uds: implement a connect timeout option

This is similar to DataDog/java-dogstatsd-client#228

statsd/options.go

@@ -17,6 +17,7 @@ var (
 	defaultWorkerCount                  = 32
 	defaultSenderQueueSize              = 0
 	defaultWriteTimeout                 = 100 * time.Millisecond
+	defaultConnectTimeout               = 1000 * time.Millisecond
 	defaultTelemetry                    = true
 	defaultReceivingMode                = mutexMode
 	defaultChannelModeBufferSize        = 4096
@@ -40,6 +41,7 @@ type Options struct {
 	workersCount                 int
 	senderQueueSize              int
 	writeTimeout                 time.Duration
+	connectTimeout               time.Duration
 	telemetry                    bool
 	receiveMode                  receivingMode
 	channelModeBufferSize        int
@@ -65,6 +67,7 @@ func resolveOptions(options []Option) (*Options, error) {
 		workersCount:                 defaultWorkerCount,
 		senderQueueSize:              defaultSenderQueueSize,
 		writeTimeout:                 defaultWriteTimeout,
+		connectTimeout:               defaultConnectTimeout,
 		telemetry:                    defaultTelemetry,
 		receiveMode:                  defaultReceivingMode,
 		channelModeBufferSize:        defaultChannelModeBufferSize,
@@ -206,6 +209,16 @@ func WithWriteTimeout(writeTimeout time.Duration) Option {
 	}
 }
 
+// WithConnectTimeout sets the timeout for network connection with the Agent, after this interval the connection
+// attempt is aborted. This is only used for UDS connection. This will also reset the connection if nothing can be
+// written to it for this duration.
+func WithConnectTimeout(connectTimeout time.Duration) Option {
+	return func(o *Options) error {
+		o.connectTimeout = connectTimeout
+		return nil
+	}
+}
+
 // WithChannelMode make the client use channels to receive metrics
 //
 // This determines how the client receive metrics from the app (for example when calling the `Gauge()` method).

statsd/statsd.go

@@ -368,7 +368,7 @@ func parseAgentURL(agentURL string) string {
 	return ""
 }
 
-func createWriter(addr string, writeTimeout time.Duration) (Transport, string, error) {
+func createWriter(addr string, writeTimeout time.Duration, connectTimeout time.Duration) (Transport, string, error) {
 	addr = resolveAddr(addr)
 	if addr == "" {
 		return nil, "", errors.New("No address passed and autodetection from environment failed")
@@ -379,13 +379,13 @@ func createWriter(addr string, writeTimeout time.Duration) (Transport, string, e
 		w, err := newWindowsPipeWriter(addr, writeTimeout)
 		return w, writerWindowsPipe, err
 	case strings.HasPrefix(addr, UnixAddressPrefix):
-		w, err := newUDSWriter(addr[len(UnixAddressPrefix):], writeTimeout, "")
+		w, err := newUDSWriter(addr[len(UnixAddressPrefix):], writeTimeout, connectTimeout, "")
 		return w, writerNameUDS, err
 	case strings.HasPrefix(addr, UnixAddressDatagramPrefix):
-		w, err := newUDSWriter(addr[len(UnixAddressDatagramPrefix):], writeTimeout, "unixgram")
+		w, err := newUDSWriter(addr[len(UnixAddressDatagramPrefix):], writeTimeout, connectTimeout, "unixgram")
 		return w, writerNameUDS, err
 	case strings.HasPrefix(addr, UnixAddressStreamPrefix):
-		w, err := newUDSWriter(addr[len(UnixAddressStreamPrefix):], writeTimeout, "unix")
+		w, err := newUDSWriter(addr[len(UnixAddressStreamPrefix):], writeTimeout, connectTimeout, "unix")
 		return w, writerNameUDS, err
 	default:
 		w, err := newUDPWriter(addr, writeTimeout)
@@ -401,7 +401,7 @@ func New(addr string, options ...Option) (*Client, error) {
 		return nil, err
 	}
 
-	w, writerType, err := createWriter(addr, o.writeTimeout)
+	w, writerType, err := createWriter(addr, o.writeTimeout, o.connectTimeout)
 	if err != nil {
 		return nil, err
 	}
@@ -542,7 +542,7 @@ func newWithWriter(w Transport, o *Options, writerName string) (*Client, error)
 			c.telemetryClient = newTelemetryClient(&c, c.agg != nil)
 		} else {
 			var err error
-			c.telemetryClient, err = newTelemetryClientWithCustomAddr(&c, o.telemetryAddr, c.agg != nil, bufferPool, o.writeTimeout)
+			c.telemetryClient, err = newTelemetryClientWithCustomAddr(&c, o.telemetryAddr, c.agg != nil, bufferPool, o.writeTimeout, o.connectTimeout)
 			if err != nil {
 				return nil, err
 			}

statsd/telemetry.go

@@ -138,8 +138,10 @@ func newTelemetryClient(c *Client, aggregationEnabled bool) *telemetryClient {
 	return t
 }
 
-func newTelemetryClientWithCustomAddr(c *Client, telemetryAddr string, aggregationEnabled bool, pool *bufferPool, writeTimeout time.Duration) (*telemetryClient, error) {
-	telemetryWriter, _, err := createWriter(telemetryAddr, writeTimeout)
+func newTelemetryClientWithCustomAddr(c *Client, telemetryAddr string, aggregationEnabled bool, pool *bufferPool,
+	writeTimeout time.Duration, connectTimeout time.Duration,
+) (*telemetryClient, error) {
+	telemetryWriter, _, err := createWriter(telemetryAddr, writeTimeout, connectTimeout)
 	if err != nil {
 		return nil, fmt.Errorf("Could not resolve telemetry address: %v", err)
 	}

statsd/uds.go

@@ -21,13 +21,15 @@ type udsWriter struct {
 	conn net.Conn
 	// write timeout
 	writeTimeout time.Duration
-	sync.RWMutex // used to lock conn / writer can replace it
+	// connect timeout
+	connectTimeout time.Duration
+	sync.RWMutex   // used to lock conn / writer can replace it
 }
 
 // newUDSWriter returns a pointer to a new udsWriter given a socket file path as addr.
-func newUDSWriter(addr string, writeTimeout time.Duration, transport string) (*udsWriter, error) {
+func newUDSWriter(addr string, writeTimeout time.Duration, connectTimeout time.Duration, transport string) (*udsWriter, error) {
 	// Defer connection to first Write
-	writer := &udsWriter{addr: addr, transport: transport, conn: nil, writeTimeout: writeTimeout}
+	writer := &udsWriter{addr: addr, transport: transport, conn: nil, writeTimeout: writeTimeout, connectTimeout: connectTimeout}
 	return writer, nil
 }
 
@@ -43,56 +45,23 @@ func (w *udsWriter) GetTransportName() string {
 	}
 }
 
-// retryOnWriteErr returns true if we should retry writing after a write error
-func (w *udsWriter) retryOnWriteErr(err error, stream bool) bool {
-	// Never retry when using unixgram (to preserve the historical behavior)
-	if !stream {
-		return false
-	}
-	// Otherwise we retry on timeout because we might have written a partial packet
-	if networkError, ok := err.(net.Error); ok && networkError.Timeout() {
+func (w *udsWriter) shouldCloseConnection(err error, partialWrite bool) bool {
+	if err != nil && partialWrite {
+		// We can't recover from a partial write
 		return true
 	}
-	return false
-}
-
-func (w *udsWriter) shouldCloseConnection(err error) bool {
 	if err, isNetworkErr := err.(net.Error); err != nil && (!isNetworkErr || !err.Timeout()) {
 		// Statsd server disconnected, retry connecting at next packet
 		return true
 	}
 	return false
 }
 
-// writeFull writes the whole data to the UDS connection
-func (w *udsWriter) writeFull(data []byte, stopIfNoneWritten bool, stream bool) (int, error) {
-	written := 0
-	for written < len(data) {
-		n, e := w.conn.Write(data[written:])
-		written += n
-
-		// If we haven't written anything, and we're supposed to stop if we can't write anything, return the error
-		if written == 0 && stopIfNoneWritten {
-			return written, e
-		}
-
-		// If there's an error, check if it is retryable
-		if e != nil && !w.retryOnWriteErr(e, stream) {
-			return written, e
-		}
-
-		// When using "unix" we need to be able to finish to write partially written packets once we have started.
-		if stream {
-			w.conn.SetWriteDeadline(time.Time{})
-		}
-	}
-	return written, nil
-}
-
 // Write data to the UDS connection with write timeout and minimal error handling:
 // create the connection if nil, and destroy it if the statsd server has disconnected
 func (w *udsWriter) Write(data []byte) (int, error) {
 	var n int
+	partialWrite := false
 	conn, err := w.ensureConnection()
 	if err != nil {
 		return 0, err
@@ -107,15 +76,26 @@ func (w *udsWriter) Write(data []byte) (int, error) {
 	if stream {
 		bs := []byte{0, 0, 0, 0}
 		binary.LittleEndian.PutUint32(bs, uint32(len(data)))
-		_, err = w.writeFull(bs, true, true)
+		_, err = w.conn.Write(bs)
+
+		partialWrite = true
+
+		// W need to be able to finish to write partially written packets once we have started.
+		// But we will reset the connection if we can't write anything at all for a long time.
+		w.conn.SetWriteDeadline(time.Now().Add(w.connectTimeout))
+
+		// Continue writing only if we've written the length of the packet
 		if err == nil {
-			n, err = w.writeFull(data, false, true)
+			n, err = w.conn.Write(data)
+			if err == nil {
+				partialWrite = false
+			}
 		}
 	} else {
-		n, err = w.writeFull(data, true, false)
+		n, err = w.conn.Write(data)
 	}
 
-	if w.shouldCloseConnection(err) {
+	if w.shouldCloseConnection(err, partialWrite) {
 		w.unsetConnection()
 	}
 	return n, err
@@ -133,7 +113,7 @@ func (w *udsWriter) tryToDial(network string) (net.Conn, error) {
 	if err != nil {
 		return nil, err
 	}
-	newConn, err := net.Dial(udsAddr.Network(), udsAddr.String())
+	newConn, err := net.DialTimeout(udsAddr.Network(), udsAddr.String(), w.connectTimeout)
 	if err != nil {
 		return nil, err
 	}
@@ -182,5 +162,6 @@ func (w *udsWriter) ensureConnection() (net.Conn, error) {
 func (w *udsWriter) unsetConnection() {
 	w.Lock()
 	defer w.Unlock()
+	_ = w.conn.Close()
 	w.conn = nil
 }

statsd/uds_test.go

@@ -5,13 +5,14 @@ package statsd
 
 import (
 	"encoding/binary"
-	"golang.org/x/net/nettest"
 	"math/rand"
 	"net"
 	"os"
 	"testing"
 	"time"
 
+	"golang.org/x/net/nettest"
+
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
@@ -21,13 +22,13 @@ func init() {
 }
 
 func TestNewUDSWriter(t *testing.T) {
-	w, err := newUDSWriter("/tmp/test.socket", 100*time.Millisecond, "")
+	w, err := newUDSWriter("/tmp/test.socket", 100*time.Millisecond, 1000*time.Millisecond, "")
 	assert.NotNil(t, w)
 	assert.NoError(t, err)
-	w, err = newUDSWriter("/tmp/test.socket", 100*time.Millisecond, "unix")
+	w, err = newUDSWriter("/tmp/test.socket", 100*time.Millisecond, 1000*time.Millisecond, "unix")
 	assert.NotNil(t, w)
 	assert.NoError(t, err)
-	w, err = newUDSWriter("/tmp/test.socket", 100*time.Millisecond, "unixgram")
+	w, err = newUDSWriter("/tmp/test.socket", 100*time.Millisecond, 1000*time.Millisecond, "unixgram")
 	assert.NotNil(t, w)
 	assert.NoError(t, err)
 }
@@ -44,7 +45,7 @@ func TestUDSDatagramWrite(t *testing.T) {
 	err = os.Chmod(socketPath, 0722)
 	require.NoError(t, err)
 
-	w, err := newUDSWriter(socketPath, 100*time.Millisecond, "")
+	w, err := newUDSWriter(socketPath, 100*time.Millisecond, 1000*time.Millisecond, "")
 	require.Nil(t, err)
 	require.NotNil(t, w)
 
@@ -74,7 +75,7 @@ func TestUDSDatagramWriteUnsetConnection(t *testing.T) {
 	err = os.Chmod(socketPath, 0722)
 	require.NoError(t, err)
 
-	w, err := newUDSWriter(socketPath, 100*time.Millisecond, "")
+	w, err := newUDSWriter(socketPath, 100*time.Millisecond, 1000*time.Millisecond, "")
 	require.Nil(t, err)
 	require.NotNil(t, w)
 
@@ -107,7 +108,7 @@ func TestUDSStreamWrite(t *testing.T) {
 	err = os.Chmod(socketPath, 0722)
 	require.NoError(t, err)
 
-	w, err := newUDSWriter(socketPath, 100*time.Millisecond, "")
+	w, err := newUDSWriter(socketPath, 100*time.Millisecond, 1000*time.Millisecond, "")
 	require.Nil(t, err)
 	require.NotNil(t, w)
 
@@ -120,6 +121,7 @@ func TestUDSStreamWrite(t *testing.T) {
 		require.NoError(t, err)
 		assert.Equal(t, len(msg), n)
 
+		// This works because the kernel accepts sockets before the accept call
 		if conn == nil {
 			conn, err = listener.Accept()
 			require.NoError(t, err)
@@ -148,7 +150,7 @@ func TestUDSStreamWriteUnsetConnection(t *testing.T) {
 	err = os.Chmod(socketPath, 0722)
 	require.NoError(t, err)
 
-	w, err := newUDSWriter(socketPath, 100*time.Millisecond, "")
+	w, err := newUDSWriter(socketPath, 100*time.Millisecond, 1000*time.Millisecond, "")
 	require.Nil(t, err)
 	require.NotNil(t, w)
 
@@ -161,6 +163,7 @@ func TestUDSStreamWriteUnsetConnection(t *testing.T) {
 		require.NoError(t, err)
 		assert.Equal(t, len(msg), n)
 
+		// This works because the kernel accepts sockets before the accept call
 		if conn == nil {
 			conn, err = listener.Accept()
 			require.NoError(t, err)
@@ -180,3 +183,34 @@ func TestUDSStreamWriteUnsetConnection(t *testing.T) {
 		conn = nil
 	}
 }
+
+func TestUDSStreamPartialWrite(t *testing.T) {
+	socketPath, err := nettest.LocalPath()
+	require.NoError(t, err)
+	defer os.Remove(socketPath)
+
+	address, err := net.ResolveUnixAddr("unix", socketPath)
+	require.NoError(t, err)
+	listener, err := net.ListenUnix("unix", address)
+	defer listener.Close()
+	require.NoError(t, err)
+	err = os.Chmod(socketPath, 0722)
+	require.NoError(t, err)
+
+	w, err := newUDSWriter(socketPath, 100*time.Millisecond, 1000*time.Millisecond, "")
+	require.Nil(t, err)
+	require.NotNil(t, w)
+
+	// Force a connection
+	w.ensureConnection()
+	// Set a very low buffer size to force a partial write, but still enough to write the header
+	w.conn.(*net.UnixConn).SetWriteBuffer(8)
+
+	msg := []byte("some data")
+	n, err := w.Write(msg)
+	require.Error(t, err)
+	assert.Lessf(t, n, len(msg), "n: %d, len(msg): %d", n, len(msg))
+
+	// The connection should be dropped
+	assert.Nil(t, w.conn)
+}