如何在父进程的 SIGINT 上永久监控子进程？

Question

我在 Windows 上使用forever-monitor，默认情况下child processes are detached。

在我的应用程序中，我有一个 monitor.js 文件，它监视一个 server.js 文件，我希望能够在我通过退出 monitor.js 关闭我的应用程序时通知 server.js（在命令上点击 Ctrl + C -行）。

这是我的演示代码：

monitor.js

const path = require('path');
const forever = require('forever-monitor');

let child;

function exit() {
  console.error('Received exit signal on main process.');
  if (child) {
    // TODO: Here I want to notify the "child", so that it can gracefully shutdown my server
    child.stop();
  }
  process.exit(0);
}

['SIGINT', 'SIGKILL', 'SIGTERM'].forEach(signal => process.on(signal, exit));

child = new forever.Monitor(path.join(__dirname, 'server.js'));
child.start();

server.js

const express = require('express');

const app = express();
const port = process.env.PORT || 8080;

let server;

function stopServer() {
  if (server) {
    console.log('Shutting down server...');
    server.close();
  }
}

app.get('/', (request, response) => response.send('Hello'));
server = app.listen(port, () => console.log(`Server is running on port "${port}".`));

当monitor.js 收到SIGINT 时，我如何在server.js 中调用stopServer？

Answer 1

秘诀是使用“fork”选项启动子进程。

使用“fork”选项可以通过调用child.send 将消息从父进程发送到子进程。这提供了在子进程中侦听来自父进程的自定义close 消息的能力，以便子进程可以停止服务器并使用自定义退出代码1337 退出。

当父/主进程意识到子进程已用代码1337 关闭时，主进程也会关闭。

这是我的解决方案：

monitor.js

const path = require('path');
const forever = require('forever-monitor');

let child;

function exit(signal) {
  console.error(`Received "${signal}" signal on main process.`);
  if (child) {
    child.send({action: 'close'});
  }
}

['SIGINT', 'SIGKILL', 'SIGTERM'].forEach(signal => process.on(signal, () => exit(signal)));

process.on('exit', (code) => console.log(`Stopped main process with code "${code}".`));

const options = {fork: true};

child = new forever.Monitor(path.join(__dirname, 'server.js'), options);

child.on('exit:code', (code) => {
  if (code === 1337) {
    if (child) {
      child.stop();
      console.log('Successfully stopped child process.');
    }
    console.log('Stopping main process ...');
    process.exit(0);
  }
});

child.start();

server.js

const express = require('express');

const app = express();
const port = process.env.PORT || 8080;

let server;

if (process.send) {
  process.on('message', function (message) {
    console.log(`Received "${message.action}" message from main process.`);
    if (message.action === 'close') {
      stopServer();
    }
  });
}

function stopServer() {
  if (server) {
    console.log('Stopping server in child process ...');
    server.close(() => {
      console.log('Stopped server in child process.');
      process.exit(1337);
    });
  }
}

app.get('/', (request, response) => response.send('Hello'));
server = app.listen(port, () => console.log(`Server is running on port "${port}".`));