Merge pull request #18 from keratin/metrics

add: `GET /metrics` (authenticated)

api/meta/routing.go

@@ -3,6 +3,7 @@ package meta
 import (
 	"github.com/keratin/authn-server/api"
 	"github.com/keratin/authn-server/lib/route"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
 )
 
 func Routes(app *api.App) []*route.HandledRoute {
@@ -24,5 +25,8 @@ func Routes(app *api.App) []*route.HandledRoute {
 		route.Get("/stats").
 			SecuredWith(authentication).
 			Handle(getStats(app)),
+		route.Get("/metrics").
+			SecuredWith(authentication).
+			Handle(promhttp.Handler()),
 	}
 }

api/views/root.ego

@@ -14,7 +14,8 @@ func Root(w io.Writer) {
       <div style="flex: 1 0 auto;">
         <ul>
           <li><a href="health">Health</a></li>
-          <li><a href="stats">Stats</a></li>
+          <li><a href="stats">Active Users</a></li>
+          <li><a href="metrics">Server Metrics</a></li>
           <li><a href="jwks">Keys</a></li>
           <li><a href="https://github.com/keratin/authn-server">GitHub</a></li>
           <li><a href="https://github.com/keratin/authn-server/blob/master/docs/README.md">Docs</a></li>

docs/api.md

@@ -481,7 +481,7 @@ This endpoint is primarily used by backend client libraries to fetch the public
 
 ### Service Stats
 
-Visibility: Public
+Visibility: Private
 
 `GET /stats`
 
@@ -506,3 +506,23 @@ Time periods are labeled in ISO8601 formats:
         "monthly": {}
       }
     }
+
+### Server Stats
+
+Visibility: Private
+
+`GET /metrics`
+
+Returns server stats (memory usage) and traffic stats (counts, timings) that may be used to monitor and alert on server health. The data is formatted for consumption by Prometheus-compatible collectors.
+
+#### Success:
+
+    200 Ok
+
+    # HELP go_goroutines Number of goroutines that currently exist.
+    # TYPE go_goroutines gauge
+    go_goroutines 10
+    [...]
+    # HELP http_requests_total How many HTTP requests processed, partitioned by name and status code
+    # TYPE http_requests_total counter
+    http_requests_total{code="200",name="GET /health"} 97

glide.yaml

@@ -29,3 +29,8 @@ import:
 - package: github.com/getsentry/raven-go
 - package: github.com/sirupsen/logrus
   version: ^1.0.3
+- package: github.com/prometheus/client_golang
+  version: ^0.9.0-pre1
+  subpackages:
+  - prometheus
+- package: github.com/felixge/httpsnoop

lib/route/instrument.go

@@ -0,0 +1,41 @@
+package route
+
+import (
+	"net/http"
+	"strconv"
+
+	"github.com/felixge/httpsnoop"
+
+	"github.com/prometheus/client_golang/prometheus"
+)
+
+var (
+	httpRequests = prometheus.NewCounterVec(
+		prometheus.CounterOpts{
+			Name: "http_requests_total",
+			Help: "How many HTTP requests processed, partitioned by name and status code",
+		},
+		[]string{"name", "code"},
+	)
+	httpTimings = prometheus.NewHistogramVec(
+		prometheus.HistogramOpts{
+			Name:    "http_request_times",
+			Help:    "The duration of HTTP requests, partitioned by name",
+			Buckets: prometheus.ExponentialBuckets(0.001, 10, 5),
+		},
+		[]string{"name"},
+	)
+)
+
+func init() {
+	prometheus.MustRegister(httpRequests)
+	prometheus.MustRegister(httpTimings)
+}
+
+func instrumentRoute(name string, next http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		metrics := httpsnoop.CaptureMetrics(next, w, r)
+		httpRequests.WithLabelValues(name, strconv.Itoa(metrics.Code)).Inc()
+		httpTimings.WithLabelValues(name).Observe(float64(metrics.Duration.Seconds()))
+	})
+}

lib/route/route.go

@@ -71,6 +71,6 @@ func Attach(router *mux.Router, pathPrefix string, routes ...*HandledRoute) {
 			PathPrefix(pathPrefix).
 			Methods(r.verb).
 			Path(r.tpl).
-			Handler(r.security(r.handler))
+			Handler(instrumentRoute(r.verb+" "+r.tpl, r.security(r.handler)))
 	}
 }