Add metrics exporter

Dockerfile

@@ -14,6 +14,7 @@ RUN CGO_ENABLED=0 GOOS=linux GOARCH=amd64 go build -ldflags="-w -s" -o /build/${
 FROM alpine:3.8
 ENV BINARY oidc-starter
 EXPOSE 5555
+
 RUN apk --no-cache add ca-certificates
 
 WORKDIR /app

go.mod

@@ -5,6 +5,7 @@ require (
 	github.com/golang/protobuf v1.2.0
 	github.com/inconshreveable/mousetrap v1.0.0
 	github.com/pquerna/cachecontrol v0.0.0-20180517163645-1555304b9b35
+	github.com/prometheus/client_golang v0.9.2
 	github.com/spf13/cobra v0.0.3
 	github.com/spf13/pflag v1.0.3
 	golang.org/x/crypto v0.0.0-20181203042331-505ab145d0a9

go.sum

@@ -1,10 +1,23 @@
+github.com/beorn7/perks v0.0.0-20180321164747-3a771d992973 h1:xJ4a3vCFaGF/jqvzLMYoU8P317H5OQ+Via4RmuPwCS0=
+github.com/beorn7/perks v0.0.0-20180321164747-3a771d992973/go.mod h1:Dwedo/Wpr24TaqPxmxbtue+5NUziq4I4S80YR8gNf3Q=
 github.com/coreos/go-oidc v2.0.0+incompatible h1:+RStIopZ8wooMx+Vs5Bt8zMXxV1ABl5LbakNExNmZIg=
 github.com/coreos/go-oidc v2.0.0+incompatible/go.mod h1:CgnwVTmzoESiwO9qyAFEMiHoZ1nMCKZlZ9V6mm3/LKc=
 github.com/golang/protobuf v1.1.0/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
+github.com/golang/protobuf v1.2.0 h1:P3YflyNX/ehuJFLhxviNdFxQPkGK5cDcApsge1SqnvM=
 github.com/golang/protobuf v1.2.0/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
 github.com/inconshreveable/mousetrap v1.0.0/go.mod h1:PxqpIevigyE2G7u3NXJIT2ANytuPF1OarO4DADm73n8=
+github.com/matttproud/golang_protobuf_extensions v1.0.1 h1:4hp9jkHxhMHkqkrB3Ix0jegS5sx/RkqARlsWZ6pIwiU=
+github.com/matttproud/golang_protobuf_extensions v1.0.1/go.mod h1:D8He9yQNgCq6Z5Ld7szi9bcBfOoFv/3dc6xSMkL2PC0=
 github.com/pquerna/cachecontrol v0.0.0-20180517163645-1555304b9b35 h1:J9b7z+QKAmPf4YLrFg6oQUotqHQeUNWwkvo7jZp1GLU=
 github.com/pquerna/cachecontrol v0.0.0-20180517163645-1555304b9b35/go.mod h1:prYjPmNq4d1NPVmpShWobRqXY3q7Vp+80DqgxxUrUIA=
+github.com/prometheus/client_golang v0.9.2 h1:awm861/B8OKDd2I/6o1dy3ra4BamzKhYOiGItCeZ740=
+github.com/prometheus/client_golang v0.9.2/go.mod h1:OsXs2jCmiKlQ1lTBmv21f2mNfw4xf/QclQDMrYNZzcM=
+github.com/prometheus/client_model v0.0.0-20180712105110-5c3871d89910 h1:idejC8f05m9MGOsuEi1ATq9shN03HrxNkD/luQvxCv8=
+github.com/prometheus/client_model v0.0.0-20180712105110-5c3871d89910/go.mod h1:MbSGuTsp3dbXC40dX6PRTWyKYBIrTGTE9sqQNg2J8bo=
+github.com/prometheus/common v0.0.0-20181126121408-4724e9255275 h1:PnBWHBf+6L0jOqq0gIVUe6Yk0/QMZ640k6NvkxcBf+8=
+github.com/prometheus/common v0.0.0-20181126121408-4724e9255275/go.mod h1:daVV7qP5qjZbuso7PdcryaAu0sAZbrN9i7WWcTMWvro=
+github.com/prometheus/procfs v0.0.0-20181204211112-1dc9a6cbc91a h1:9a8MnZMP0X2nLJdBg+pBmGgkJlSaKC2KaQmTCk1XDtE=
+github.com/prometheus/procfs v0.0.0-20181204211112-1dc9a6cbc91a/go.mod h1:c3At6R/oaqEKCNdg8wHV1ftS6bRYblBhIjjI8uT2IGk=
 github.com/spf13/cobra v0.0.3 h1:ZlrZ4XsMRm04Fr5pSFxBgfND2EBVa1nLpiy1stUsX/8=
 github.com/spf13/cobra v0.0.3/go.mod h1:1l0Ry5zgKvJasoi3XT1TypsSe7PqH0Sj9dhYf7v3XqQ=
 github.com/spf13/pflag v1.0.1/go.mod h1:DYY7MBk1bdzusC3SYhjObp+wFpr4gzcvqqNjLnInEg4=
@@ -17,12 +30,14 @@ golang.org/x/crypto v0.0.0-20181203042331-505ab145d0a9/go.mod h1:6SG95UA2DQfeDnf
 golang.org/x/net v0.0.0-20180530234432-1e491301e022 h1:MVYFTUmVD3/+ERcvRRI+P/C2+WOUimXh+Pd8LVsklZ4=
 golang.org/x/net v0.0.0-20180530234432-1e491301e022/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=
 golang.org/x/net v0.0.0-20180724234803-3673e40ba225/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=
+golang.org/x/net v0.0.0-20181201002055-351d144fa1fc/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=
 golang.org/x/net v0.0.0-20181220203305-927f97764cc3 h1:eH6Eip3UpmR+yM/qI9Ijluzb1bNv/cAU/n+6l8tRSis=
 golang.org/x/net v0.0.0-20181220203305-927f97764cc3/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=
 golang.org/x/oauth2 v0.0.0-20180603041954-1e0a3fa8ba9a h1:1Fy38jwe/QZhQfFQBy6dMj9F/WU1C+jo3/zLNr/WhW4=
 golang.org/x/oauth2 v0.0.0-20180603041954-1e0a3fa8ba9a/go.mod h1:N/0e6XlmueqKjAGxoOufVs8QHGRruUQn6yWY3a++T0U=
 golang.org/x/oauth2 v0.0.0-20181203162652-d668ce993890 h1:uESlIz09WIHT2I+pasSXcpLYqYK8wHcdCetU3VuMBJE=
 golang.org/x/oauth2 v0.0.0-20181203162652-d668ce993890/go.mod h1:N/0e6XlmueqKjAGxoOufVs8QHGRruUQn6yWY3a++T0U=
+golang.org/x/sync v0.0.0-20181108010431-42b317875d0f/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
 google.golang.org/appengine v1.0.0/go.mod h1:EbEs0AVv82hx2wNQdGPgUI5lhzA/G0D9YwlJXL52JkM=
 google.golang.org/appengine v1.4.0/go.mod h1:xpcJRLb0r/rnEns0DIKYYv+WjYCduHsrkT7/EB5XEv4=

main.go

@@ -20,12 +20,13 @@ import (
 	"time"
 
 	"github.com/coreos/go-oidc"
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promauto"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
 	"github.com/spf13/cobra"
 	"golang.org/x/oauth2"
 )
 
-const exampleAppState = "I wish to wash my irish wristwatch"
-
 type app struct {
 	clientID      string
 	clientSecret  string
@@ -192,15 +193,43 @@ func cmd() *cobra.Command {
 			a.provider = provider
 			a.verifier = provider.Verifier(&oidc.Config{ClientID: a.clientID})
 
-			http.HandleFunc(listenURL.Path, a.handleIndex)
-			http.HandleFunc(redirectURL.Path, a.handleCallback)
-			http.HandleFunc(path.Join(listenURL.Path, "healthz"), a.handleHealthz)
+			indexHandler := promhttp.InstrumentHandlerCounter(
+				promauto.NewCounterVec(
+					prometheus.CounterOpts{
+						Name: "oidc_starter_index_requests_total",
+						Help: "Total number of index requests by HTTP status code.",
+					},
+					[]string{"code"},
+				),
+				http.HandlerFunc(a.handleIndex),
+			)
+			http.HandleFunc(listenURL.Path, indexHandler)
+			log.Printf("Registered index handler at: %s", listenURL.Path)
+
+			callbackHandler := promhttp.InstrumentHandlerCounter(
+				promauto.NewCounterVec(
+					prometheus.CounterOpts{
+						Name: "oidc_starter_callback_response_total",
+						Help: "Total number of index response by HTTP status code.",
+					},
+					[]string{"code"},
+				),
+				http.HandlerFunc(a.handleCallback),
+			)
+			http.HandleFunc(redirectURL.Path, callbackHandler)
+			log.Printf("Registered callback handler at: %s", redirectURL.Path)
+
+			healthzPattern := path.Join(listenURL.Path, "healthz")
+			http.HandleFunc(healthzPattern, a.handleHealthz)
+			log.Printf("Registered healthz handler at: %s", healthzPattern)
 
 			fs := http.FileServer(http.Dir("web/static/"))
-			staticURI := path.Join(listenURL.Path, "static") + "/"
+			staticPattern := path.Join(listenURL.Path, "static") + "/"
+			http.Handle(staticPattern, http.StripPrefix(staticPattern, fs))
+			log.Printf("Registered static assets handler at: %s", staticPattern)
 
-			log.Printf("Registered static assets handler at: %s", staticURI)
-			http.Handle(staticURI, http.StripPrefix(staticURI, fs))
+			http.Handle("/metrics", promhttp.Handler())
+			log.Printf("Registered metrics handler at: %s", "/metrics")
 
 			switch listenURL.Scheme {
 			case "http":