使用 nodejs pm2 扩展服务器时端口如何工作

Question

我正在学习如何在我设置的一个小沙箱中扩展服务器。这是非常简单的代码：

'use strict';

const express = require('express');
const bodyParser = require('body-parser');
const app = express();

const instanceId = parseInt(Math.random() * 1000);

//Allow all requests from all domains & localhost
app.all('/*', function(req, res, next) {
  res.header("Access-Control-Allow-Origin", "*");
  res.header("Access-Control-Allow-Headers", "X-Requested-With, Content-Type, Accept");
  res.header("Access-Control-Allow-Methods", "POST, GET");
  next();
});

app.use(bodyParser.json());
app.use(bodyParser.urlencoded({extended: false}));

app.get('/', function(req, res) {
  console.log(`[${new Date()}] ${req.method} ${req.originalUrl} from ${req.ip} at ${instanceId}`);
  res.send(`received at ${Date.now()} from ${instanceId}`);
});

app.listen(6069);

没什么特别的，只是吐出日期和收到请求的时间。

用于扩展 nodejs 服务器的 pm2 文档建议我运行:

pm2 start server.js -i 5

效果非常好。这是我使用 npm 模块负载测试对其进行压力测试时的示例输出：

server-0 [Sun Aug 07 2016 00:13:53 GMT-0400 (EDT)] GET / from ::ffff:127.0.0.1 at 847
server-1 [Sun Aug 07 2016 00:13:53 GMT-0400 (EDT)] GET / from ::ffff:127.0.0.1 at 261
server-3 [Sun Aug 07 2016 00:13:53 GMT-0400 (EDT)] GET / from ::ffff:127.0.0.1 at 328
server-2 [Sun Aug 07 2016 00:13:53 GMT-0400 (EDT)] GET / from ::ffff:127.0.0.1 at 163
server-4 [Sun Aug 07 2016 00:13:53 GMT-0400 (EDT)] GET / from ::ffff:127.0.0.1 at 351
server-0 [Sun Aug 07 2016 00:13:53 GMT-0400 (EDT)] GET / from ::ffff:127.0.0.1 at 847
server-3 [Sun Aug 07 2016 00:13:53 GMT-0400 (EDT)] GET / from ::ffff:127.0.0.1 at 328
server-1 [Sun Aug 07 2016 00:13:53 GMT-0400 (EDT)] GET / from ::ffff:127.0.0.1 at 261
server-2 [Sun Aug 07 2016 00:13:53 GMT-0400 (EDT)] GET / from ::ffff:127.0.0.1 at 163
server-4 [Sun Aug 07 2016 00:13:53 GMT-0400 (EDT)] GET / from ::ffff:127.0.0.1 at 351
server-0 [Sun Aug 07 2016 00:13:53 GMT-0400 (EDT)] GET / from ::ffff:127.0.0.1 at 847
server-3 [Sun Aug 07 2016 00:13:53 GMT-0400 (EDT)] GET / from ::ffff:127.0.0.1 at 328

这是我的问题。为什么节点没有抛出端口 6069 正在使用的错误？多个服务器正在尝试使用该端口——但没有任何抱怨。为什么？

Answer 1

PM2 创建了它自己的 "embedded load-balancer which uses Round-robin algorithm to better distribute load among the workers"。所以它基本上在您的应用程序周围包装了一个负载平衡器，并将请求代理到它创建的每个节点。

When using Round-robin scheduling policy, the master accepts() all incoming connections and sends the TCP handle for that particular connection to the chosen worker (via IPC).

使用 nodejs pm2 扩展服务器时端口如何工作

How ports work when scaling server using nodejs pm2

port

scalability

node.js

pm2

server