Add ReusePort config to confighttp

.chloggen/so-reuse-port.yaml

@@ -0,0 +1,25 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: enhancement
+
+# The name of the component, or a single word describing the area of concern, (e.g. otlpreceiver)
+component: pkg/config/confignet
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Added ReusePort option to confignet.AddrConfig to enable SO_REUSEPORT on supported platforms.
+
+# One or more tracking issues or pull requests related to the change
+issues: [14046]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext:
+
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: []

.github/workflows/utils/cspell.json

@@ -72,6 +72,7 @@
       "RCPC",
       "Rahul",
       "SASL",
+      "SO_REUSEPORT",
       "Samplingdecision",
       "Sharma",
       "Statefulness",

config/confignet/README.md

@@ -13,6 +13,7 @@ leverage network configuration to set connection and transport information.
 - `transport`: Known protocols are "tcp", "tcp4" (IPv4-only), "tcp6"
   (IPv6-only), "udp", "udp4" (IPv4-only), "udp6" (IPv6-only), "ip", "ip4"
   (IPv4-only), "ip6" (IPv6-only), "unix", "unixgram" and "unixpacket".
+- `reuse_port`: If set to `true`, enables the SO_REUSEPORT socket option on the listener, allowing multiple processes to listen on the same port
 - `dialer`: Dialer configuration
   - `timeout`: Dialer timeout is the maximum amount of time a dial will wait for a connect to complete. The default is no timeout.
 

config/confignet/confignet.go

@@ -84,6 +84,13 @@ type AddrConfig struct {
 
 	// DialerConfig contains options for connecting to an address.
 	DialerConfig DialerConfig `mapstructure:"dialer,omitempty"`
+
+	// ReusePort enables the SO_REUSEPORT socket option on the listener.
+	// This allows multiple server instances to bind to the same address/port.
+	// This is useful for horizontal scaling and zero-downtime restarts.
+	// Note: This option is only supported on Linux and Darwin-based operating systems.
+	ReusePort bool `mapstructure:"reuse_port,omitempty"`
+
 	// prevent unkeyed literal initialization
 	_ struct{}
 }
@@ -103,11 +110,19 @@ func (na *AddrConfig) Dial(ctx context.Context) (net.Conn, error) {
 
 // Listen equivalent with net.ListenConfig's Listen for this address.
 func (na *AddrConfig) Listen(ctx context.Context) (net.Listener, error) {
-	lc := net.ListenConfig{}
+	lc, err := na.getListenConfig()
+	if err != nil {
+		return nil, err
+	}
 	return lc.Listen(ctx, string(na.Transport), na.Endpoint)
 }
 
 func (na *AddrConfig) Validate() error {
+	_, err := na.getListenConfig()
+	if err != nil {
+		return err
+	}
+
 	switch na.Transport {
 	case TransportTypeTCP,
 		TransportTypeTCP4,

config/confignet/confignet_test.go

@@ -7,6 +7,7 @@ import (
 	"context"
 	"errors"
 	"net"
+	"runtime"
 	"testing"
 	"time"
 
@@ -159,3 +160,73 @@ func Test_TransportType_UnmarshalText(t *testing.T) {
 	err = tt.UnmarshalText([]byte("invalid"))
 	require.Error(t, err)
 }
+
+func TestServerReusePort(t *testing.T) {
+	if runtime.GOOS != "linux" && runtime.GOOS != "darwin" {
+		sc := &AddrConfig{
+			Endpoint:  "localhost:4318",
+			Transport: TransportTypeTCP,
+			ReusePort: true,
+		}
+
+		_, err := sc.Listen(t.Context())
+		require.EqualError(t, err, "ReusePort is not supported on this platform")
+		return
+	}
+
+	tests := []struct {
+		name          string
+		reusePort     bool
+		expectedError bool
+	}{
+		{
+			name:          "ReusePort enabled",
+			reusePort:     true,
+			expectedError: false,
+		},
+		{
+			name:          "ReusePort disabled",
+			reusePort:     false,
+			expectedError: true,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			sc := &AddrConfig{
+				Endpoint:  "localhost:4318",
+				Transport: TransportTypeTCP,
+				ReusePort: tt.reusePort,
+			}
+
+			ln1, err := sc.Listen(t.Context())
+			require.NoError(t, err)
+			defer ln1.Close()
+
+			ln2, err := sc.Listen(t.Context())
+			if tt.expectedError {
+				require.Error(t, err)
+			} else {
+				require.NoError(t, err)
+			}
+
+			if ln2 != nil {
+				ln2.Close()
+			}
+		})
+	}
+}
+
+func TestServerConfigValidate(t *testing.T) {
+	sc := &AddrConfig{
+		Endpoint:  "localhost:4318",
+		Transport: TransportTypeTCP,
+		ReusePort: true,
+	}
+
+	if runtime.GOOS != "linux" && runtime.GOOS != "darwin" {
+		require.Error(t, sc.Validate())
+	} else {
+		require.NoError(t, sc.Validate())
+	}
+}

config/confignet/go.mod

@@ -5,6 +5,7 @@ go 1.25.0
 require (
 	github.com/stretchr/testify v1.11.1
 	go.uber.org/goleak v1.3.0
+	golang.org/x/sys v0.39.0
 )
 
 require (

config/confignet/listen_config_other.go

@@ -0,0 +1,18 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+//go:build !(linux || darwin)
+
+package confignet // import "go.opentelemetry.io/collector/config/confignet"
+
+import (
+	"errors"
+	"net"
+)
+
+func (na *AddrConfig) getListenConfig() (net.ListenConfig, error) {
+	if na.ReusePort {
+		return net.ListenConfig{}, errors.New("ReusePort is not supported on this platform")
+	}
+
+	return net.ListenConfig{}, nil
+}

config/confignet/listen_config_unix.go

@@ -0,0 +1,30 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+//go:build linux || darwin
+
+package confignet // import "go.opentelemetry.io/collector/config/confignet"
+
+import (
+	"net"
+	"syscall"
+
+	"golang.org/x/sys/unix"
+)
+
+func (na *AddrConfig) getListenConfig() (net.ListenConfig, error) {
+	cfg := net.ListenConfig{}
+	if na.ReusePort {
+		cfg.Control = func(_, _ string, c syscall.RawConn) error {
+			var controlErr error
+			err := c.Control(func(fd uintptr) {
+				controlErr = unix.SetsockoptInt(int(fd), unix.SOL_SOCKET, unix.SO_REUSEPORT, 1)
+			})
+			if err != nil {
+				return err
+			}
+			return controlErr
+		}
+	}
+
+	return cfg, nil
+}