refresh udp ip at some cadence

CHANGELOG.md

@@ -6,6 +6,7 @@
 
 - [FEATURE] Add `WithMaxSamplesPerContext()` option to limit the number of samples per context. See [#292][].
 - [BUGFIX] Fix the `rate` of distributions and histograms when using client side aggregation. See [#283][].
+- [FEATURE] Add `WithUDPAddrRefreshRate(rate time.Duration)` option to refresh the UDP address at a given interval. See [#280][].
 
 # 5.3.0 / 2023-03-06
 

statsd/options.go

@@ -27,6 +27,7 @@ var (
 	defaultOriginDetection              = true
 	defaultChannelModeErrorsWhenFull    = false
 	defaultErrorHandler                 = func(error) {}
+	defaultUDPAddrRefreshRate           = 0 * time.Second
 )
 
 // Options contains the configuration options for a client.
@@ -52,6 +53,7 @@ type Options struct {
 	containerID                  string
 	channelModeErrorsWhenFull    bool
 	errorHandler                 ErrorHandler
+	udpAddrRefreshRate           time.Duration
 }
 
 func resolveOptions(options []Option) (*Options, error) {
@@ -75,6 +77,7 @@ func resolveOptions(options []Option) (*Options, error) {
 		originDetection:              defaultOriginDetection,
 		channelModeErrorsWhenFull:    defaultChannelModeErrorsWhenFull,
 		errorHandler:                 defaultErrorHandler,
+		udpAddrRefreshRate:           defaultUDPAddrRefreshRate,
 	}
 
 	for _, option := range options {
@@ -396,3 +399,13 @@ func WithContainerID(id string) Option {
 		return nil
 	}
 }
+
+// WithUDPAddrRefreshRate sets the interval at which the client refreshes the UDP address.
+// This is useful when using the Agent's address may change during deployments without a fixed IP.
+// A value of 0 disables the refresh.
+func WithUDPAddrRefreshRate(rate time.Duration) Option {
+	return func(o *Options) error {
+		o.udpAddrRefreshRate = rate
+		return nil
+	}
+}

statsd/statsd.go

@@ -363,7 +363,7 @@ func parseAgentURL(agentURL string) string {
 	return ""
 }
 
-func createWriter(addr string, writeTimeout time.Duration) (io.WriteCloser, string, error) {
+func createWriter(addr string, writeTimeout time.Duration, udpAddrRefreshRate time.Duration) (io.WriteCloser, string, error) {
 	addr = resolveAddr(addr)
 	if addr == "" {
 		return nil, "", errors.New("No address passed and autodetection from environment failed")
@@ -383,7 +383,7 @@ func createWriter(addr string, writeTimeout time.Duration) (io.WriteCloser, stri
 		w, err := newUDSWriter(addr[len(UnixAddressStreamPrefix):], writeTimeout, "unix")
 		return w, writerNameUDS, err
 	default:
-		w, err := newUDPWriter(addr, writeTimeout)
+		w, err := newUDPWriter(addr, writeTimeout, udpAddrRefreshRate)
 		return w, writerNameUDP, err
 	}
 }
@@ -396,7 +396,7 @@ 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.udpAddrRefreshRate)
 	if err != nil {
 		return nil, err
 	}
@@ -527,7 +527,7 @@ func newWithWriter(w io.WriteCloser, o *Options, writerName string) (*Client, er
 			c.telemetryClient = newTelemetryClient(&c, writerName, c.agg != nil)
 		} else {
 			var err error
-			c.telemetryClient, err = newTelemetryClientWithCustomAddr(&c, writerName, o.telemetryAddr, c.agg != nil, bufferPool, o.writeTimeout)
+			c.telemetryClient, err = newTelemetryClientWithCustomAddr(&c, writerName, o.telemetryAddr, c.agg != nil, bufferPool, o.writeTimeout, o.udpAddrRefreshRate)
 			if err != nil {
 				return nil, err
 			}

statsd/telemetry.go

@@ -139,8 +139,8 @@ func newTelemetryClient(c *Client, transport string, aggregationEnabled bool) *t
 	return t
 }
 
-func newTelemetryClientWithCustomAddr(c *Client, transport string, telemetryAddr string, aggregationEnabled bool, pool *bufferPool, writeTimeout time.Duration) (*telemetryClient, error) {
-	telemetryWriter, _, err := createWriter(telemetryAddr, writeTimeout)
+func newTelemetryClientWithCustomAddr(c *Client, transport string, telemetryAddr string, aggregationEnabled bool, pool *bufferPool, writeTimeout time.Duration, udpAddrRefreshRate time.Duration) (*telemetryClient, error) {
+	telemetryWriter, _, err := createWriter(telemetryAddr, writeTimeout, udpAddrRefreshRate)
 	if err != nil {
 		return nil, fmt.Errorf("Could not resolve telemetry address: %v", err)
 	}

statsd/udp.go

@@ -2,33 +2,80 @@ package statsd
 
 import (
 	"net"
+	"sync"
 	"time"
 )
 
 // udpWriter is an internal class wrapping around management of UDP connection
 type udpWriter struct {
-	conn net.Conn
+	conn   net.PacketConn
+	addr   string
+	dst    *dstValue
+	closed chan struct{}
+}
+
+type dstValue struct {
+	mutex sync.RWMutex
+	dst   *net.UDPAddr
+}
+
+func (d *dstValue) set(dst *net.UDPAddr) {
+	d.mutex.Lock()
+	defer d.mutex.Unlock()
+	d.dst = dst
+}
+
+func (d *dstValue) get() *net.UDPAddr {
+	d.mutex.RLock()
+	defer d.mutex.RUnlock()
+	return d.dst
 }
 
 // New returns a pointer to a new udpWriter given an addr in the format "hostname:port".
-func newUDPWriter(addr string, _ time.Duration) (*udpWriter, error) {
-	udpAddr, err := net.ResolveUDPAddr("udp", addr)
+func newUDPWriter(addr string, _ time.Duration, refreshRate time.Duration) (*udpWriter, error) {
+	conn, err := net.ListenPacket("udp", ":0")
 	if err != nil {
 		return nil, err
 	}
-	conn, err := net.DialUDP("udp", nil, udpAddr)
+	currentDst, err := getCurrentDst(addr)
 	if err != nil {
 		return nil, err
 	}
-	writer := &udpWriter{conn: conn}
+	dst := &dstValue{dst: currentDst}
+	writer := &udpWriter{conn: conn, addr: addr, dst: dst, closed: make(chan struct{})}
+	if refreshRate > 0 {
+		go writer.refreshDstLoop(refreshRate)
+	}
 	return writer, nil
 }
 
+func (w *udpWriter) refreshDstLoop(refreshRate time.Duration) {
+	ticker := time.NewTicker(refreshRate)
+	defer ticker.Stop()
+	for {
+		select {
+		case <-w.closed:
+			return
+		case <-ticker.C:
+			dst, err := getCurrentDst(w.addr)
+			if err != nil {
+				continue
+			}
+			w.dst.set(dst)
+		}
+	}
+}
+
 // Write data to the UDP connection with no error handling
 func (w *udpWriter) Write(data []byte) (int, error) {
-	return w.conn.Write(data)
+	return w.conn.WriteTo(data, w.dst.get())
 }
 
 func (w *udpWriter) Close() error {
+	close(w.closed)
 	return w.conn.Close()
 }
+
+func getCurrentDst(addr string) (*net.UDPAddr, error) {
+	return net.ResolveUDPAddr("udp", addr)
+}