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This article shows you how to use cluster to achieve multi-process in nodejs, concise and easy to understand, absolutely can make your eyes shine, through the detailed introduction of this article I hope you can gain something.

cluster

node module for multi-process;

properties and methods

isMaster property, returns whether it is the main process, boolean value;

isWorker property, returns whether the process is a worker process;

fork() method, which can only be called by the main process to spawn a new worker child process and return the worker object;

setupMaster([setting]) method, used to modify the default behavior of fork, once called, will be set according to cluster.settings.

settings Properties; used for configuration;

parameter exec:worker file path,

args: parameters passed to worker;

execArgv: a list of parameters passed to the nodejs executable;

const cluster = require('cluster');const cpuNums = require('os').cpus().length;const http = require('http');if (cluster.isMaster) { console.log(cpuNums); for (var i = 0; i

< cpuNums; i++) { cluster.fork(); // 相当于node main.js，重新执行自己 // 和process_child相比，不用重新创建child.js， } cluster.on('fork', worker =>

{ console.log(`主进程fork了一个worker，pid为${worker.process.pid}`) }) cluster.on('listening', worker => { console.log(`主进程fork了一个worker，pid为${worker.process.pid}`) }) cluster.on('message', data => { console.log('主进程接收到了子进程消息为：'，data) }) Object.keys(cluster.workers).forEach(item => { cluster.workers[item].on('message', data => { console.log(data); }); }); cluster.on('disconnect', (worker) => { console.log('有工作进程退出了'，worker.process.pid) })} else { http.createServer((req, res) => { res.end('hello') }).listen(8001, () =>{ console.log('child server is runing') }) console.log('我是子进程'); process.send('子说：你好');}事件

fork事件，当新的工作进程被fork时触发，可以用来记录工作进程活动;

listening事件，当一个工作进程调用listen()后触发，事件处理器两个参数：worker:工作进程对象, address:包含了链接属性

只有http的服务的listen事件才能触发此事件

message事件，监听子进程的消息;当cluster主进程接收任何工作进程发送的消息时触发;

比较特殊需要在单独的worker上监听;

online事件，

disconnect事件，当工作进程断开时调用;

exit事件，

setup事件，cluster.setupMaster()执行后触发;

cluster多进程模型

每个worker进程通过使用cluster.fork()函数，基于IPC(Inter-Process-Communication),实现与master进程间通信;

那通过child_process.fork()直接创建不就可以了，为什么要通过cluster

这种方式只实现了多进程，多进程运行还涉及父子进程通信，子进程管理，以及负载均衡等问题，这些特性cluster已经做了处理了;

惊群现象

多个进程间会竞争一个accept连接，产生惊群现象，效率比较低;

由于无法控制一个新的连接由哪个进程来处理，导致worker进程间负载不均衡;

master.js

const net = require('net'); // 是最基础的网络模块，http的基础就是网络模块，最底层是socketconst fork = require('child_process').fork; // 惊群var handle = net._createServerHandle('0.0.0.0', 5000); // net模块创建一个服务，绑定到3000端口，返回一个callbackfor (var i = 0; i

< 4; i++) { console.log('fork', i); fork('./worket.js').send({}, handle); // 主进程fork子进程，send信息} worker.js const net = require('net');process.on('message', (m, handle) =>

{ //child process receives master message// master receives client request, worker responds to start(handle);});var buf = 'hello nodejs';var res =<$'HTTP/1.1 200 OK','content-length' + buf.length].join ('\r\n')+ ' \r\n' + buf;var data = {}; function start(server) { //Response logic, Focus on crowd effect, Count server.listen(); server.onconnection = function(err, hand) { var pid = process.pid; if (! data[pid]) { data[pid] = 0; } data[pid]++; console.log('get a connection on worker,pid = %d', process.pid, data[pid]); var socket = net.Socket({ handle: hand }); socket.readable = socket.writable = true; //modify socket read-write properties socket.end(res); };}nginx proxy

Nginx is a very lightweight http server written by Russians. It is a high-performance HTTP and reverse proxy server, asynchronous non-blocking I/O, and capable of high concurrency.

Forward proxy: client is proxy, server does not know who proxy is;

Reverse proxy: The server is a proxy, and the client does not know who the proxy is.

nginx practical application scenarios: more suitable for stable services

Static resource server: js, css, html

Enterprise cluster

Daemon process: After exiting the command window, the service is always running;

Cluster multi-process scheduling model

Cluster is monitored by the master and distributed to each worker through round-robin algorithm to avoid the occurrence of panic phenomenon;

Round-robin scheduling algorithm is based on the principle that each request from the user is assigned to the internal server in turn;

cluster-model.js

const net = require ('net ');const fork = require ('child_process').fork; // cluster Simple version, cluster is based on child_process decapsulation;var workers = [];for (var i = 0; i

< 4; i++) { workers.push(fork('./child')); // cluster workers}var handle = net._createServerHandle('0.0.0.0', 3001); // masterhandle.listen();handle.onconnection = function(err, handle) { var worker = workers.pop(); worker.send({}, handle); workers.unshift(worker); // 通过pop 和 unshift实现一个简单的轮询}; child.js const net = require('net');process.on('message', (m, handle) =>

{ debugger; start(handle);});var buf = 'hello cluster';var res = ['HTTP/1.1 200 OK', 'content-length' + buf.length].join('\r\n') + '\r\n\r\n' + buf;function start(handle) { console.log('get a worker on server,pid = ' + process.pid); var socket = net.Socket({ handle }); socket.readable = socket.writable = true; // 修改socket的读写属性 socket.end(res);}cluster中的优雅退出

关闭异常worker进程所有的TCP server(将已有的快速断开，且不再接受新的连接)，断开和Master的IPC通道，不再接受新的用户请求;

Master立刻fork一个新的worker进程，保证总的进程数量不变;

异常worker等待一段时间，处理完已接受的请求后退出;

if(cluster.isMaster){ cluster.fork(); }else { // 出错之后 try{ res.end(dddd); // 报错，整个线程挂掉，不能提供服务， }catch(err){ // 断开连接，断开和Master的连接，守护进程其实就是重启; process.disconnect(); // or exit() } }进程守护

Master进程除了接收新的连接，分发给各worker处理之外，还像天使一样默默守护着这些进程，保障应用的稳定性，一旦某个worker进程退出就fork一个新的子进程顶替上去;

这一切cluster模块已经处理好了，当某个worker进程发生异常退出或者与Master进程失去联系(disconnected)时，master进程都会收到相应的事件通知;

cluster.on('exit',function(){ cluster.fork();})cluster.on('disconnect',function(){ cluster.fork();})IPC通信

IPC通信就是进程间的通信;

虽然每个worker进程是相对独立的，但是他们之间还是需要通信的;叫进程间通信(IPC)通信;

worker和worker之间的通信通过Master转发：通过worker的pid

const cluster = require('cluster');if(cluster.isMaster){ var worker = cluster.fork(); worker.send('hi, i am master'); worker.on('message', (msg) =>{ console.log(`${msg} is from worker ${worker.id}`) })}else if(cluster.isWorker){ process.on('message', (msg) =>{ process.send(msg); }) }上述内容就是nodejs中怎么利用cluster实现多进程，你们学到知识或技能了吗？如果还想学到更多技能或者丰富自己的知识储备，欢迎关注行业资讯频道。

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