如何在父进程中从SIGINT上的永久监视器通知子进程?

Question

我在Windows上使用永久监视器，默认情况下子进程是分离的。

在我的应用程序中，我有一个监视server.js文件的monitor.js文件，我希望能够在通过退出monitor.js(在命令行上按Ctrl + C(关闭应用程序时通知server.js。

这是我的演示代码：

监视器.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();

服务器.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，如何拨打server.jsstopServer？

Answer 1

秘诀是使用选项"fork"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退出1337。

当父进程/主进程意识到子进程已被代码1337关闭时，主进程也会关闭。

这是我的解决方案：

监视器.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();

服务器.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}".`));