt4l7wh6yKA=
 github.com/bsm/gomega v1.27.10/go.mod h1:JyEr/xRbxbtgWNi8tIEVPUYZ5Dzef52k01W3YH0H+O0=
 github.com/cespare/xxhash/v2 v2.2.0 h1:DC2CZ1Ep5Y4k3ZQ899DldepgrayRUGE6BBZ/cd9Cj44=
 github.com/cespare/xxhash/v2 v2.2.0/go.mod h1:VGX0DQ3Q6kWi7AoAeZDth3/j3BFtOZR5XLFGgcrjCOs=
+github.com/cespare/xxhash/v2 v2.3.0 h1:UL815xU9SqsFlibzuggzjXhog7bL6oX9BbNZnL2UFvs=
+github.com/cespare/xxhash/v2 v2.3.0/go.mod h1:VGX0DQ3Q6kWi7AoAeZDth3/j3BFtOZR5XLFGgcrjCOs=
 github.com/cpuguy83/go-md2man/v2 v2.0.4/go.mod h1:tgQtvFlXSQOSOSIRvRPT7W67SCa46tRHOmNcaadrF8o=
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
@@ -46,6 +50,8 @@ github.com/inconshreveable/mousetrap v1.1.0 h1:wN+x4NVGpMsO7ErUn/mUI3vEoE6Jt13X2
 github.com/inconshreveable/mousetrap v1.1.0/go.mod h1:vpF70FUmC8bwa3OWnCshd2FqLfsEA9PFc4w1p2J65bw=
 github.com/kelseyhightower/envconfig v1.4.0 h1:Im6hONhd3pLkfDFsbRgu68RDNkGF1r3dvMUtDTo2cv8=
 github.com/kelseyhightower/envconfig v1.4.0/go.mod h1:cccZRl6mQpaq41TPp5QxidR+Sa3axMbJDNb//FQX6Gg=
+github.com/klauspost/compress v1.17.9 h1:6KIumPrER1LHsvBVuDa0r5xaG0Es51mhhB9BQB2qeMA=
+github.com/klauspost/compress v1.17.9/go.mod h1:Di0epgTjJY877eYKx5yC51cX2A2Vl2ibi7bDH9ttBbw=
 github.com/kr/pretty v0.3.1 h1:flRD4NNwYAUpkphVc1HcthR4KEIFJ65n8Mw5qdRn3LE=
 github.com/kr/pretty v0.3.1/go.mod h1:hoEshYVHaxMs3cyo3Yncou5ZscifuDolrwPKZanG3xk=
 github.com/kr/text v0.2.0 h1:5Nx0Ya0ZqY2ygV366QzturHI13Jq95ApcVaJBhpS+AY=
@@ -54,6 +60,8 @@ github.com/magiconair/properties v1.8.7 h1:IeQXZAiQcpL9mgcAe1Nu6cX9LLw6ExEHKjN0V
 github.com/magiconair/properties v1.8.7/go.mod h1:Dhd985XPs7jluiymwWYZ0G4Z61jb3vdS329zhj2hYo0=
 github.com/mitchellh/mapstructure v1.5.0 h1:jeMsZIYE/09sWLaz43PL7Gy6RuMjD2eJVyuac5Z2hdY=
 github.com/mitchellh/mapstructure v1.5.0/go.mod h1:bFUtVrKA4DC2yAKiSyO/QUcy7e+RRV2QTWOzhPopBRo=
+github.com/munnerz/goautoneg v0.0.0-20191010083416-a7dc8b61c822 h1:C3w9PqII01/Oq1c1nUAm88MOHcQC9l5mIlSMApZMrHA=
+github.com/munnerz/goautoneg v0.0.0-20191010083416-a7dc8b61c822/go.mod h1:+n7T8mK8HuQTcFwEeznm/DIxMOiR9yIdICNftLE1DvQ=
 github.com/nxadm/tail v1.4.8 h1:nPr65rt6Y5JFSKQO7qToXr7pePgD6Gwiw05lkbyAQTE=
 github.com/nxadm/tail v1.4.8/go.mod h1:+ncqLTQzXmGhMZNUePPaPqPvBxHAIsmXswZKocGu+AU=
 github.com/onsi/ginkgo v1.16.5 h1:8xi0RTUf59SOSfEtZMvwTvXYMzG4gV23XVHOZiXNtnE=
@@ -71,6 +79,14 @@ github.com/pkg/errors v0.9.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINE
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/pmezard/go-difflib v1.0.1-0.20181226105442-5d4384ee4fb2 h1:Jamvg5psRIccs7FGNTlIRMkT8wgtp5eCXdBlqhYGL6U=
 github.com/pmezard/go-difflib v1.0.1-0.20181226105442-5d4384ee4fb2/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/prometheus/client_golang v1.20.2 h1:5ctymQzZlyOON1666svgwn3s6IKWgfbjsejTMiXIyjg=
+github.com/prometheus/client_golang v1.20.2/go.mod h1:PIEt8X02hGcP8JWbeHyeZ53Y/jReSnHgO035n//V5WE=
+github.com/prometheus/client_model v0.6.1 h1:ZKSh/rekM+n3CeS952MLRAdFwIKqeY8b62p8ais2e9E=
+github.com/prometheus/client_model v0.6.1/go.mod h1:OrxVMOVHjw3lKMa8+x6HeMGkHMQyHDk9E3jmP2AmGiY=
+github.com/prometheus/common v0.55.0 h1:KEi6DK7lXW/m7Ig5i47x0vRzuBsHuvJdi5ee6Y3G1dc=
+github.com/prometheus/common v0.55.0/go.mod h1:2SECS4xJG1kd8XF9IcM1gMX6510RAEL65zxzNImwdc8=
+github.com/prometheus/procfs v0.15.1 h1:YagwOFzUgYfKKHX6Dr+sHT7km/hxC76UB0learggepc=
+github.com/prometheus/procfs v0.15.1/go.mod h1:fB45yRUv8NstnjriLhBQLuOUt+WW4BsoGhij/e3PBqk=
 github.com/rabbitmq/amqp091-go v1.10.0 h1:STpn5XsHlHGcecLmMFCtg7mqq0RnD+zFr4uzukfVhBw=
 github.com/rabbitmq/amqp091-go v1.10.0/go.mod h1:Hy4jKW5kQART1u+JkDTF9YYOQUHXqMuhrgxOEeS7G4o=
 github.com/redis/go-redis/v9 v9.6.1 h1:HHDteefn6ZkTtY5fGUE8tj8uy85AHk6zP7CpzIAM0y4=
@@ -140,11 +156,17 @@ golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7w
 golang.org/x/sys v0.0.0-20220715151400-c0bba94af5f8/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.18.0 h1:DBdB3niSjOA/O0blCZBqDefyWNYveAYMNF1Wum0DYQ4=
 golang.org/x/sys v0.18.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
+golang.org/x/sys v0.22.0 h1:RI27ohtqKCnwULzJLqkv897zojh5/DwS/ENaMzUOaWI=
+golang.org/x/sys v0.22.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
 golang.org/x/term v0.18.0 h1:FcHjZXDMxI8mM3nwhX9HlKop4C0YQvCVCdwYl2wOtE8=
 golang.org/x/term v0.18.0/go.mod h1:ILwASektA3OnRv7amZ1xhE/KTR+u50pbXfZ03+6Nx58=
 golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
 golang.org/x/text v0.14.0 h1:ScX5w1eTa3QqT8oi6+ziP7dTV1S2+ALU0bI+0zXKWiQ=
 golang.org/x/text v0.14.0/go.mod h1:18ZOQIKpY8NJVqYksKHtTdi31H5itFRjB5/qKTNYzSU=
+golang.org/x/text v0.16.0 h1:a94ExnEXNtEwYLGJSIUxnWoxoRz/ZcCsV63ROupILh4=
+golang.org/x/text v0.16.0/go.mod h1:GhwF1Be+LQoKShO3cGOHzqOgRrGaYc9AvblQOmPVHnI=
+google.golang.org/protobuf v1.34.2 h1:6xV6lTsCfpGD21XK49h7MhtcApnLqkfYgPcdHftf6hg=
+google.golang.org/protobuf v1.34.2/go.mod h1:qYOHts0dSfpeUzUFpOMr/WGzszTmLH+DiWniOlNbLDw=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/check.v1 v1.0.0-20190902080502-41f04d3bba15 h1:YR8cESwS4TdDjEe65xsg0ogRM/Nc3DYOhEAlW+xobZo=
 gopkg.in/check.v1 v1.0.0-20190902080502-41f04d3bba15/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=