feat: add prometheus metrics

Dockerfile

@@ -1,4 +1,4 @@
-ARG GOLANG_VERSION=1.17
+ARG GOLANG_VERSION=1.20
 FROM golang:${GOLANG_VERSION}-bullseye as builder
 
 ARG IMAGINARY_VERSION=dev

go.mod

@@ -1,12 +1,24 @@
 module github.com/h2non/imaginary
 
-go 1.12
+go 1.20
 
 require (
-	github.com/garyburd/redigo v1.6.0 // indirect
-	github.com/h2non/bimg v1.1.7
-	github.com/h2non/filetype v1.1.0
-	github.com/hashicorp/golang-lru v0.0.0-20160813221303-0a025b7e63ad // indirect
-	github.com/rs/cors v0.0.0-20170727213201-7af7a1e09ba3
-	gopkg.in/throttled/throttled.v2 v2.0.3
+	github.com/h2non/bimg v1.1.9
+	github.com/h2non/filetype v1.1.3
+	github.com/prometheus/client_golang v1.20.3
+	github.com/rs/cors v1.11.1
+	github.com/throttled/throttled/v2 v2.12.0
+)
+
+require (
+	github.com/beorn7/perks v1.0.1 // indirect
+	github.com/cespare/xxhash/v2 v2.3.0 // indirect
+	github.com/hashicorp/golang-lru v1.0.2 // indirect
+	github.com/klauspost/compress v1.17.9 // indirect
+	github.com/munnerz/goautoneg v0.0.0-20191010083416-a7dc8b61c822 // indirect
+	github.com/prometheus/client_model v0.6.1 // indirect
+	github.com/prometheus/common v0.59.1 // indirect
+	github.com/prometheus/procfs v0.15.1 // indirect
+	golang.org/x/sys v0.25.0 // indirect
+	google.golang.org/protobuf v1.34.2 // indirect
 )

go.sum

@@ -1,12 +1,141 @@
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+golang.org/x/term v0.0.0-20210927222741-03fcf44c2211/go.mod h1:jbD1KX2456YbFQfuXm/mYQcufACuNUgVhRMnK/tPxf8=
+golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
+golang.org/x/text v0.3.2/go.mod h1:bEr9sfX3Q8Zfm5fL9x+3itogRgK3+ptLWKqgva+5dAk=
+golang.org/x/text v0.3.3/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
+golang.org/x/text v0.3.7/go.mod h1:u+2+/6zg+i71rQMx5EYifcz6MCKuco9NR6JIITiCfzQ=
+golang.org/x/text v0.3.8/go.mod h1:E6s5w1FMmriuDzIBO73fBruAKo1PCIq6d2Q6DHfQ8WQ=
+golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
+golang.org/x/tools v0.0.0-20191119224855-298f0cb1881e/go.mod h1:b+2E5dAYhXwXZwtnZ6UAqBI28+e2cm9otk0dWdXHAEo=
+golang.org/x/tools v0.1.12/go.mod h1:hNGJHUnrk76NpqgfD5Aqm5Crs+Hm0VOH/i9J2+nxYbc=
+golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
+golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
+google.golang.org/protobuf v0.0.0-20200109180630-ec00e32a8dfd/go.mod h1:DFci5gLYBciE7Vtevhsrf46CRTquxDuWsQurQQe4oz8=
+google.golang.org/protobuf v0.0.0-20200221191635-4d8936d0db64/go.mod h1:kwYJMbMJ01Woi6D6+Kah6886xMZcty6N08ah7+eCXa0=
+google.golang.org/protobuf v0.0.0-20200228230310-ab0ca4ff8a60/go.mod h1:cfTl7dwQJ+fmap5saPgwCLgHXTUD7jkjRqWcaiX5VyM=
+google.golang.org/protobuf v1.20.1-0.20200309200217-e05f789c0967/go.mod h1:A+miEFZTKqfCUM6K7xSMQL9OKL/b6hQv+e19PK+JZNE=
+google.golang.org/protobuf v1.21.0/go.mod h1:47Nbq4nVaFHyn7ilMalzfO3qCViNmqZ2kzikPIcrTAo=
+google.golang.org/protobuf v1.23.0/go.mod h1:EGpADcykh3NcUnDUJcl1+ZksZNG86OlYog2l/sGQquU=
+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/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/fsnotify.v1 v1.4.7/go.mod h1:Tz8NjZHkW78fSQdbUxIjBTcgA1z1m8ZHf0WmKUhAMys=
+gopkg.in/tomb.v1 v1.0.0-20141024135613-dd632973f1e7/go.mod h1:dt/ZhP58zS4L8KSrWDmTeBkI65Dw0HsyUHuEVlX15mw=
+gopkg.in/yaml.v2 v2.2.4/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
+gopkg.in/yaml.v2 v2.3.0/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
+gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=

metrics.go

@@ -0,0 +1,117 @@
+package main
+
+import (
+	"net/http"
+	"strconv"
+	"time"
+
+	"github.com/prometheus/client_golang/prometheus"
+)
+
+const namespace = "service"
+
+type MetricsResponseWriter struct {
+	rw     http.ResponseWriter
+	Code   string
+	Length int
+}
+
+func NewMetricsResponseWriter(r http.ResponseWriter) *MetricsResponseWriter {
+	return &MetricsResponseWriter{
+		rw: r,
+	}
+}
+
+func (m *MetricsResponseWriter) Header() http.Header {
+	return m.rw.Header()
+}
+func (m *MetricsResponseWriter) Write(in []byte) (int, error) {
+	m.Length += len(in)
+	return m.rw.Write(in)
+}
+func (m *MetricsResponseWriter) WriteHeader(statusCode int) {
+	m.rw.WriteHeader(statusCode)
+	m.Code = strconv.Itoa(statusCode)
+}
+
+var (
+	labels = []string{"status", "endpoint", "method"}
+
+	uptime = prometheus.NewCounterVec(
+		prometheus.CounterOpts{
+			Namespace: namespace,
+			Name:      "uptime",
+			Help:      "HTTP service uptime.",
+		}, nil,
+	)
+
+	reqCount = prometheus.NewCounterVec(
+		prometheus.CounterOpts{
+			Namespace: namespace,
+			Name:      "http_request_count_total",
+			Help:      "Total number of HTTP requests made.",
+		}, labels,
+	)
+
+	reqDuration = prometheus.NewHistogramVec(
+		prometheus.HistogramOpts{
+			Namespace: namespace,
+			Name:      "http_request_duration_seconds",
+			Help:      "HTTP request latencies in seconds.",
+		}, labels,
+	)
+
+	reqSizeBytes = prometheus.NewSummaryVec(
+		prometheus.SummaryOpts{
+			Namespace: namespace,
+			Name:      "http_request_size_bytes",
+			Help:      "HTTP request sizes in bytes.",
+		}, labels,
+	)
+
+	respSizeBytes = prometheus.NewSummaryVec(
+		prometheus.SummaryOpts{
+			Namespace: namespace,
+			Name:      "http_response_size_bytes",
+			Help:      "HTTP response sizes in bytes.",
+		}, labels,
+	)
+)
+
+// init registers the prometheus metrics
+func init() {
+	prometheus.MustRegister(uptime, reqCount, reqDuration, reqSizeBytes, respSizeBytes)
+	go recordUptime()
+}
+
+// recordUptime increases service uptime per second.
+func recordUptime() {
+	for range time.Tick(time.Second) {
+		uptime.WithLabelValues().Inc()
+	}
+}
+
+// calcRequestSize returns the size of request object.
+func calcRequestSize(r *http.Request) float64 {
+	size := 0
+	if r.URL != nil {
+		size = len(r.URL.String())
+	}
+
+	size += len(r.Method)
+	size += len(r.Proto)
+
+	for name, values := range r.Header {
+		size += len(name)
+		for _, value := range values {
+			size += len(value)
+		}
+	}
+	size += len(r.Host)
+
+	// r.Form and r.MultipartForm are assumed to be included in r.URL.
+	if r.ContentLength != -1 {
+		size += int(r.ContentLength)
+	}
+	return float64(size)
+}

middleware.go

@@ -18,6 +18,8 @@ import (
 func Middleware(fn func(http.ResponseWriter, *http.Request), o ServerOptions) http.Handler {
 	next := http.Handler(http.HandlerFunc(fn))
 
+	next = metrics(next)
+
 	if len(o.Endpoints) > 0 {
 		next = filterEndpoint(next, o)
 	}
@@ -129,6 +131,19 @@ func authorizeClient(next http.Handler, o ServerOptions) http.Handler {
 	})
 }
 
+func metrics(next http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		start := time.Now()
+		rw := NewMetricsResponseWriter(w)
+		next.ServeHTTP(rw, r)
+		lvs := []string{rw.Code, r.RequestURI, r.Method}
+		reqCount.WithLabelValues(lvs...).Inc()
+		reqDuration.WithLabelValues(lvs...).Observe(time.Since(start).Seconds())
+		reqSizeBytes.WithLabelValues(lvs...).Observe(calcRequestSize(r))
+		respSizeBytes.WithLabelValues(lvs...).Observe(float64(rw.Length))
+	})
+}
+
 func defaultHeaders(next http.Handler) http.Handler {
 	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		w.Header().Set("Server", fmt.Sprintf("imaginary %s (bimg %s)", Version, bimg.Version))

server.go

@@ -12,6 +12,8 @@ import (
 	"strings"
 	"syscall"
 	"time"
+
+	"github.com/prometheus/client_golang/prometheus/promhttp"
 )
 
 type ServerOptions struct {
@@ -115,6 +117,7 @@ func NewServerMux(o ServerOptions) http.Handler {
 	mux.Handle(join(o, "/"), Middleware(indexController(o), o))
 	mux.Handle(join(o, "/form"), Middleware(formController(o), o))
 	mux.Handle(join(o, "/health"), Middleware(healthController, o))
+	mux.Handle(join(o, "/metrics"), promhttp.Handler())
 
 	image := ImageMiddleware(o)
 	mux.Handle(join(o, "/resize"), image(Resize))