NodeJS多核处理模cluster解读

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发布于 2018-08-27 06:53:43

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参考 http://blog.fens.me/nodejs-core-cluster/

大家都知道nodejs是一个单进程单线程的服务器引擎，不管有多么的强大硬件，只能利用到单个CPU进行计算。所以，有人开发了第三方的cluster，让node可以利用多核CPU实现并行。

1. cluster介绍

cluster是一个nodejs内置的模块，用于nodejs多核处理。cluster模块，可以帮助我们简化多进程并行化程序的开发难度，轻松构建一个用于负载均衡的集群。

2. cluster的简单使用

在win的环境中，我们通过cluster启动多核的node提供web服务。新建文件：app.js

var cluster = require('cluster');
var http = require('http');
var numCPUs = require('os').cpus().length;

if (cluster.isMaster) {
    console.log("master start...");

    // Fork workers.
    for (var i = 0; i < numCPUs; i++) {
        cluster.fork();
    }

    cluster.on('listening',function(worker,address){
        console.log('listening: worker ' + worker.process.pid +', Address: '+address.address+":"+address.port);
    });

    cluster.on('exit', function(worker, code, signal) {
        console.log('worker ' + worker.process.pid + ' died');
    });
} else {
    http.createServer(function(req, res) {
        res.writeHead(200);
        res.end("hello world\n");
    }).listen(0);
}

在控制台启动node程序

λ node server.js
master start...
listening: worker 12976, Address: null:50047
listening: worker 14716, Address: null:50047
listening: worker 14184, Address: null:50047
listening: worker 14820, Address: null:50047

master是总控节点，worker是运行节点。然后根据CPU的数量，启动worker。我本地是双核双通道的CPU，所以被检测为4核，启动了4个worker。

3. cluster的工作原理

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

当worker使用server.listen（...）函数时，将参数序列传递给master进程。如果master进程已经匹配workers，会将传递句柄给工人。如果master没有匹配好worker，那么会创建一个worker，再传递并句柄传递给worker。

在边界条件，有3个有趣的行为：注：下面server.listen()，是对底层“http.Server-->net.Server”类的调用。

server.listen({fd: 7}):在master和worker通信过程，通过传递文件，master会监听“文件描述为7”，而不是传递“文件描述为7”的引用。
server.listen(handle):master和worker通信过程，通过handle函数进行通信，而不用进程联系
server.listen(0):在master和worker通信过程，集群中的worker会打开一个随机端口共用，通过socket通信，像上例中的57132 当多个进程都在 accept() 同样的资源的时候，操作系统的负载均衡非常高效。Node.js没有路由逻辑，worker之间没有共享状态。所以，程序要设计得简单一些，比如基于内存的session。

因为workers都是独力运行的，根据程序的需要，它们可以被独立删除或者重启，worker并不相互影响。只要还有workers存活，则master将继续接收连接。Node不会自动维护workers的数目。我们可以建立自己的连接池。

4. cluster的API

cluster对象 cluster的各种属性和函数 cluster.setttings:配置集群参数对象 cluster.isMaster:判断是不是master节点 cluster.isWorker:判断是不是worker节点 Event: 'fork': 监听创建worker进程事件 Event: 'online': 监听worker创建成功事件 Event: 'listening': 监听worker向master状态事件 Event: 'disconnect': 监听worker断线事件 Event: 'exit': 监听worker退出事件 Event: 'setup': 监听setupMaster事件 cluster.setupMaster([settings]): 设置集群参数 cluster.fork([env]): 创建worker进程 cluster.disconnect([callback]): 关闭worket进程 cluster.worker: 获得当前的worker对象 cluster.workers: 获得集群中所有存活的worker对象

worker对象 worker的各种属性和函数：可以通过cluster.workers, cluster.worket获得。 worker.id: 进程ID号 worker.process: ChildProcess对象 worker.suicide: 在disconnect()后，判断worker是否自杀 worker.send(message, [sendHandle]): master给worker发送消息。注：worker给发master发送消息要用process.send(message) worker.kill([signal='SIGTERM']): 杀死指定的worker，别名destory() worker.disconnect(): 断开worker连接，让worker自杀 Event: 'message': 监听master和worker的message事件 Event: 'online': 监听指定的worker创建成功事件 Event: 'listening': 监听master向worker状态事件 Event: 'disconnect': 监听worker断线事件 Event: 'exit': 监听worker退出事件

5. master和worker的通信

实现cluster的API，让master和worker相互通信。新建文件: cluster.js

var cluster = require('cluster');
var http = require('http');
var numCPUs = require('os').cpus().length;

if (cluster.isMaster) {
    console.log('[master] ' + "start master...");

    for (var i = 0; i < numCPUs; i++) {
        var wk = cluster.fork();
        wk.send('[master] ' + 'hi worker' + wk.id);
    }

    cluster.on('fork', function (worker) {
        console.log('[master] ' + 'fork: worker' + worker.id);
    });

    cluster.on('online', function (worker) {
        console.log('[master] ' + 'online: worker' + worker.id);
    });

    cluster.on('listening', function (worker, address) {
        console.log('[master] ' + 'listening: worker' + worker.id + ',pid:' + worker.process.pid + ', Address:' + address.address + ":" + address.port);
    });

    cluster.on('disconnect', function (worker) {
        console.log('[master] ' + 'disconnect: worker' + worker.id);
    });

    cluster.on('exit', function (worker, code, signal) {
        console.log('[master] ' + 'exit worker' + worker.id + ' died');
    });

    function eachWorker(callback) {
        for (var id in cluster.workers) {
            callback(cluster.workers[id]);
        }
    }

    setTimeout(function () {
        eachWorker(function (worker) {
            worker.send('[master] ' + 'send message to worker' + worker.id);
        });
    }, 3000);

    Object.keys(cluster.workers).forEach(function(id) {
        cluster.workers[id].on('message', function(msg){
            console.log('[master] ' + 'message ' + msg);
        });
    });

} else if (cluster.isWorker) {
    console.log('[worker] ' + "start worker ..." + cluster.worker.id);

    process.on('message', function(msg) {
        console.log('[worker] '+msg);
        process.send('[worker] worker'+cluster.worker.id+' received!');
    });

    http.createServer(function (req, res) {
            res.writeHead(200, {"content-type": "text/html"});
            res.end('worker'+cluster.worker.id+',PID:'+process.pid);
    }).listen(3000);

}

输出信息如下：

[master] start master...
[worker] start worker ...1
[worker] [master] hi worker1
[worker] start worker ...2
[worker] [master] hi worker2
[master] fork: worker1
[master] fork: worker2
[master] fork: worker3
[master] fork: worker4
[master] online: worker1
[master] online: worker2
[master] message [worker] worker1 received!
[master] message [worker] worker2 received!
[master] listening: worker1,pid:6068, Address:0.0.0.0:3000
[master] listening: worker2,pid:1408, Address:0.0.0.0:3000
[master] online: worker3
[worker] start worker ...3
[worker] [master] hi worker3
[master] message [worker] worker3 received!
[master] listening: worker3,pid:3428, Address:0.0.0.0:3000
[master] online: worker4
[worker] start worker ...4
[worker] [master] hi worker4
[master] message [worker] worker4 received!
[master] listening: worker4,pid:6872, Address:0.0.0.0:3000
[worker] [master] send message to worker1
[worker] [master] send message to worker2
[worker] [master] send message to worker3
[worker] [master] send message to worker4
[master] message [worker] worker1 received!
[master] message [worker] worker2 received!
[master] message [worker] worker3 received!
[master] message [worker] worker4 received!

6. 用cluster实现负载均衡(Load Balance) -- win7失败

新建文件: server.js

var cluster = require('cluster');
var http = require('http');
var numCPUs = require('os').cpus().length;

if (cluster.isMaster) {
    console.log('[master] ' + "start master...");

    for (var i = 0; i < numCPUs; i++) {
         cluster.fork();
    }

    cluster.on('listening', function (worker, address) {
        console.log('[master] ' + 'listening: worker' + worker.id + ',pid:' + worker.process.pid + ', Address:' + address.address + ":" + address.port);
    });

} else if (cluster.isWorker) {
    console.log('[worker] ' + "start worker ..." + cluster.worker.id);
    http.createServer(function (req, res) {
        console.log('worker'+cluster.worker.id);
        res.end('worker'+cluster.worker.id+',PID:'+process.pid);
    }).listen(3000);
}