http: Add runtime metrics

3 files changed, 37 insertions, 33 deletions

diff --git a/http/http.go b/http/http.go
index e783319..5ff5fd3 100644
--- a/http/http.go
+++ b/http/http.go
@@ -1,11 +1,9 @@
 package http
 
 import (
-	"bytes"
 	"context"
 	"encoding/json"
 	"fmt"
-	"io"
 	"log"
 	"net"
 	"net/http"
@@ -22,7 +20,7 @@ const (
 	jsonMediaType = "application/json"
 )
 
-// A Server defines paramaters for running an HTTP server. The HTTP server serves an API for inspecting cache contents
+// A Server defines parameters for running an HTTP server. The HTTP server serves an API for inspecting cache contents
 // and request log.
 type Server struct {
 	cache    *cache.Cache
@@ -99,10 +97,10 @@ func newHTTPBadRequest(err error) *httpError {
 func NewServer(cache *cache.Cache, logger *sql.Logger, sqlCache *sql.Cache, addr string) *Server {
 	server := &http.Server{Addr: addr}
 	s := &Server{
+		server:   server,
 		cache:    cache,
 		logger:   logger,
 		sqlCache: sqlCache,
-		server:   server,
 	}
 	s.server.Handler = s.handler()
 	return s
@@ -111,9 +109,11 @@ func NewServer(cache *cache.Cache, logger *sql.Logger, sqlCache *sql.Cache, addr
 func (s *Server) handler() http.Handler {
 	r := &router{}
 	r.route(http.MethodGet, "/cache/v1/", s.cacheHandler)
-	r.route(http.MethodGet, "/log/v1/", s.logHandler)
-	r.route(http.MethodGet, "/metric/v1/", s.metricHandler)
 	r.route(http.MethodDelete, "/cache/v1/", s.cacheResetHandler)
+	if s.logger != nil {
+		r.route(http.MethodGet, "/log/v1/", s.logHandler)
+		r.route(http.MethodGet, "/metric/v1/", s.metricHandler)
+	}
 	return r.handler()
 }
 
@@ -148,21 +148,6 @@ func writeJSON(w http.ResponseWriter, data interface{}) {
 	w.Write(b)
 }
 
-func writeMetric(w io.StringWriter, name, help string, value int64) {
-	w.WriteString("# HELP ")
-	w.WriteString(name)
-	w.WriteString(" ")
-	w.WriteString(help)
-	w.WriteString("\n")
-	w.WriteString("# TYPE ")
-	w.WriteString(name)
-	w.WriteString(" gauge\n")
-	w.WriteString(name)
-	w.WriteString(" ")
-	w.WriteString(strconv.FormatInt(value, 10))
-	w.WriteString("\n")
-}
-
 func (s *Server) cacheHandler(w http.ResponseWriter, r *http.Request) *httpError {
 	count, err := countFrom(r)
 	if err != nil {
@@ -268,11 +253,9 @@ func (s *Server) prometheusMetricHandler(w http.ResponseWriter, r *http.Request)
 	if err != nil {
 		return newHTTPError(err)
 	}
-	var buf bytes.Buffer
-	writeMetric(&buf, "zdns_requests_total", "The total number of DNS requests.", lstats.Total)
-	writeMetric(&buf, "zdns_requests_hijacked", "The number of hijacked DNS requests.", lstats.Hijacked)
-	w.Header().Set("Content-Type", "text/plain; version=0.0.4")
-	w.Write(buf.Bytes())
+	totalRequestsGauge.Set(float64(lstats.Total))
+	hijackedRequestsGauge.Set(float64(lstats.Hijacked))
+	prometheusHandler.ServeHTTP(w, r)
 	return nil
 }
 
diff --git a/http/http_test.go b/http/http_test.go
index 905e338..ac95697 100644
--- a/http/http_test.go
+++ b/http/http_test.go
@@ -37,8 +37,8 @@ func testServer() (*httptest.Server, *Server) {
 	logger := sql.NewLogger(sqlClient, sql.LogAll, 0)
 	sqlCache := sql.NewCache(sqlClient)
 	cache := cache.New(10, nil)
-	server := Server{logger: logger, cache: cache, sqlCache: sqlCache}
-	return httptest.NewServer(server.handler()), &server
+	server := NewServer(cache, logger, sqlCache, "")
+	return httptest.NewServer(server.handler()), server
 }
 
 func httpGet(url string) (*http.Response, string, error) {
@@ -91,14 +91,15 @@ func TestRequests(t *testing.T) {
 		`{"time":"RFC3339","remote_addr":"127.0.0.42","hijacked":false,"type":"A","question":"example.com.","answers":["192.0.2.101","192.0.2.100"]}]`
 	lr2 := `[{"time":"RFC3339","remote_addr":"127.0.0.254","hijacked":true,"type":"AAAA","question":"example.com.","answers":["2001:db8::1"]}]`
 	mr1 := `{"summary":{"log":{"since":"RFC3339","total":2,"hijacked":1,"pending_tasks":0},"cache":{"size":2,"capacity":10,"pending_tasks":0,"backend":{"pending_tasks":0}}},"requests":[{"time":"RFC3339","count":2}]}`
-	mr2 := `# HELP zdns_requests_total The total number of DNS requests.
-# TYPE zdns_requests_total gauge
-zdns_requests_total 2
+	mr2 := `
+<ANY>
 # HELP zdns_requests_hijacked The number of hijacked DNS requests.
 # TYPE zdns_requests_hijacked gauge
 zdns_requests_hijacked 1
+# HELP zdns_requests_total The total number of DNS requests.
+# TYPE zdns_requests_total gauge
+zdns_requests_total 2
 `
-
 	var tests = []struct {
 		method      string
 		url         string
@@ -115,7 +116,7 @@ zdns_requests_hijacked 1
 		{http.MethodGet, "/cache/v1/?n=1", cr2, 200, jsonMediaType},
 		{http.MethodGet, "/metric/v1/", mr1, 200, jsonMediaType},
 		{http.MethodGet, "/metric/v1/?format=basic", mr1, 200, jsonMediaType},
-		{http.MethodGet, "/metric/v1/?format=prometheus", mr2, 200, "text/plain; version=0.0.4"},
+		{http.MethodGet, "/metric/v1/?format=prometheus", mr2, 200, "text/plain; version=0.0.4; charset=utf-8"},
 		{http.MethodGet, "/metric/v1/?resolution=1m", mr1, 200, jsonMediaType},
 		{http.MethodGet, "/metric/v1/?resolution=0", mr1, 200, jsonMediaType},
 		{http.MethodGet, "/metric/v1/?format=foo", `{"status":400,"message":"invalid metric format: foo"}`, 400, jsonMediaType},
@@ -151,6 +152,7 @@ zdns_requests_hijacked 1
 		got := string(data)
 		want := regexp.QuoteMeta(tt.response)
 		want = strings.ReplaceAll(want, "RFC3339", `\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}Z`)
+		want = strings.ReplaceAll(want, "<ANY>", ".*")
 		matched, err := regexp.MatchString(want, got)
 		if err != nil {
 			t.Fatal(err)
diff --git a/http/prometheus.go b/http/prometheus.go
new file mode 100644
index 0000000..7b78055
--- /dev/null
+++ b/http/prometheus.go
@@ -0,0 +1,19 @@
+package http
+
+import (
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promauto"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
+)
+
+var (
+	totalRequestsGauge = promauto.NewGauge(prometheus.GaugeOpts{
+		Name: "zdns_requests_total",
+		Help: "The total number of DNS requests.",
+	})
+	hijackedRequestsGauge = promauto.NewGauge(prometheus.GaugeOpts{
+		Name: "zdns_requests_hijacked",
+		Help: "The number of hijacked DNS requests.",
+	})
+	prometheusHandler = promhttp.Handler()
+)