api/prometheus: add prometheus metrics to API routes

api/context/context.go

@@ -15,28 +15,45 @@
 package context
 
 import (
-	"fmt"
 	"net/http"
+	"strconv"
+	"time"
 
 	"github.com/coreos/pkg/capnslog"
 	"github.com/julienschmidt/httprouter"
+	"github.com/prometheus/client_golang/prometheus"
 
 	"github.com/coreos/clair/database"
+	"github.com/coreos/clair/utils"
 )
 
-var log = capnslog.NewPackageLogger("github.com/coreos/clair", "api")
+var (
+	log = capnslog.NewPackageLogger("github.com/coreos/clair", "api")
 
-type Handler func(http.ResponseWriter, *http.Request, httprouter.Params, *RouteContext) int
+	promResponseDurationMilliseconds = prometheus.NewHistogramVec(prometheus.HistogramOpts{
+		Name:    "clair_api_response_duration_milliseconds",
+		Help:    "The duration of time it takes to receieve and write a response to an API request",
+		Buckets: prometheus.ExponentialBuckets(9.375, 2, 10),
+	}, []string{"route", "code"})
+)
+
+func init() {
+	prometheus.MustRegister(promResponseDurationMilliseconds)
+}
+
+type Handler func(http.ResponseWriter, *http.Request, httprouter.Params, *RouteContext) (route string, status int)
 
 func HTTPHandler(handler Handler, ctx *RouteContext) httprouter.Handle {
 	return func(w http.ResponseWriter, r *http.Request, p httprouter.Params) {
-		status := handler(w, r, p, ctx)
-		statusStr := fmt.Sprintf("%d", status)
+		start := time.Now()
+		route, status := handler(w, r, p, ctx)
+		statusStr := strconv.Itoa(status)
 		if status == 0 {
 			statusStr = "???"
 		}
+		utils.PrometheusObserveTimeMilliseconds(promResponseDurationMilliseconds.WithLabelValues(route, statusStr), start)
 
-		log.Infof("%s %s %s %s", statusStr, r.Method, r.RequestURI, r.RemoteAddr)
+		log.Infof("%s \"%s %s\" %s", r.RemoteAddr, r.Method, r.RequestURI, statusStr)
 	}
 }
 

api/router.go

@@ -62,6 +62,9 @@ func newHealthHandler(ctx *context.RouteContext) http.Handler {
 	return router
 }
 
-func getHealth(w http.ResponseWriter, r *http.Request, p httprouter.Params, ctx *context.RouteContext) int {
-	return 0
+func getHealth(w http.ResponseWriter, r *http.Request, p httprouter.Params, ctx *context.RouteContext) (string, int) {
+	if ctx.Store.Ping() {
+		return "health", http.StatusOK
+	}
+	return "health", http.StatusInternalServerError
 }