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小沙箱中扩展服务器。这是非常简单的代码：

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\'use strict\';\n\nconst express = require(\'express\');\nconst bodyParser = require(\'body-parser\');\nconst app = express();\n\nconst instanceId = parseInt(Math.random() * 1000);\n\n//Allow all requests from all domains & localhost\napp.all(\'/*\', function(req, res, next) {\n  res.header("Access-Control-Allow-Origin", "*");\n  res.header("Access-Control-Allow-Headers", "X-Requested-With, Content-Type, Accept");\n  res.header("Access-Control-Allow-Methods", "POST, GET");\n  next();\n});\n\napp.use(bodyParser.json());\napp.use(bodyParser.urlencoded({extended: false}));\n\napp.get(\'/\', function(req, res) {\n  console.log(`[${new Date()}] ${req.method} ${req.originalUrl} from ${req.ip} at ${instanceId}`);\n  res.send(`received at ${Date.now()} from ${instanceId}`);\n});\n\napp.listen(6069);\n

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没什么疯狂的，只是吐出日期和收到请求的实例。

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用于扩展 Nodejs 服务器的 pm2 文档建议我运行：

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pm2 start server.js -i 5\n

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效果非常好。这是我使用 npm 模块 loadtest 对其进行压力测试时的示例输出：

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

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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端口\xe2\x80\x94，但没有抱怨。为什么？

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Answer 1

PM2 创建了自己的“嵌入式负载均衡器，它使用循环算法来更好地在工作人员之间分配负载”。因此，它基本上在您的应用程序周围包装了一个负载均衡器，并将请求代理到它创建的每个节点。

当使用循环调度策略时，主节点accept()所有传入连接并将该特定连接的TCP句柄发送给所选的工作节点（通过IPC）。