Use Random port for listener in collector ext (#1751)

Author: vasireddy99

collector/internal/telemetryapi/listener.go

@@ -17,18 +17,32 @@ package telemetryapi
 import (
 	"context"
 	"encoding/json"
+	"errors"
 	"fmt"
 	"io"
+	"math/rand"
+	"net"
 	"net/http"
 	"os"
+	"syscall"
 	"time"
 
 	"github.com/golang-collections/go-datastructures/queue"
 	"go.uber.org/zap"
 )
 
-const defaultListenerPort = "53612"
-const initialQueueSize = 5
+const (
+	initialQueueSize = 5
+	maxRetries       = 5
+	// Define ephemeral port range (typical range is 49152-65535)
+	minPort = 49152
+	maxPort = 65535
+)
+
+// getRandomPort returns a random port number within the ephemeral range
+func getRandomPort() string {
+	return fmt.Sprintf("%d", rand.Intn(maxPort-minPort)+minPort)
+}
 
 // Listener is used to listen to the Telemetry API
 type Listener struct {
@@ -46,26 +60,48 @@ func NewListener(logger *zap.Logger) *Listener {
 	}
 }
 
-func listenOnAddress() string {
+func (s *Listener) tryBindPort() (net.Listener, string, error) {
+	for i := 0; i < maxRetries; i++ {
+		port := getRandomPort()
+		address := listenOnAddress(port)
+
+		l, err := net.Listen("tcp", address)
+		if err != nil {
+			if errors.Is(err, syscall.EADDRINUSE) {
+				s.logger.Debug("Port in use, trying another",
+					zap.String("address", address))
+				continue
+			}
+			return nil, "", err
+		}
+		return l, address, nil
+	}
+
+	return nil, "", fmt.Errorf("failed to find available port after %d attempts", maxRetries)
+}
+
+func listenOnAddress(port string) string {
 	envAwsLocal, ok := os.LookupEnv("AWS_SAM_LOCAL")
 	var addr string
 	if ok && envAwsLocal == "true" {
-		addr = ":" + defaultListenerPort
+		addr = ":" + port
 	} else {
-		addr = "sandbox.localdomain:" + defaultListenerPort
+		addr = "sandbox.localdomain:" + port
 	}
-
 	return addr
 }
 
 // Start the server in a goroutine where the log events will be sent
 func (s *Listener) Start() (string, error) {
-	address := listenOnAddress()
+	listener, address, err := s.tryBindPort()
+	if err != nil {
+		return "", fmt.Errorf("failed to find available port: %w", err)
+	}
 	s.logger.Info("Listening for requests", zap.String("address", address))
 	s.httpServer = &http.Server{Addr: address}
 	http.HandleFunc("/", s.httpHandler)
 	go func() {
-		err := s.httpServer.ListenAndServe()
+		err := s.httpServer.Serve(listener)
 		if err != http.ErrServerClosed {
 			s.logger.Error("Unexpected stop on HTTP Server", zap.Error(err))
 			s.Shutdown()