如何在其进程被杀死时如何正常关闭我的Express服务器？

Question

在生产中运行我的Express应用程序时,我希望在其进程被终止时(即发送SIGTERM或SIGINT)正常关闭服务器.

这是我的代码的简化版本:

const express = require('express');

const app = express();

app.get('/', (req, res) => res.json({ ping: true }));

const server = app.listen(3000, () => console.log('Running…'));

setInterval(() => server.getConnections(
    (err, connections) => console.log(`${connections} connections currently open`)
), 1000);

process.on('SIGTERM', shutDown);
process.on('SIGINT', shutDown);

function shutDown() {
    console.log('Received kill signal, shutting down gracefully');
    server.close(() => {
        console.log('Closed out remaining connections');
        process.exit(0);
    });

    setTimeout(() => {
        console.error('Could not close connections in time, forcefully shutting down');
        process.exit(1);
    }, 10000);
}

当我在浏览器中运行它并调用URL http:// localhost:3000 /时,setInterval函数中的日志语句将继续打印"1个当前打开的连接",直到我实际关闭浏览器窗口.即使关闭标签,显然也会保持连接打开.

所以,我按Ctrl + C杀了我的服务器,它将进入超时并在10秒后打印"无法关闭连接",同时继续打印"1个连接打开".

只有在我杀死进程之前关闭浏览器窗口时,才会收到"关闭剩余连接"消息.

我在这里错过了什么？正常关闭Express服务器的正确方法是什么？

Answer 1

如果有人有兴趣,我自己找到了解决方案(很想听到评论中的反馈).

我为服务器上的连接添加了一个监听器,在数组中存储对这些连接的引用.关闭连接后,它们将从阵列中删除.

当服务器被终止时,通过调用其end方法来关闭每个连接.对于某些浏览器(例如Chrome),这还不够,所以在超时后,我会调用destroy每个连接.

const express = require('express');

const app = express();

app.get('/', (req, res) => res.json({ ping: true }));

const server = app.listen(3000, () => console.log('Running…'));

setInterval(() => server.getConnections(
    (err, connections) => console.log(`${connections} connections currently open`)
), 1000);

process.on('SIGTERM', shutDown);
process.on('SIGINT', shutDown);

let connections = [];

server.on('connection', connection => {
    connections.push(connection);
    connection.on('close', () => connections = connections.filter(curr => curr !== connection));
});

function shutDown() {
    console.log('Received kill signal, shutting down gracefully');
    server.close(() => {
        console.log('Closed out remaining connections');
        process.exit(0);
    });

    setTimeout(() => {
        console.error('Could not close connections in time, forcefully shutting down');
        process.exit(1);
    }, 10000);

    connections.forEach(curr => curr.end());
    setTimeout(() => connections.forEach(curr => curr.destroy()), 5000);
}

Answer 2

您遇到的问题是所有现代浏览器都会为多个请求重复使用单个连接.这称为保持活动连接.

处理此问题的正确方法是监控所有新连接和请求,并跟踪每个连接的状态(现在是空闲还是活动).然后,您可以强制关闭所有空闲连接,并确保在处理当前请求后关闭活动连接.

我已经实现了@ moebius/http-graceful-shutdown模块,专门用于优雅地关闭整个Express应用程序和节点服务器.遗憾的是,也没有Express,也没有Node本身没有内置的功能.

以下是它如何与任何Express应用程序一起使用:

const express = require('express');
const GracefulShutdownManager = require('@moebius/http-graceful-shutdown').GracefulShutdownManager;


const app = express();

const server = app.listen(8080);

const shutdownManager = new GracefulShutdownManager(server);

process.on('SIGTERM', () => {
  shutdownManager.terminate(() => {
    console.log('Server is gracefully terminated');
  });
});

随意退房模块,GitHub页面有更多细节.

Answer 3

Express 的创建者推荐的开源项目https://github.com/godaddy/terminus ( https://expressjs.com/en/advanced/healthcheck-graceful-shutdown.html )。

终端使用的基本示例：

const http = require('http');
const express = require('express');
const terminus = require('@godaddy/terminus');

const app = express();

app.get('/', (req, res) => {
  res.send('ok');
});

const server = http.createServer(app);

function onSignal() {
  console.log('server is starting cleanup');
  // start cleanup of resource, like databases or file descriptors
}

async function onHealthCheck() {
  // checks if the system is healthy, like the db connection is live
  // resolves, if health, rejects if not
}

terminus(server, {
  signal: 'SIGINT',
   healthChecks: {
    '/healthcheck': onHealthCheck,
  },
  onSignal
});

server.listen(3000);

如果您需要服务器生命周期回调（即从服务注册表中注销实例等），terminus 有很多选项：

const options = {
  // healtcheck options
  healthChecks: {
    '/healthcheck': healthCheck    // a promise returning function indicating service health
  },

  // cleanup options
  timeout: 1000,                   // [optional = 1000] number of milliseconds before forcefull exiting
  signal,                          // [optional = 'SIGTERM'] what signal to listen for relative to shutdown
  signals,                          // [optional = []] array of signals to listen for relative to shutdown
  beforeShutdown,                  // [optional] called before the HTTP server starts its shutdown
  onSignal,                        // [optional] cleanup function, returning a promise (used to be onSigterm)
  onShutdown,                      // [optional] called right before exiting

  // both
  logger                           // [optional] logger function to be called with errors
};