Update Prometheus metrics tracking (#459)

Signed-off-by: Andrew Morgan <andrewm@matrix.org>

src/github.com/matrix-org/dendrite/clientapi/routing/register.go

@@ -40,9 +40,20 @@ import (
 	"github.com/matrix-org/dendrite/clientapi/jsonerror"
 	"github.com/matrix-org/gomatrixserverlib"
 	"github.com/matrix-org/util"
+	"github.com/prometheus/client_golang/prometheus"
 	log "github.com/sirupsen/logrus"
 )
 
+var (
+	// Prometheus metrics
+	amtRegUsers = prometheus.NewCounter(
+		prometheus.CounterOpts{
+			Name: "dendrite_clientapi_reg_users_total",
+			Help: "Total number of registered users",
+		},
+	)
+)
+
 const (
 	minPasswordLength = 8   // http://matrix.org/docs/spec/client_server/r0.2.0.html#password-based
 	maxPasswordLength = 512 // https://github.com/matrix-org/synapse/blob/v0.20.0/synapse/rest/client/v2_alpha/register.py#L161
@@ -50,6 +61,11 @@ const (
 	sessionIDLength   = 24
 )
 
+func init() {
+	// Register prometheus metrics. They must be registered to be exposed.
+	prometheus.MustRegister(amtRegUsers)
+}
+
 // sessionsDict keeps track of completed auth stages for each session.
 type sessionsDict struct {
 	sessions map[string][]authtypes.LoginType
@@ -665,6 +681,9 @@ func completeRegistration(
 		}
 	}
 
+	// Increment prometheus counter for created users
+	amtRegUsers.Inc()
+
 	return util.JSONResponse{
 		Code: http.StatusOK,
 		JSON: registerResponse{

src/github.com/matrix-org/dendrite/cmd/dendrite-monolith-server/main.go

@@ -30,6 +30,8 @@ import (
 	"github.com/matrix-org/dendrite/publicroomsapi"
 	"github.com/matrix-org/dendrite/roomserver"
 	"github.com/matrix-org/dendrite/syncapi"
+
+	"github.com/prometheus/client_golang/prometheus/promhttp"
 	"github.com/sirupsen/logrus"
 )
 
@@ -66,16 +68,21 @@ func main() {
 
 	httpHandler := common.WrapHandlerInCORS(base.APIMux)
 
+	// Set up the API endpoints we handle. /metrics is for prometheus, and is
+	// not wrapped by CORS, while everything else is
+	http.Handle("/metrics", promhttp.Handler())
+	http.Handle("/", httpHandler)
+
 	// Expose the matrix APIs directly rather than putting them under a /api path.
 	go func() {
 		logrus.Info("Listening on ", *httpBindAddr)
-		logrus.Fatal(http.ListenAndServe(*httpBindAddr, httpHandler))
+		logrus.Fatal(http.ListenAndServe(*httpBindAddr, nil))
 	}()
 	// Handle HTTPS if certificate and key are provided
 	go func() {
 		if *certFile != "" && *keyFile != "" {
 			logrus.Info("Listening on ", *httpsBindAddr)
-			logrus.Fatal(http.ListenAndServeTLS(*httpsBindAddr, *certFile, *keyFile, httpHandler))
+			logrus.Fatal(http.ListenAndServeTLS(*httpsBindAddr, *certFile, *keyFile, nil))
 		}
 	}()
 

src/github.com/matrix-org/dendrite/common/basecomponent/base.go

@@ -134,7 +134,6 @@ func (b *BaseDendrite) CreateFederationClient() *gomatrixserverlib.FederationCli
 // ApiMux under /api/ and adds a prometheus handler under /metrics.
 func (b *BaseDendrite) SetupAndServeHTTP(addr string) {
 	common.SetupHTTPAPI(http.DefaultServeMux, common.WrapHandlerInCORS(b.APIMux))
-
 	logrus.Infof("Starting %s server on %s", b.componentName, addr)
 
 	err := http.ListenAndServe(addr, nil)

src/github.com/matrix-org/dendrite/common/httpapi.go

@@ -10,7 +10,7 @@ import (
 	"github.com/matrix-org/util"
 	opentracing "github.com/opentracing/opentracing-go"
 	"github.com/opentracing/opentracing-go/ext"
-	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
 )
 
 // MakeAuthAPI turns a util.JSONRequestHandler function into an http.Handler which checks the access token in the request.
@@ -36,7 +36,7 @@ func MakeExternalAPI(metricsName string, f func(*http.Request) util.JSONResponse
 		h.ServeHTTP(w, req)
 	}
 
-	return prometheus.InstrumentHandler(metricsName, http.HandlerFunc(withSpan))
+	return http.HandlerFunc(withSpan)
 }
 
 // MakeInternalAPI turns a util.JSONRequestHandler function into an http.Handler.
@@ -62,7 +62,7 @@ func MakeInternalAPI(metricsName string, f func(*http.Request) util.JSONResponse
 		h.ServeHTTP(w, req)
 	}
 
-	return prometheus.InstrumentHandler(metricsName, http.HandlerFunc(withSpan))
+	return http.HandlerFunc(withSpan)
 }
 
 // MakeFedAPI makes an http.Handler that checks matrix federation authentication.
@@ -87,8 +87,7 @@ func MakeFedAPI(
 // SetupHTTPAPI registers an HTTP API mux under /api and sets up a metrics
 // listener.
 func SetupHTTPAPI(servMux *http.ServeMux, apiMux http.Handler) {
-	// This is deprecated.
-	servMux.Handle("/metrics", prometheus.Handler()) // nolint: megacheck, staticcheck
+	servMux.Handle("/metrics", promhttp.Handler())
 	servMux.Handle("/api/", http.StripPrefix("/api", apiMux))
 }