Allow SO_REUSEPORT

BUILD

@@ -1,5 +1,5 @@
-load("@rules_go//go:def.bzl", "go_binary", "go_library")
 load("@gazelle//:def.bzl", "gazelle")
+load("@rules_go//go:def.bzl", "go_binary", "go_library")
 
 gazelle(name = "gazelle")
 
@@ -11,6 +11,9 @@ go_library(
     ],
     importpath = "aws-in-a-box",
     visibility = ["//visibility:private"],
+    x_defs = {
+        "aws-in-a-box.BazelSuffix": " (Bazel)",
+    },
     deps = [
         "//arn",
         "//http",
@@ -20,10 +23,8 @@ go_library(
         "//services/kms",
         "//services/s3",
         "//services/sqs",
+        "@org_golang_x_sys//unix",
     ],
-    x_defs = {
-        "aws-in-a-box.BazelSuffix": " (Bazel)"
-    },
 )
 
 go_binary(

MODULE.bazel

@@ -23,4 +23,5 @@ use_repo(
     "com_github_google_go_cmp",
     "org_golang_x_exp",
     "org_golang_x_net",
+    "org_golang_x_sys",
 )

go.mod

@@ -29,5 +29,6 @@ require (
 	github.com/aws/aws-sdk-go-v2/service/internal/s3shared v1.17.3 // indirect
 	github.com/jmespath/go-jmespath v0.4.0 // indirect
 	github.com/x448/float16 v0.8.4 // indirect
+	golang.org/x/sys v0.18.0
 	golang.org/x/text v0.14.0 // indirect
 )

go.sum

@@ -51,6 +51,8 @@ golang.org/x/exp v0.0.0-20230905200255-921286631fa9 h1:GoHiUyI/Tp2nVkLI2mCxVkOjs
 golang.org/x/exp v0.0.0-20230905200255-921286631fa9/go.mod h1:S2oDrQGGwySpoQPVqRShND87VCbxmc6bL1Yd2oYrm6k=
 golang.org/x/net v0.22.0 h1:9sGLhx7iRIHEiX0oAJ3MRZMUCElJgy7Br1nO+AMN3Tc=
 golang.org/x/net v0.22.0/go.mod h1:JKghWKKOSdJwpW2GEx0Ja7fmaKnMsbu+MWVZTokSYmg=
+golang.org/x/sys v0.18.0 h1:DBdB3niSjOA/O0blCZBqDefyWNYveAYMNF1Wum0DYQ4=
+golang.org/x/sys v0.18.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
 golang.org/x/text v0.14.0 h1:ScX5w1eTa3QqT8oi6+ziP7dTV1S2+ALU0bI+0zXKWiQ=
 golang.org/x/text v0.14.0/go.mod h1:18ZOQIKpY8NJVqYksKHtTdi31H5itFRjB5/qKTNYzSU=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=

main.go

@@ -1,14 +1,19 @@
 package main
 
 import (
+	"context"
 	"flag"
 	"log"
 	"log/slog"
+	"net"
 	"os"
 	"runtime/debug"
 	"strings"
+	"syscall"
 	"time"
 
+	"golang.org/x/sys/unix"
+
 	"aws-in-a-box/arn"
 	"aws-in-a-box/http"
 	"aws-in-a-box/server"
@@ -42,6 +47,7 @@ func versionString() string {
 
 func main() {
 	addr := flag.String("addr", "localhost:4569", "Address to run on")
+	reusePort := flag.Bool("reuse-port", false, "If true, sets the SO_REUSEPORT socket option")
 	persistDir := flag.String("persistDir", "", "Directory to persist data to. If empty, data is not persisted.")
 	logLevel := flag.String("logLevel", "debug", "debug/info/warn/error")
 
@@ -172,9 +178,30 @@ func main() {
 	}
 
 	srv := server.NewWithHandlerChain(handlerChain...)
-	srv.Addr = *addr
 
-	err := srv.ListenAndServe()
+	lc := net.ListenConfig{
+		Control: func(network, address string, conn syscall.RawConn) error {
+			if !*reusePort {
+				return nil
+			}
+
+			var setSockoptErr error
+			err := conn.Control(func(fd uintptr) {
+				setSockoptErr = syscall.SetsockoptInt(int(fd), syscall.SOL_SOCKET, unix.SO_REUSEPORT, 1)
+			})
+			if err != nil {
+				return err
+			}
+			return setSockoptErr
+		},
+	}
+
+	l, err := lc.Listen(context.Background(), "tcp", *addr)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	err = srv.Serve(l)
 	if err != nil {
 		panic(err)
 	}

services/s3/BUILD.bazel

@@ -14,5 +14,6 @@ go_library(
         "//atomicfile",
         "//awserrors",
         "@com_github_gofrs_uuid_v5//:uuid",
+        "@org_golang_x_exp//maps",
     ],
 )