Reduce UDP service per-packet allocation size

This will reduce memory pressure and number of GC cycles, my results
sending 100,000 UDP points were:

- udp-payload-size=0: 242 GC cycles
- udp-payload-size=1500: 142 GC cycles
- udp-payload-size=0 (with change): 114 GC cycles
- udp-payload-size=1500 (with change): 112 GC cycles

CHANGELOG.md

@@ -3,6 +3,7 @@
 ### Features
 
 - [#6237](https://github.com/influxdata/influxdb/issues/6237): Enable continuous integration testing on Windows platform via AppVeyor. Thanks @mvadu
+- [#6263](https://github.com/influxdata/influxdb/pull/6263): Reduce UDP Service allocation size.
 
 ### Bugfixes
 

services/udp/config.go

@@ -40,24 +40,6 @@ const (
 	//     Linux:      sudo sysctl -w net.core.rmem_max=<read-buffer>
 	//     BSD/Darwin: sudo sysctl -w kern.ipc.maxsockbuf=<read-buffer>
 	DefaultReadBuffer = 0
-
-	// DefaultUDPPayloadSize sets the default value of the incoming UDP packet
-	// to the spec max, i.e. 65536. That being said, this value should likely
-	// be tuned lower to match your udp_payload size if using tools like
-	// telegraf.
-	//
-	// https://en.wikipedia.org/wiki/User_Datagram_Protocol#Packet_structure
-	//
-	// Reading packets from a UDP socket in go actually only pulls
-	// one packet at a time, requiring a very fast reader to keep up with
-	// incoming data at scale. Reducing the overhead of the expected packet
-	// helps allocate memory faster (~10-25µs --> ~150ns with go1.5.2), thereby
-	// speeding up the processing of data coming in.
-	//
-	// NOTE: if you send a payload greater than the UDPPayloadSize, you will
-	// cause a buffer overflow...tune your application very carefully to match
-	// udp_payload for your metrics source
-	DefaultUDPPayloadSize = 65536
 )
 
 // Config holds various configuration settings for the UDP listener.
@@ -72,7 +54,9 @@ type Config struct {
 	ReadBuffer      int           `toml:"read-buffer"`
 	BatchTimeout    toml.Duration `toml:"batch-timeout"`
 	Precision       string        `toml:"precision"`
-	UDPPayloadSize  int           `toml:"udp-payload-size"`
+
+	// Deprecated config option
+	udpPayloadSize int `toml:"udp-payload-size"`
 }
 
 // NewConfig returns a new instance of Config with defaults.
@@ -109,8 +93,5 @@ func (c *Config) WithDefaults() *Config {
 	if d.ReadBuffer == 0 {
 		d.ReadBuffer = DefaultReadBuffer
 	}
-	if d.UDPPayloadSize == 0 {
-		d.UDPPayloadSize = DefaultUDPPayloadSize
-	}
 	return &d
 }

services/udp/config_test.go

@@ -39,7 +39,5 @@ udp-payload-size = 1500
 		t.Fatalf("unexpected batch pending: %d", c.BatchPending)
 	} else if time.Duration(c.BatchTimeout) != (10 * time.Millisecond) {
 		t.Fatalf("unexpected batch timeout: %v", c.BatchTimeout)
-	} else if c.UDPPayloadSize != 1500 {
-		t.Fatalf("unexpected udp-payload-size: %d", c.UDPPayloadSize)
 	}
 }

services/udp/service.go

@@ -19,6 +19,8 @@ import (
 const (
 	// Arbitrary, testing indicated that this doesn't typically get over 10
 	parserChanLen = 1000
+
+	MAX_UDP_PAYLOAD = 64 * 1024
 )
 
 // statistics gathered by the UDP package.
@@ -144,6 +146,7 @@ func (s *Service) writer() {
 func (s *Service) serve() {
 	defer s.wg.Done()
 
+	buf := make([]byte, MAX_UDP_PAYLOAD)
 	s.batcher.Start()
 	for {
 
@@ -153,15 +156,17 @@ func (s *Service) serve() {
 			return
 		default:
 			// Keep processing.
-			buf := make([]byte, s.config.UDPPayloadSize)
 			n, _, err := s.conn.ReadFromUDP(buf)
 			if err != nil {
 				s.statMap.Add(statReadFail, 1)
 				s.Logger.Printf("Failed to read UDP message: %s", err)
 				continue
 			}
 			s.statMap.Add(statBytesReceived, int64(n))
-			s.parserChan <- buf[:n]
+
+			bufCopy := make([]byte, n)
+			copy(bufCopy, buf[:n])
+			s.parserChan <- bufCopy
 		}
 	}
 }