Add support for port reuse by implementing multiplexing listener

config/configgrpc/configgrpc.go

@@ -165,6 +165,10 @@ type GRPCServerSettings struct {
 
 	// Auth for this receiver
 	Auth *configauth.Authentication `mapstructure:"auth,omitempty"`
+
+	// MuxListener is the multiplexing listener for the Endpoint of NetAddr. Through multiplexing, we can
+	// support many sockets on the same port with the same listener.
+	MuxListener net.Listener `mapstructure:"multiplexing_listener"`
 }
 
 // ToDialOptions maps configgrpc.GRPCClientSettings to a slice of dial options for gRPC
@@ -237,6 +241,15 @@ func validateBalancerName(balancerName string) bool {
 
 // ToListener returns the net.Listener constructed from the settings.
 func (gss *GRPCServerSettings) ToListener() (net.Listener, error) {
+	if gss.MuxListener != nil && strings.EqualFold(gss.NetAddr.Endpoint, gss.MuxListener.Addr().String()) {
+		return gss.MuxListener, nil
+	}
+	if gss.MuxListener != nil {
+		err := gss.MuxListener.Close()
+		if err != nil {
+			return nil, err
+		}
+	}
 	return gss.NetAddr.Listen()
 }
 

config/confighttp/confighttp.go

@@ -18,6 +18,7 @@ import (
 	"crypto/tls"
 	"net"
 	"net/http"
+	"strings"
 	"time"
 
 	"github.com/rs/cors"
@@ -123,13 +124,30 @@ type HTTPServerSettings struct {
 	// CORS needs to be enabled first by providing a non-empty list in CorsOrigins
 	// A wildcard (*) can be used to match any header.
 	CorsHeaders []string `mapstructure:"cors_allowed_headers"`
+
+	// MuxListener is the multiplexing listener for the Endpoint. Through multiplexing, we can
+	// support many sockets on the same port with the same listener.
+	MuxListener net.Listener `mapstructure:"multiplexing_listener"`
 }
 
 // ToListener creates a net.Listener.
 func (hss *HTTPServerSettings) ToListener() (net.Listener, error) {
-	listener, err := net.Listen("tcp", hss.Endpoint)
-	if err != nil {
-		return nil, err
+	var listener net.Listener
+	var err error
+
+	if hss.MuxListener != nil && strings.EqualFold(hss.Endpoint, hss.MuxListener.Addr().String()) {
+		listener = hss.MuxListener
+	} else {
+		if hss.MuxListener != nil {
+			err = hss.MuxListener.Close()
+			if err != nil {
+				return nil, err
+			}
+		}
+		listener, err = net.Listen("tcp", hss.Endpoint)
+		if err != nil {
+			return nil, err
+		}
 	}
 
 	if hss.TLSSetting != nil {