2 files changed, 111 insertions, 0 deletions
diff --git a/middleware/prometheus/handler.go b/middleware/prometheus/handler.go
new file mode 100644
index 000000000..eb82b8aff
--- /dev/null
+++ b/middleware/prometheus/handler.go
@@ -0,0 +1,31 @@
+package metrics
+
+import (
+	"strconv"
+	"time"
+
+	"github.com/miekg/coredns/middleware"
+	"github.com/miekg/dns"
+)
+
+func (m *Metrics) ServeDNS(w dns.ResponseWriter, r *dns.Msg) (int, error) {
+	context := middleware.Context{W: w, Req: r}
+
+	qname := context.Name()
+	qtype := context.Type()
+	zone := middleware.Zones(m.ZoneNames).Matches(qname)
+	if zone == "" {
+		zone = "."
+	}
+
+	// Record response to get status code and size of the reply.
+	rw := middleware.NewResponseRecorder(w)
+	status, err := m.Next.ServeDNS(rw, r)
+
+	requestCount.WithLabelValues(zone, qtype).Inc()
+	requestDuration.WithLabelValues(zone).Observe(float64(time.Since(rw.Start()) / time.Second))
+	responseSize.WithLabelValues(zone).Observe(float64(rw.Size()))
+	responseRcode.WithLabelValues(zone, strconv.Itoa(rw.Rcode())).Inc()
+
+	return status, err
+}
diff --git a/middleware/prometheus/metrics.go b/middleware/prometheus/metrics.go
new file mode 100644
index 000000000..4c989f640
--- /dev/null
+++ b/middleware/prometheus/metrics.go
@@ -0,0 +1,80 @@
+package metrics
+
+import (
+	"fmt"
+	"net/http"
+	"sync"
+
+	"github.com/miekg/coredns/middleware"
+	"github.com/prometheus/client_golang/prometheus"
+)
+
+const namespace = "daddy"
+
+var (
+	requestCount    *prometheus.CounterVec
+	requestDuration *prometheus.HistogramVec
+	responseSize    *prometheus.HistogramVec
+	responseRcode   *prometheus.CounterVec
+)
+
+const path = "/metrics"
+
+// Metrics holds the prometheus configuration. The metrics' path is fixed to be /metrics
+type Metrics struct {
+	Next      middleware.Handler
+	Addr      string // where to we listen
+	Once      sync.Once
+	ZoneNames []string
+}
+
+func (m *Metrics) Start() error {
+	m.Once.Do(func() {
+		define("")
+
+		prometheus.MustRegister(requestCount)
+		prometheus.MustRegister(requestDuration)
+		prometheus.MustRegister(responseSize)
+		prometheus.MustRegister(responseRcode)
+
+		http.Handle(path, prometheus.Handler())
+		go func() {
+			fmt.Errorf("%s", http.ListenAndServe(m.Addr, nil))
+		}()
+	})
+	return nil
+}
+
+func define(subsystem string) {
+	if subsystem == "" {
+		subsystem = "dns"
+	}
+	requestCount = prometheus.NewCounterVec(prometheus.CounterOpts{
+		Namespace: namespace,
+		Subsystem: subsystem,
+		Name:      "request_count_total",
+		Help:      "Counter of DNS requests made per zone and type.",
+	}, []string{"zone", "qtype"})
+
+	requestDuration = prometheus.NewHistogramVec(prometheus.HistogramOpts{
+		Namespace: namespace,
+		Subsystem: subsystem,
+		Name:      "request_duration_seconds",
+		Help:      "Histogram of the time (in seconds) each request took.",
+	}, []string{"zone"})
+
+	responseSize = prometheus.NewHistogramVec(prometheus.HistogramOpts{
+		Namespace: namespace,
+		Subsystem: subsystem,
+		Name:      "response_size_bytes",
+		Help:      "Size of the returns response in bytes.",
+		Buckets:   []float64{0, 100, 200, 300, 400, 511, 1023, 2047, 4095, 8291, 16e3, 32e3, 48e3, 64e3},
+	}, []string{"zone"})
+
+	responseRcode = prometheus.NewCounterVec(prometheus.CounterOpts{
+		Namespace: namespace,
+		Subsystem: subsystem,
+		Name:      "rcode_code_count_total",
+		Help:      "Counter of response status codes.",
+	}, []string{"zone", "rcode"})
+}