go-优雅地重启http服务之endless

不停服地重启http服务.

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前篇

• endless 仓库: https://github.com/fvbock/endless
  • 示例: https://github.com/fvbock/endless/tree/master/examples
• gin 仓库 (start 好高) : https://github.com/gin-gonic/gin
• 如何优雅地重启go程序–endless篇 (有源码分析) - https://blog.csdn.net/tomatomas/article/details/94839857
• Golang优雅重启HTTP服务 - https://segmentfault.com/a/1190000013757098
• 平滑重启 - https://www.cnblogs.com/CraryPrimitiveMan/p/8560839.html

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目的

• 不关闭现有连接（正在运行中的程序）
• 新的进程启动并替代旧进程
• 新的进程接管新的连接
• 连接要随时响应用户的请求，当用户仍在请求旧进程时要保持连接，新用户应请求新进程，不可以出现拒绝请求的情况

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流程

1. 替换可执行文件或修改配置文件

2. 发送信号量 SIGHUP

3. 拒绝新连接请求旧进程，但要保证已有连接正常

4. 启动新的子进程

5. 新的子进程开始 Accet

6. 系统将新的请求转交新的子进程

7. 旧进程处理完所有旧连接后正常结束

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使用

测试代码

• endless.go

  package main
  
  import (
  	"fmt"
  	"github.com/gin-gonic/gin"
  	"log"
  	"net/http"
  	"strconv"
  	"syscall"
  	"time"
  
  	"github.com/fvbock/endless"
  )
  
  func main() {
  	// gin
  	router := gin.Default()
  	router.GET("/hello", func(c *gin.Context) {
  		delay := c.Query("delay")
  		dt, _ := strconv.Atoi(delay)
  		log.Printf("--- sleep time: %d", dt)
  		time.Sleep(time.Second * time.Duration(dt))
  		c.String(http.StatusOK, "world 111") // 返回值
  	})
  
  	// endless
  	endless.DefaultReadTimeOut = 10 * time.Second
  	endless.DefaultWriteTimeOut = 30 * time.Second // 写 超时时间为 30s
  	endless.DefaultMaxHeaderBytes = 1 << 20        // 请求头最大为 1m
  	endPoint := fmt.Sprintf(":%d", 8811)           // 端口
  
  	srv := endless.NewServer(endPoint, router)
  	srv.BeforeBegin = func(add string) {
  		log.Printf("Actual pid is %d", syscall.Getpid())
  	}
  
  	err := srv.ListenAndServe()
  	if err != nil {
  		log.Printf("Server err: %v", err)
  	}
  }

测试流程:

1. 编译 并 启动服务

   $ go build endless.go
   $ ./endless >> out.file 2>&1
   [1] 8723 # endless 的进程

2. 请求1: curl 请求一下, 延时 20s 才返回 (不能超过定义的 30s)

   $ curl http://192.168.1.200:8811/hello?delay=20
   world 111 # 20 秒后返回的结果

3. 修改 endless.go 返回值

   $ vim endless.go
   
   c.String(http.StatusOK, "world 222")

   重新编译

   $ go build endless.go

4. kill 掉就 endless (8723) 进程, 也就发送一个 SIGHUP 信号

   $ kill -1 8723

5. 请求2: curl 请求一下, 延时 10s 才返回

   $ curl http://192.168.1.200:8811/hello?delay=10
   world 222 # 10 秒后返回的结果

测试日志

• out.file 日志

  root@NAS-Wilker:~/go-workspace/src/ftp-golab/test_net/test_http/endless# tail -f out.file 
  
  # 步骤 1
  [GIN-debug] [WARNING] Creating an Engine instance with the Logger and Recovery middleware already attached.
  
  [GIN-debug] [WARNING] Running in "debug" mode. Switch to "release" mode in production.
   - using env:	export GIN_MODE=release
   - using code:	gin.SetMode(gin.ReleaseMode)
  
  [GIN-debug] GET    /hello                    --> main.main.func1 (3 handlers)
  2021/01/16 21:54:53 Actual pid is 8723 # 进程号
  
  # 步骤 2
  2021/01/16 21:55:22 --- sleep time: 20
  
  # 步骤 4
  2021/01/16 21:55:34 8723 Received SIGHUP. forking.
  [GIN-debug] [WARNING] Creating an Engine instance with the Logger and Recovery middleware already attached.
  
  [GIN-debug] [WARNING] Running in "debug" mode. Switch to "release" mode in production.
   - using env:	export GIN_MODE=release
   - using code:	gin.SetMode(gin.ReleaseMode)
  
  [GIN-debug] GET    /hello                    --> main.main.func1 (3 handlers)
  2021/01/16 21:55:34 8723 Received SIGTERM.
  2021/01/16 21:55:34 8723 Waiting for connections to finish...
  2021/01/16 21:55:34 8723 [::]:8811 Listener closed.
  2021/01/16 21:55:34 Actual pid is 8801 # 新的进程号
  
  # 步骤 5
  2021/01/16 21:55:36 --- sleep time: 10
  [GIN] 2021/01/16 - 21:55:42 | 200 | 20.000313266s |     192.168.2.2 | GET      /hello?delay=20 # 旧进程返回
  2021/01/16 21:55:42 8723 Serve() returning...
  2021/01/16 21:55:42 Server err: accept tcp [::]:8811: use of closed network connection
  [GIN] 2021/01/16 - 21:55:46 | 200 | 10.000305757s |     192.168.2.2 | GET      /hello?delay=10 # 新进程返回

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分析

信号的监听

func (srv *endlessServer) handleSignals() {
	 	// 几个关键的信号
		case syscall.SIGHUP: // 1, fork 子进程
			log.Println(pid, "Received SIGHUP. forking.")
			err := srv.fork()
			if err != nil {
				log.Println("Fork err:", err)
			}
		case syscall.SIGINT: // 2, 也就是 ctrl + c
			log.Println(pid, "Received SIGINT.")
			srv.shutdown()
		case syscall.SIGTERM: // 15, 也就是 kill 默认信号
			log.Println(pid, "Received SIGTERM.")
			srv.shutdown()
}

fork 运行子进程

所以重新编译成程序名必须和一开始使用的程序名一致, 准确的说 fork 时使用了最开始运行命令的所有参数, 必须完全一致.

func (srv *endlessServer) fork() (err error) {
	// 
	// log.Println(files)
	path := os.Args[0]
	var args []string
	if len(os.Args) > 1 {
		args = os.Args[1:]
	}

	cmd := exec.Command(path, args...)
	return
}

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