add counter for dropped UDP packets. Remove unnecessary and misleading comment

Signed-off-by: kullanici0606 <yakup.turgut@btk.gov.tr>

bridge_test.go

@@ -543,6 +543,7 @@ func TestHandlePacket(t *testing.T) {
 		Logger:          log.NewNopLogger(),
 		LineParser:      parser,
 		UDPPackets:      udpPackets,
+		UDPPacketDrops:  udpPacketDrops,
 		LinesReceived:   linesReceived,
 		EventsFlushed:   eventsFlushed,
 		SampleErrors:    *sampleErrors,

main.go

@@ -71,6 +71,12 @@ var (
 			Help: "The total number of StatsD packets received over UDP.",
 		},
 	)
+	udpPacketDrops = promauto.NewCounter(
+		prometheus.CounterOpts{
+			Name: "statsd_exporter_udp_packet_drops_total",
+			Help: "The total number of dropped StatsD packets which received over UDP.",
+		},
+	)
 	tcpConnections = promauto.NewCounter(
 		prometheus.CounterOpts{
 			Name: "statsd_exporter_tcp_connections_total",
@@ -377,6 +383,7 @@ func main() {
 			Logger:          logger,
 			LineParser:      parser,
 			UDPPackets:      udpPackets,
+			UDPPacketDrops:  udpPacketDrops,
 			LinesReceived:   linesReceived,
 			EventsFlushed:   eventsFlushed,
 			Relay:           relayTarget,

pkg/exporter/exporter_test.go

@@ -56,6 +56,12 @@ var (
 			Help: "The total number of StatsD packets received over UDP.",
 		},
 	)
+	udpPacketDrops = prometheus.NewCounter(
+		prometheus.CounterOpts{
+			Name: "statsd_exporter_udp_packet_drops_total",
+			Help: "The total number of dropped StatsD packets which received over UDP.",
+		},
+	)
 	tcpConnections = prometheus.NewCounter(
 		prometheus.CounterOpts{
 			Name: "statsd_exporter_tcp_connections_total",
@@ -683,6 +689,7 @@ func TestInvalidUtf8InDatadogTagValue(t *testing.T) {
 			Logger:          log.NewNopLogger(),
 			LineParser:      parser,
 			UDPPackets:      udpPackets,
+			UDPPacketDrops:  udpPacketDrops,
 			LinesReceived:   linesReceived,
 			EventsFlushed:   eventsFlushed,
 			SampleErrors:    *sampleErrors,

pkg/listener/listener.go

@@ -38,6 +38,7 @@ type StatsDUDPListener struct {
 	Logger          log.Logger
 	LineParser      Parser
 	UDPPackets      prometheus.Counter
+	UDPPacketDrops  prometheus.Counter
 	LinesReceived   prometheus.Counter
 	EventsFlushed   prometheus.Counter
 	Relay           *relay.Relay
@@ -66,7 +67,7 @@ func (l *StatsDUDPListener) Listen() {
 			level.Error(l.Logger).Log("error", err)
 			return
 		}
-		// avoid making copies of slices since we need to minimize the time spent here in order not to drop packets
+
 		l.EnqueueUdpPacket(buf, n)
 	}
 }
@@ -75,7 +76,12 @@ func (l *StatsDUDPListener) EnqueueUdpPacket(packet []byte, n int) {
 	l.UDPPackets.Inc()
 	packetCopy := make([]byte, n)
 	copy(packetCopy, packet)
-	l.UdpPacketQueue <- packetCopy
+	select {
+	case l.UdpPacketQueue <- packetCopy:
+		// do nothing
+	default:
+		l.UDPPacketDrops.Inc()
+	}
 }
 
 func (l *StatsDUDPListener) ProcessUdpPacketQueue() {