本文介绍了Node.Js中实现端口重用原理详解,分享给大家,具体如下:
起源,从官方实例中看多进程共用端口
const cluster = require('cluster'); const http = require('http'); const numCPUs = require('os').cpus().length; if (cluster.isMaster) { console.log(`Master ${process.pid} is running`); for (let i = 0; i < numCPUs; i++) { cluster.fork(); } cluster.on('exit', (worker, code, signal) => { console.log(`worker ${worker.process.pid} died`); }); } else { http.createServer((req, res) => { res.writeHead(200); res.end('hello world\n'); }).listen(8000); console.log(`Worker ${process.pid} started`); }
执行结果:
$ node server.js
Master 3596 is running
Worker 4324 started
Worker 4520 started
Worker 6056 started
Worker 5644 started
了解http.js模块:
我们都只有要创建一个http服务,必须引用http模块,http模块最终会调用net.js实现网络服务
// lib/net.js 'use strict'; ... Server.prototype.listen = function(...args) { ... if (options instanceof TCP) { this._handle = options; this[async_id_symbol] = this._handle.getAsyncId(); listenInCluster(this, null, -1, -1, backlogFromArgs); // 注意这个方法调用了cluster模式下的处理办法 return this; } ... }; function listenInCluster(server, address, port, addressType,backlog, fd, exclusive) { // 如果是master 进程或者没有开启cluster模式直接启动listen if (cluster.isMaster || exclusive) { //_listen2,细心的人一定会发现为什么是listen2而不直接使用listen // _listen2 包裹了listen方法,如果是Worker进程,会调用被hack后的listen方法,从而避免出错端口被占用的错误 server._listen2(address, port, addressType, backlog, fd); return; } const serverQuery = { address: address, port: port, addressType: addressType, fd: fd, flags: 0 }; // 是fork 出来的进程,获取master上的handel,并且监听, // 现在是不是很好奇_getServer方法做了什么 cluster._getServer(server, serverQuery, listenOnMasterHandle); } ...
答案很快就可以通过cluster._getServer 这个函数找到
// lib/internal/cluster/child.js cluster._getServer = function(obj, options, cb) { // ... const message = util._extend({ act: 'queryServer', // 关键点:构建一个queryServer的消息 index: indexes[indexesKey], data: null }, options); message.address = address; // 发送queryServer消息给master进程,master 在收到这个消息后,会创建一个开始一个server,并且listen send(message, (reply, handle) => { rr(reply, indexesKey, cb); // Round-robin. }); obj.once('listening', () => { cluster.worker.state = 'listening'; const address = obj.address(); message.act = 'listening'; message.port = address && address.port || options.port; send(message); }); }; //... // Round-robin. Master distributes handles across workers. function rr(message, indexesKey, cb) { if (message.errno) return cb(message.errno, null); var key = message.key; // 这里hack 了listen方法 // 子进程调用的listen方法,就是这个,直接返回0,所以不会报端口被占用的错误 function listen(backlog) { return 0; } // ... const handle = { close, listen, ref: noop, unref: noop }; handles[key] = handle; // 这个cb 函数是net.js 中的listenOnMasterHandle 方法 cb(0, handle); } // lib/net.js /* function listenOnMasterHandle(err, handle) { err = checkBindError(err, port, handle); server._handle = handle; // _listen2 函数中,调用的handle.listen方法,也就是上面被hack的listen server._listen2(address, port, addressType, backlog, fd); } */
master进程收到queryServer消息后进行启动服务
// lib/internal/cluster/master.js function queryServer(worker, message) { const args = [ message.address, message.port, message.addressType, message.fd, message.index ]; const key = args.join(':'); var handle = handles[key]; // 如果地址没被监听过,通过RoundRobinHandle监听开启服务 if (handle === undefined) { var constructor = RoundRobinHandle; if (schedulingPolicy !== SCHED_RR || message.addressType === 'udp4' || message.addressType === 'udp6') { constructor = SharedHandle; } handles[key] = handle = new constructor(key, address, message.port, message.addressType, message.fd, message.flags); } // 如果地址已经被监听,直接绑定handel到已经监听到服务上,去消费请求 // Set custom server data handle.add(worker, (errno, reply, handle) => { reply = util._extend({ errno: errno, key: key, ack: message.seq, data: handles[key].data }, reply); if (errno) delete handles[key]; // Gives other workers a chance to retry. send(worker, reply, handle); }); }
看到这一步,已经很明显,我们知道了多进行端口共享的实现原理
那现在问题来了,既然Worker进程是如何获取到master进程监听服务接收到的connect呢?
// lib/internal/cluster/round_robin_handle.js function RoundRobinHandle(key, address, port, addressType, fd) { this.server = net.createServer(assert.fail); if (fd >= 0) this.server.listen({ fd }); else if (port >= 0) this.server.listen(port, address); else this.server.listen(address); // UNIX socket path. this.server.once('listening', () => { this.handle = this.server._handle; // 监听onconnection方法 this.handle.onconnection = (err, handle) => this.distribute(err, handle); this.server._handle = null; this.server = null; }); } RoundRobinHandle.prototype.add = function (worker, send) { // ... }; RoundRobinHandle.prototype.remove = function (worker) { // ... }; RoundRobinHandle.prototype.distribute = function (err, handle) { // 负载均衡地挑选出一个worker this.handles.push(handle); const worker = this.free.shift(); if (worker) this.handoff(worker); }; RoundRobinHandle.prototype.handoff = function (worker) { const handle = this.handles.shift(); const message = { act: 'newconn', key: this.key }; // 向work进程其发送newconn内部消息和客户端的句柄handle sendHelper(worker.process, message, handle, (reply) => { // ... this.handoff(worker); }); };
下面让我们看看Worker进程接收到newconn消息后进行了哪些操作
// lib/child.js function onmessage(message, handle) { if (message.act === 'newconn') onconnection(message, handle); else if (message.act === 'disconnect') _disconnect.call(worker, true); } // Round-robin connection. // 接收连接,并且处理 function onconnection(message, handle) { const key = message.key; const server = handles[key]; const accepted = server !== undefined; send({ ack: message.seq, accepted }); if (accepted) server.onconnection(0, handle); }
总结
分享出于共享学习的目的,如有错误,欢迎大家留言指导,不喜勿喷。也希望大家多多支持。