Copy metrics for each configured output

This is for better thread-safety when running with multiple outputs,
which can cause very odd panics at very high loads

primarily this is to address #1432

closes #1432

plugins/inputs/tcp_listener/tcp_listener.go

@@ -31,6 +31,8 @@ type TcpListener struct {
 	accept chan bool
 	// drops tracks the number of dropped metrics.
 	drops int
+	// malformed tracks the number of malformed packets
+	malformed int
 
 	// track the listener here so we can close it in Stop()
 	listener *net.TCPListener
@@ -45,6 +47,9 @@ var dropwarn = "ERROR: tcp_listener message queue full. " +
 	"We have dropped %d messages so far. " +
 	"You may want to increase allowed_pending_messages in the config\n"
 
+var malformedwarn = "WARNING: tcp_listener has received %d malformed packets" +
+	" thus far."
+
 const sampleConfig = `
   ## Address and port to host TCP listener on
   service_address = ":8094"
@@ -243,8 +248,10 @@ func (t *TcpListener) tcpParser() error {
 			if err == nil {
 				t.storeMetrics(metrics)
 			} else {
-				log.Printf("Malformed packet: [%s], Error: %s\n",
-					string(packet), err)
+				t.malformed++
+				if t.malformed == 1 || t.malformed%1000 == 0 {
+					log.Printf(malformedwarn, t.malformed)
+				}
 			}
 		}
 	}

plugins/inputs/udp_listener/udp_listener.go

@@ -27,6 +27,8 @@ type UdpListener struct {
 	done chan struct{}
 	// drops tracks the number of dropped metrics.
 	drops int
+	// malformed tracks the number of malformed packets
+	malformed int
 
 	parser parsers.Parser
 
@@ -44,6 +46,9 @@ var dropwarn = "ERROR: udp_listener message queue full. " +
 	"We have dropped %d messages so far. " +
 	"You may want to increase allowed_pending_messages in the config\n"
 
+var malformedwarn = "WARNING: udp_listener has received %d malformed packets" +
+	" thus far."
+
 const sampleConfig = `
   ## Address and port to host UDP listener on
   service_address = ":8092"
@@ -152,7 +157,10 @@ func (u *UdpListener) udpParser() error {
 			if err == nil {
 				u.storeMetrics(metrics)
 			} else {
-				log.Printf("Malformed packet: [%s], Error: %s\n", packet, err)
+				u.malformed++
+				if u.malformed == 1 || u.malformed%1000 == 0 {
+					log.Printf(malformedwarn, u.malformed)
+				}
 			}
 		}
 	}

plugins/serializers/graphite/graphite.go

@@ -20,7 +20,7 @@ type GraphiteSerializer struct {
 	Template string
 }
 
-func (s GraphiteSerializer) Serialize(metric telegraf.Metric) ([]string, error) {
+func (s *GraphiteSerializer) Serialize(metric telegraf.Metric) ([]string, error) {
 	out := []string{}
 
 	// Convert UnixNano to Unix timestamps