add dogstatsd utility

.gitignore

@@ -26,3 +26,6 @@ _testmain.go
 
 # Emacs
 *~
+
+# Commands
+/dogstatsd

Dockerfile

@@ -0,0 +1,12 @@
+FROM golang:alpine
+
+COPY . /go/src/github.com/segmentio/stats
+
+ENV CGO_ENABLED=0
+RUN apk add --no-cache git && \
+    cd /go/src/github.com/segmentio/stats && \
+    go build -v -o /dogstatsd ./cmd/dogstatsd && \
+    apk del git && \
+    rm -rf /go/*
+
+ENTRYPOINT ["/dogstatsd"]

cmd/dogstatsd/main.go

@@ -0,0 +1,21 @@
+package main
+
+import (
+	"flag"
+	"log"
+	"net"
+
+	"github.com/segmentio/stats/datadog"
+)
+
+func main() {
+	var bind string
+
+	flag.StringVar(&bind, "bind", ":8125", "The network address to listen on for incoming UDP datagrams")
+	flag.Parse()
+	log.Printf("listening for incoming UDP datagram on %s", bind)
+
+	datadog.ListenAndServe(bind, datadog.HandlerFunc(func(metric datadog.Metric, from net.Addr) {
+		log.Print(metric)
+	}))
+}

datadog/metric.go

@@ -1,6 +1,11 @@
 package datadog
 
-import "github.com/segmentio/stats"
+import (
+	"fmt"
+	"sync"
+
+	"github.com/segmentio/stats"
+)
 
 // MetricType is an enumeration providing symbols to represent the different
 // metric types upported by datadog.
@@ -21,3 +26,24 @@ type Metric struct {
 	Tags      []stats.Tag     // the list of tags set on the metric
 	Namespace stats.Namespace // the metric namespace (never populated by parsing operations)
 }
+
+// String satisfies the fmt.Stringer interface.
+func (m Metric) String() string {
+	return fmt.Sprint(m)
+}
+
+// Format satisfies the fmt.Formatter interface.
+func (m Metric) Format(f fmt.State, _ rune) {
+	buf := bufferPool.Get().(*buffer)
+	buf.b = appendMetric(buf.b[:0], m)
+	f.Write(buf.b)
+	bufferPool.Put(buf)
+}
+
+type buffer struct {
+	b []byte
+}
+
+var bufferPool = sync.Pool{
+	New: func() interface{} { return &buffer{make([]byte, 0, 512)} },
+}

datadog/metric_test.go

@@ -1,6 +1,10 @@
 package datadog
 
-import "github.com/segmentio/stats"
+import (
+	"testing"
+
+	"github.com/segmentio/stats"
+)
 
 var testMetrics = []struct {
 	s string
@@ -116,3 +120,13 @@ var testMetrics = []struct {
 		},
 	},
 }
+
+func TestMetricString(t *testing.T) {
+	for _, test := range testMetrics {
+		t.Run(test.s, func(t *testing.T) {
+			if s := test.m.String(); s != test.s {
+				t.Error(s)
+			}
+		})
+	}
+}