Add a signal handler to allow clean up of unixgram socket file

Signed-off-by: Wangchong Zhou <fffonion@gmail.com>

exporter.go

@@ -652,7 +652,13 @@ func (l *StatsDUDPListener) Listen(e chan<- Events) {
 	for {
 		n, _, err := l.conn.ReadFromUDP(buf)
 		if err != nil {
-			log.Fatal(err)
+			// https://github.com/golang/go/issues/4373
+			// ignore net: errClosing error as it will occur during shutdown
+			if strings.HasSuffix(err.Error(), "use of closed network connection") {
+				return
+			}
+			log.Error(err)
+			return
 		}
 		l.handlePacket(buf[0:n], e)
 	}
@@ -677,6 +683,11 @@ func (l *StatsDTCPListener) Listen(e chan<- Events) {
 	for {
 		c, err := l.conn.AcceptTCP()
 		if err != nil {
+			// https://github.com/golang/go/issues/4373
+			// ignore net: errClosing error as it will occur during shutdown
+			if strings.HasSuffix(err.Error(), "use of closed network connection") {
+				return
+			}
 			log.Fatalf("AcceptTCP failed: %v", err)
 		}
 		go l.handleConn(c, e)
@@ -717,6 +728,11 @@ func (l *StatsDUnixgramListener) Listen(e chan<- Events) {
 	for {
 		n, _, err := l.conn.ReadFromUnix(buf)
 		if err != nil {
+			// https://github.com/golang/go/issues/4373
+			// ignore net: errClosing error as it will occur during shutdown
+			if strings.HasSuffix(err.Error(), "use of closed network connection") {
+				return
+			}
 			log.Fatal(err)
 		}
 		l.handlePacket(buf[:n], e)

main.go

@@ -18,7 +18,9 @@ import (
 	"net"
 	"net/http"
 	"os"
+	"os/signal"
 	"strconv"
+	"syscall"
 
 	"github.com/howeyc/fsnotify"
 	"github.com/prometheus/client_golang/prometheus"
@@ -199,7 +201,8 @@ func main() {
 	}
 
 	if *statsdListenUnixgram != "" {
-		if _, err := os.Stat(*statsdListenUnixgram); !os.IsNotExist(err) {
+		var err error
+		if _, err = os.Stat(*statsdListenUnixgram); !os.IsNotExist(err) {
 			log.Fatalf("Unixgram socket \"%s\" already exists", *statsdListenUnixgram)
 		}
 		uxgconn, err := net.ListenUnixgram("unixgram", &net.UnixAddr{
@@ -225,6 +228,8 @@ func main() {
 		// if it's an abstract unix domain socket, it won't exist on fs
 		// so we can't chmod it either
 		if _, err := os.Stat(*statsdListenUnixgram); !os.IsNotExist(err) {
+			defer os.Remove(*statsdListenUnixgram)
+
 			// convert the string to octet
 			perm, err := strconv.ParseInt("0"+string(*statsdUnixSocketMode), 8, 32)
 			if err != nil {
@@ -254,5 +259,11 @@ func main() {
 		go watchConfig(*mappingConfig, mapper)
 	}
 	exporter := NewExporter(mapper)
-	exporter.Listen(events)
+
+	signals := make(chan os.Signal)
+	signal.Notify(signals, os.Interrupt, syscall.SIGTERM)
+
+	go exporter.Listen(events)
+
+	<-signals
 }