Listen before leaving start in statsd (#5628)

plugins/inputs/statsd/statsd.go

@@ -13,11 +13,10 @@ import (
 	"sync"
 	"time"
 
-	"github.com/influxdata/telegraf/plugins/parsers/graphite"
-
 	"github.com/influxdata/telegraf"
 	"github.com/influxdata/telegraf/internal"
 	"github.com/influxdata/telegraf/plugins/inputs"
+	"github.com/influxdata/telegraf/plugins/parsers/graphite"
 	"github.com/influxdata/telegraf/selfstat"
 )
 
@@ -338,38 +337,64 @@ func (s *Statsd) Start(_ telegraf.Accumulator) error {
 		s.MetricSeparator = defaultSeparator
 	}
 
-	s.wg.Add(2)
-	// Start the UDP listener
 	if s.isUDP() {
-		go s.udpListen()
-	} else {
-		go s.tcpListen()
+		address, err := net.ResolveUDPAddr(s.Protocol, s.ServiceAddress)
+		if err != nil {
+			return err
 		}
+
+		conn, err := net.ListenUDP(s.Protocol, address)
+		if err != nil {
+			return err
+		}
+
+		log.Println("I! Statsd UDP listener listening on: ", conn.LocalAddr().String())
+		s.UDPlistener = conn
+
+		s.wg.Add(1)
+		go func() {
+			defer s.wg.Done()
+			s.udpListen(conn)
+		}()
+	} else {
+		address, err := net.ResolveTCPAddr("tcp", s.ServiceAddress)
+		if err != nil {
+			return err
+		}
+		listener, err := net.ListenTCP("tcp", address)
+		if err != nil {
+			return err
+		}
+
+		log.Println("I! TCP Statsd listening on: ", listener.Addr().String())
+		s.TCPlistener = listener
+
+		s.wg.Add(1)
+		go func() {
+			defer s.wg.Done()
+			s.tcpListen(listener)
+		}()
+	}
+
 	// Start the line parser
-	go s.parser()
+	s.wg.Add(1)
+	go func() {
+		defer s.wg.Done()
+		s.parser()
+	}()
 	log.Printf("I! Started the statsd service on %s\n", s.ServiceAddress)
 	return nil
 }
 
 // tcpListen() starts listening for udp packets on the configured port.
-func (s *Statsd) tcpListen() error {
-	defer s.wg.Done()
-	// Start listener
-	var err error
-	address, _ := net.ResolveTCPAddr("tcp", s.ServiceAddress)
-	s.TCPlistener, err = net.ListenTCP("tcp", address)
-	if err != nil {
-		log.Fatalf("ERROR: ListenTCP - %s", err)
-		return err
-	}
-	log.Println("I! TCP Statsd listening on: ", s.TCPlistener.Addr().String())
+func (s *Statsd) tcpListen(listener *net.TCPListener) error {
 	for {
 		select {
 		case <-s.done:
 			return nil
 		default:
 			// Accept connection:
-			conn, err := s.TCPlistener.AcceptTCP()
+			conn, err := listener.AcceptTCP()
 			if err != nil {
 				return err
 			}
@@ -403,16 +428,7 @@ func (s *Statsd) tcpListen() error {
 }
 
 // udpListen starts listening for udp packets on the configured port.
-func (s *Statsd) udpListen() error {
-	defer s.wg.Done()
-	var err error
-	address, _ := net.ResolveUDPAddr(s.Protocol, s.ServiceAddress)
-	s.UDPlistener, err = net.ListenUDP(s.Protocol, address)
-	if err != nil {
-		log.Fatalf("ERROR: ListenUDP - %s", err)
-	}
-	log.Println("I! Statsd UDP listener listening on: ", s.UDPlistener.LocalAddr().String())
-
+func (s *Statsd) udpListen(conn *net.UDPConn) error {
 	if s.ReadBufferSize > 0 {
 		s.UDPlistener.SetReadBuffer(s.ReadBufferSize)
 	}
@@ -423,7 +439,7 @@ func (s *Statsd) udpListen() error {
 		case <-s.done:
 			return nil
 		default:
-			n, _, err := s.UDPlistener.ReadFromUDP(buf)
+			n, _, err := conn.ReadFromUDP(buf)
 			if err != nil && !strings.Contains(err.Error(), "closed network") {
 				log.Printf("E! Error READ: %s\n", err.Error())
 				continue
@@ -448,7 +464,6 @@ func (s *Statsd) udpListen() error {
 // packet into statsd strings and then calls parseStatsdLine, which parses a
 // single statsd metric into a struct.
 func (s *Statsd) parser() error {
-	defer s.wg.Done()
 	for {
 		select {
 		case <-s.done: