From f1f348edecec55189825eb8ee87bdbc3622dd59c Mon Sep 17 00:00:00 2001
From: Knut Ahlers <knut@ahlers.me>
Date: Thu, 7 Jul 2016 15:24:33 +0200
Subject: [PATCH] add metrics collection

---
 app.go            | 19 ++++++++++++++++++-
 metrics.go        | 38 ++++++++++++++++++++++++++++++++++++++
 service_github.go | 18 ++++++++++++++++++
 3 files changed, 74 insertions(+), 1 deletion(-)
 create mode 100644 metrics.go

diff --git a/app.go b/app.go
index 889d5a8..88d5f84 100644
--- a/app.go
+++ b/app.go
@@ -11,6 +11,7 @@ import (
 	"net/url"
 	"os"
 	"sort"
+	"strconv"
 	"strings"
 	"text/template"
 	"time"
@@ -20,8 +21,10 @@ import (
 	"golang.org/x/net/context"
 
 	"github.com/Luzifer/badge-gen/cache"
+	"github.com/Luzifer/go_helpers/accessLogger"
 	"github.com/Luzifer/rconfig"
 	"github.com/gorilla/mux"
+	"github.com/prometheus/client_golang/prometheus"
 	"github.com/tdewolff/minify"
 	"github.com/tdewolff/minify/svg"
 )
@@ -117,6 +120,7 @@ func main() {
 	r := mux.NewRouter()
 	r.HandleFunc("/v1/badge", generateBadge).Methods("GET")
 	r.HandleFunc("/{service}/{parameters:.*}", generateServiceBadge).Methods("GET")
+	r.Handle("/metrics", prometheus.Handler())
 	r.HandleFunc("/", handleDemoPage)
 
 	http.ListenAndServe(cfg.Listen, r)
@@ -127,6 +131,9 @@ func generateServiceBadge(res http.ResponseWriter, r *http.Request) {
 	service := vars["service"]
 	params := strings.Split(vars["parameters"], "/")
 
+	al := accessLogger.New(res)
+	start := time.Now()
+
 	ctx, cancel := context.WithTimeout(context.Background(), 1500*time.Millisecond)
 	defer cancel()
 
@@ -142,7 +149,17 @@ func generateServiceBadge(res http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	renderBadgeToResponse(res, r, title, text, color)
+	renderBadgeToResponse(al, r, title, text, color)
+
+	duration := float64(time.Since(start)) / float64(time.Microsecond)
+
+	requestCount.WithLabelValues(
+		service,
+		strings.ToLower(r.Method),
+		strconv.FormatInt(int64(al.StatusCode), 10),
+	).Inc()
+	responseSize.WithLabelValues(service).Observe(float64(al.Size))
+	requestDuration.WithLabelValues(service).Observe(duration)
 }
 
 func generateBadge(res http.ResponseWriter, r *http.Request) {
diff --git a/metrics.go b/metrics.go
new file mode 100644
index 0000000..d5fe097
--- /dev/null
+++ b/metrics.go
@@ -0,0 +1,38 @@
+package main
+
+import "github.com/prometheus/client_golang/prometheus"
+
+var (
+	requestCount    *prometheus.CounterVec
+	requestDuration *prometheus.SummaryVec
+	responseSize    *prometheus.SummaryVec
+)
+
+func init() {
+	initMetrics()
+}
+
+func initMetrics() {
+	so := prometheus.SummaryOpts{
+		Subsystem: "badge_gen",
+	}
+
+	reqCnt := prometheus.NewCounterVec(prometheus.CounterOpts{
+		Subsystem:   so.Subsystem,
+		Name:        "requests_total",
+		Help:        "Total number of HTTP requests made.",
+		ConstLabels: so.ConstLabels,
+	}, []string{"handler", "method", "code"})
+
+	so.Name = "response_size_bytes"
+	so.Help = "The HTTP response sizes in bytes."
+	resSz := prometheus.NewSummaryVec(so, []string{"handler"})
+
+	so.Name = "request_duration_microseconds"
+	so.Help = "The HTTP request latencies in microseconds."
+	reqDur := prometheus.NewSummaryVec(so, []string{"handler"})
+
+	requestCount = prometheus.MustRegisterOrGet(reqCnt).(*prometheus.CounterVec)
+	requestDuration = prometheus.MustRegisterOrGet(reqDur).(*prometheus.SummaryVec)
+	responseSize = prometheus.MustRegisterOrGet(resSz).(*prometheus.SummaryVec)
+}
diff --git a/service_github.go b/service_github.go
index 52fb2fb..d539d81 100644
--- a/service_github.go
+++ b/service_github.go
@@ -5,15 +5,26 @@ import (
 	"errors"
 	"net/http"
 	"regexp"
+	"strconv"
 	"strings"
 	"time"
 
+	"github.com/prometheus/client_golang/prometheus"
+
 	"golang.org/x/net/context"
 	"golang.org/x/net/context/ctxhttp"
 )
 
+var (
+	githubRemainingLimit prometheus.Gauge
+)
+
 func init() {
 	registerServiceHandler("github", githubServiceHandler{})
+	githubRemainingLimit = prometheus.MustRegisterOrGet(prometheus.NewGauge(prometheus.GaugeOpts{
+		Name: "github_remaining_limit",
+		Help: "Remaining requests in GitHub rate limit until next reset",
+	})).(prometheus.Gauge)
 }
 
 type githubRelease struct {
@@ -275,5 +286,12 @@ func (g githubServiceHandler) fetchAPI(ctx context.Context, path string, headers
 	}
 	defer resp.Body.Close()
 
+	if rlr := resp.Header.Get("X-RateLimit-Remaining"); rlr != "" {
+		v, err := strconv.ParseInt(rlr, 10, 64)
+		if err == nil {
+			githubRemainingLimit.Set(float64(v))
+		}
+	}
+
 	return json.NewDecoder(resp.Body).Decode(out)
 }