fix(common.socket): Use read buffer size config setting as a datagram reader buffer size (#16156)

plugins/common/socket/datagram.go

@@ -49,7 +49,7 @@ func (l *packetListener) listenData(onData CallbackData, onError CallbackError)
 	go func() {
 		defer l.wg.Done()
 
-		buf := make([]byte, 64*1024) // 64kb - maximum size of IP packet
+		buf := make([]byte, l.ReadBufferSize)
 		for {
 			n, src, err := l.conn.ReadFrom(buf)
 			receiveTime := time.Now()
@@ -88,7 +88,7 @@ func (l *packetListener) listenConnection(onConnection CallbackConnection, onErr
 		defer l.wg.Done()
 		defer l.conn.Close()
 
-		buf := make([]byte, 64*1024) // 64kb - maximum size of IP packet
+		buf := make([]byte, l.ReadBufferSize)
 		for {
 			// Wait for packets and read them
 			n, src, err := l.conn.ReadFrom(buf)
@@ -133,7 +133,7 @@ func (l *packetListener) listenConnection(onConnection CallbackConnection, onErr
 	}()
 }
 
-func (l *packetListener) setupUnixgram(u *url.URL, socketMode string) error {
+func (l *packetListener) setupUnixgram(u *url.URL, socketMode string, bufferSize int) error {
 	l.path = filepath.FromSlash(u.Path)
 	if runtime.GOOS == "windows" && strings.Contains(l.path, ":") {
 		l.path = strings.TrimPrefix(l.path, `\`)
@@ -162,6 +162,12 @@ func (l *packetListener) setupUnixgram(u *url.URL, socketMode string) error {
 		}
 	}
 
+	if bufferSize > 0 {
+		l.ReadBufferSize = bufferSize
+	} else {
+		l.ReadBufferSize = 64 * 1024 // 64kb - IP packet size
+	}
+
 	return l.setupDecoder()
 }
 
@@ -198,6 +204,7 @@ func (l *packetListener) setupUDP(u *url.URL, ifname string, bufferSize int) err
 		}
 	}
 
+	l.ReadBufferSize = 64 * 1024 // 64kb - IP packet size
 	l.conn = conn
 	return l.setupDecoder()
 }
@@ -208,6 +215,7 @@ func (l *packetListener) setupIP(u *url.URL) error {
 		return fmt.Errorf("listening (ip) failed: %w", err)
 	}
 
+	l.ReadBufferSize = 64 * 1024 // 64kb - IP packet size
 	l.conn = conn
 	return l.setupDecoder()
 }

plugins/common/socket/socket.go

@@ -136,7 +136,7 @@ func (s *Socket) Setup() error {
 		s.listener = l
 	case "unixgram":
 		l := newPacketListener(s.ContentEncoding, s.MaxDecompressionSize, s.MaxParallelParsers)
-		if err := l.setupUnixgram(s.url, s.SocketMode); err != nil {
+		if err := l.setupUnixgram(s.url, s.SocketMode, int(s.ReadBufferSize)); err != nil {
 			return err
 		}
 		s.listener = l

plugins/inputs/socket_listener/socket_listener_test.go

@@ -197,8 +197,8 @@ func TestSocketListener(t *testing.T) {
 	}
 }
 
-func TestLargeReadBuffer(t *testing.T) {
+func TestLargeReadBufferTCP(t *testing.T) {
-	// Construct a buffer-size setting of 100KiB
+	// Construct a buffer-size setting of 1000KiB
 	var bufsize config.Size
 	require.NoError(t, bufsize.UnmarshalText([]byte("1000KiB")))
 
@@ -262,6 +262,92 @@ func TestLargeReadBuffer(t *testing.T) {
 	testutil.RequireMetricsEqual(t, expected, actual, testutil.IgnoreTime())
 }
 
+func TestLargeReadBufferUnixgram(t *testing.T) {
+	// Construct a buffer-size setting of 100KiB
+	// Assuming that the testing environment has net.core.wmem_max set to a value greater than 100KiB
+	if runtime.GOOS == "windows" {
+		t.Skip("Skipping on Windows, as unixgram sockets are not supported")
+	}
+
+	if runtime.GOOS == "darwin" {
+		t.Skip("Skipping on macOS (darwin), as unixgram write buffer size cannot be changed (default 2048 bytes)")
+	}
+
+	var bufsize config.Size
+	require.NoError(t, bufsize.UnmarshalText([]byte("100KiB")))
+
+	// Create a socket
+	sock, err := os.CreateTemp("", "sock-")
+	require.NoError(t, err)
+	defer sock.Close()
+	defer os.Remove(sock.Name())
+	var serverAddr = sock.Name()
+
+	// Setup plugin with a sufficient read buffer
+	plugin := &SocketListener{
+		ServiceAddress: "unixgram" + "://" + serverAddr,
+		Config: socket.Config{
+			ReadBufferSize: bufsize,
+		},
+		Log: &testutil.Logger{},
+	}
+	parser := &value.Parser{
+		MetricName: "test",
+		DataType:   "string",
+	}
+	require.NoError(t, parser.Init())
+	plugin.SetParser(parser)
+
+	// Create a large message with the readbuffer size
+	message := bytes.Repeat([]byte{'a'}, int(bufsize))
+	expected := []telegraf.Metric{
+		metric.New(
+			"test",
+			map[string]string{},
+			map[string]interface{}{"value": string(message)},
+			time.Unix(0, 0),
+		),
+	}
+
+	// Start the plugin
+	var acc testutil.Accumulator
+	require.NoError(t, plugin.Init())
+	require.NoError(t, plugin.Start(&acc))
+	defer plugin.Stop()
+
+	addr := plugin.socket.Address()
+
+	// Setup the client for submitting data
+	client, err := createClient(plugin.ServiceAddress, addr, nil)
+	require.NoError(t, err)
+	defer client.Close()
+
+	// Check the socket write buffer size
+	unixConn, ok := client.(*net.UnixConn)
+	require.True(t, ok, "client is not a *net.UnixConn")
+	if err := unixConn.SetWriteBuffer(len(message)); err != nil {
+		t.Skipf("Failed to set write buffer size: %v. Skipping test.", err)
+	}
+
+	// Write the message
+	_, err = client.Write(message)
+	require.NoError(t, err)
+	client.Close()
+
+	getError := func() error {
+		acc.Lock()
+		defer acc.Unlock()
+		return acc.FirstError()
+	}
+
+	// Test the resulting metrics and compare against expected results
+	require.Eventuallyf(t, func() bool {
+		return acc.NMetrics() >= uint64(len(expected))
+	}, time.Second, 100*time.Millisecond, "did not receive metrics (%d): %v", acc.NMetrics(), getError())
+	actual := acc.GetTelegrafMetrics()
+	testutil.RequireMetricsEqual(t, expected, actual, testutil.IgnoreTime())
+}
+
 func TestCases(t *testing.T) {
 	// Get all directories in testdata
 	folders, err := os.ReadDir("testcases")