基本介绍

​gproc​组件提供了统一的信号监听和回调处理功能，目的是解决在程序中多个不同组件冗余的信号处理逻辑，以及接收退出信号后无法平滑析构的痛点。在没有统一退出信号监听的组件下，当多个组件通过​goroutine​异步监听信号，主​goroutine​接收到退出信号往往会直接退出，或者等待一段无法预测的时间退出，造成程序其实无法平滑退出，可能引起一些不可预料的问题。​gproc​通过统一的信号注册和回调处理，使得各个组件能够有效地接收到退出信号并做相应析构处理，使得程序的信号处理逻辑更加严谨。

相关方法：

// AddSigHandler adds custom signal handler for custom one or more signals.
func AddSigHandler(handler SigHandler, signals ...os.Signal)

// AddSigHandlerShutdown adds custom signal handler for shutdown signals:
// syscall.SIGINT,
// syscall.SIGQUIT,
// syscall.SIGKILL,
// syscall.SIGTERM,
// syscall.SIGABRT.
func AddSigHandlerShutdown(handler ...SigHandler)

// Listen blocks and does signal listening and handling.
func Listen()

简要介绍：

• ​AddSigHanlder​方法用于添加对指定信号的监听和对应回调函数注册。
• ​AddSigHandlerShutdown​方法用于添加对常见进程退出信号的监听和对应回调函数注册。
• ​Listen​方法用于阻塞监听信号并自动执行回调函数调用。

我们来看两个示例。

示例1，使用标准库信号监听

package main

import (
	"fmt"
	"os"
	"os/signal"
	"syscall"
	"time"
)

func signalHandlerForMQ() {
	var (
		sig          os.Signal
		receivedChan = make(chan os.Signal)
	)
	signal.Notify(
		receivedChan,
		syscall.SIGINT,
		syscall.SIGQUIT,
		syscall.SIGKILL,
		syscall.SIGTERM,
		syscall.SIGABRT,
	)
	for {
		sig = <-receivedChan
		fmt.Println("MQ is shutting down due to signal:", sig.String())
		time.Sleep(time.Second)
		fmt.Println("MQ is shut down smoothly")
		return
	}
}

func main() {
	fmt.Println("Process start, pid:", os.Getpid())
	go signalHandlerForMQ()

	var (
		sig          os.Signal
		receivedChan = make(chan os.Signal)
	)
	signal.Notify(
		receivedChan,
		syscall.SIGINT,
		syscall.SIGQUIT,
		syscall.SIGKILL,
		syscall.SIGTERM,
		syscall.SIGABRT,
	)
	for {
		sig = <-receivedChan
		fmt.Println("MainProcess is shutting down due to signal:", sig.String())
		return
	}
}

我们通过​go run​命令来执行一下，随后通过​Ctrl+C​快捷键退出（Mac用户通过​Command+C​）。

$ go run signal_handler.go
Process start, pid: 21928
^CMainProcess is shutting down due to signal: interrupt
MQ is shutting down due to signal: interrupt

可以看到，好可惜，那个​MQ​的​goroutine​还没完全退出进程即被强行关闭。

示例2，使用gproc信号监听

package main

import (
	"fmt"
	"github.com/gogf/gf/v2/os/gproc"
	"os"
	"time"
)

func signalHandlerForMQ(sig os.Signal) {
	fmt.Println("MQ is shutting down due to signal:", sig.String())
	time.Sleep(time.Second)
	fmt.Println("MQ is shut down smoothly")
}

func signalHandlerForMain(sig os.Signal) {
	fmt.Println("MainProcess is shutting down due to signal:", sig.String())
}

func main() {
	fmt.Println("Process start, pid:", os.Getpid())
	gproc.AddSigHandlerShutdown(
		signalHandlerForMQ,
		signalHandlerForMain,
	)
	gproc.Listen()
}

我们通过​go run​命令来执行一下，随后通过​Ctrl+C​快捷键退出（Mac用户通过​Command+C​）。

$ go run signal_handler_gproc.go
Process start, pid: 22876
^CMQ is shutting down due to signal: interrupt
MainProcess is shutting down due to signal: interrupt
MQ is shut down smoothly

看到差别了吧，所有的信号监听函数都正常结束后，随后进程退出。