GoのGinでUnix Domain Socketを使う方法（Nginx経由）

GinでUnix Domain Socket

GinでUnix Domain Socketを使うには、net.Listen("unix", "/tmp/demo.sock")を使用します。

main.go

package main

import (
	"fmt"
	"net"
	"net/http"
	"runtime"

	"github.com/gin-gonic/gin"
)

func main() {
	router := gin.Default()

	router.GET("/ram", func(c *gin.Context) {
		var m runtime.MemStats
		runtime.ReadMemStats(&m)

		// Convert bytes to megabytes
		mb := m.Alloc / 1024 / 1024

		c.String(http.StatusOK, fmt.Sprintf("Current RAM usage: %v MB", mb))
	})

	listener, err := net.Listen("unix", "/tmp/demo.sock")
	if err != nil {
		panic(err)
	}

	http.Serve(listener, router)
}

Nginxの設定ファイル

$ brew install nginx

設定ファイルは、/opt/homebrew/etc/nginx/にあると思います。

demo.conf

upstream demo {
    server unix:/tmp/demo.sock;
}

# the nginx server instance
server {
    listen 8081;
    server_name localhost;

    location / {
      proxy_set_header X-Real-IP $remote_addr;
      proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
      proxy_set_header Host $http_host;
      proxy_set_header X-NginX-Proxy true;
      proxy_http_version 1.1; # for keep-alive
      proxy_pass http://demo/;
      proxy_redirect off;
    }
}

Graceful Shutdown版

GinでUnix Domain Socketを使用してGraceful Shutdownをするコードを示します。サーバー起動時の.sockファイルの削除（サーバークラッシュをケア）とサーバー停止時の.sockファイルの削除処理を追加しています。

router.SetTrustedProxies([]string{"127.0.0.1"})も大事なのでお忘れなく。

main.go

package main

import (
	"context"
	"errors"
	"fmt"
	"log"
	"net"
	"net/http"
	"os"
	"os/signal"
	"runtime"
	"syscall"
	"time"

	"github.com/gin-gonic/gin"
)

var socketPath = "/tmp/demo.sock"

func main() {
	// 1. Remove existing socket file if it exists from a previous crash
	if _, err := os.Stat(socketPath); err == nil {
		_ = os.Remove(socketPath)
	}

	router := gin.Default()

	// Trust NGINX proxy headers (highly recommended)
	router.SetTrustedProxies([]string{"127.0.0.1"})

	router.GET("/ram", func(c *gin.Context) {
		var m runtime.MemStats
		runtime.ReadMemStats(&m)

		// Convert bytes to megabytes
		mb := m.Alloc / 1024 / 1024

		c.String(http.StatusOK, fmt.Sprintf("Current RAM usage: %v MB", mb))
	})

	listener, err := net.Listen("unix", socketPath)
	if err != nil {
		panic(err)
	}

	server := &http.Server{
		Handler: router,
	}

	// 2. Run the server in a goroutine
	go func() {
		log.Printf("Starting Gin server on UNIX socket: %s", socketPath)

		if err := server.Serve(listener); err != nil && !errors.Is(err, http.ErrServerClosed) {
			log.Fatalf("Failed to run server: %v", err)
		}
	}()

	// 3. Fix permissions so NGINX can access the socket file
	// Give the socket file read/write permissions (adjust as needed for security)
	time.Sleep(100 * time.Millisecond) // Wait a brief moment for the file to be created
	if err := os.Chmod(socketPath, 0666); err != nil {
		log.Fatalf("Failed to set socket permissions: %v", err)
	}

	// 4. Graceful Shutdown handling to clean up the socket file
	quit := make(chan os.Signal, 1)
	signal.Notify(quit, syscall.SIGINT, syscall.SIGTERM)
	<-quit
	log.Println("Shutting down server...")

	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
	defer cancel()

	if err := server.Shutdown(ctx); err != nil {
		log.Fatal("Server forced to shutdown:", err)
	}

	// Always delete the socket file on exit
	_ = os.Remove(socketPath)
	log.Println("Server exiting, socket file removed.")
}

動作確認

Nginx側

demo.confをnginx-conf-directory/servers/demo.confに配置して、nginxを起動。

$ pbpaste > nginx-conf-directory/servers/demo.conf # macOSの場合
$ brew services reload nginx

Server側

$ mkdir workspace
$ cd workspace
$ go mod init example
$ go get github.com/gin-gonic/gin
$ pbpaste > main.go # macOSの場合
$ go run main.go

Client側

$ curl http://localhost:8081/ram 
Current RAM usage: 0 MB

参考

• Blazingly Fast Interprocess communication in Go using UNIX Sockets!!
• Googleで検索：🔍nginx unix domain socket to gin in golang