Interpretation of Nodejs multi-core processing module cluster

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About the author

Zhang Dan (Conan), programmer Java, R, PHP, Javascript
weibo ： @Conan_Z
blog: http://blog.fens.me
email: [email protected]

Please indicate the source for reprint:
http://blog.fens.me/nodejs-core-cluster/

Foreword
Everyone knows that nodejs is a single-process single-threaded server engine. No matter how powerful the hardware is, it can only use a single CPU for computing. Therefore, someone developed a third-party cluster, so that nodes can use multi-core CPUs to achieve parallelism.

With the development of nodejs, the production environment of nodejs must support multi-process and multi-core processing! In version V0.6.0, Nodejs has built-in cluster features. Since then, Nodejs can finally be seen as an independent application development solution.

content

Introduction to cluster
Simple use of cluster
How clusters work
API for cluster
Communication between master and worker
Using cluster to achieve load balancing (Load Balance) - win7 failed
Use cluster to achieve load balance (Load Balance) - ubuntu success
Test of cluster load balancing strategy

1. Cluster introduction

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

我的系统环境

win7 64bit
Nodejs:v0.10.5
Npm:1.2.19

在win的环境中，我们通过cluster启动多核的node提供web服务。

新建工程目录：


~ D:\workspace\javascript>mkdir nodejs-cluster && cd nodejs-cluster

新建文件：app.js


~ vi 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


~ D:\workspace\javascript\nodejs-cluster>node app.js

master start...
listening: worker 2368, Address: 0.0.0.0:57132
listening: worker 1880, Address: 0.0.0.0:57132
listening: worker 1384, Address: 0.0.0.0:57132
listening: worker 1652, Address: 0.0.0.0:57132

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。

1. 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。
2. 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
3. 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

官网地址：http://nodejs.org/api/cluster.html#cluster_cluster

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


~ vi 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);

}

控制台日志：


~ D:\workspace\javascript\nodejs-cluster>node cluster.js

[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


~ vi 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);
}

启动服务器：


~ D:\workspace\javascript\nodejs-cluster>node server.js
[master] start master...
[worker] start worker ...1
[worker] start worker ...2
[master] listening: worker1,pid:1536, Address:0.0.0.0:3000
[master] listening: worker2,pid:5920, Address:0.0.0.0:3000
[worker] start worker ...3
[master] listening: worker3,pid:7156, Address:0.0.0.0:3000
[worker] start worker ...4
[master] listening: worker4,pid:2868, Address:0.0.0.0:3000
worker4
worker4
worker4
worker4
worker4
worker4
worker4
worker4

用curl工具访问


C:\Users\Administrator>curl localhost:3000
worker4,PID:2868
C:\Users\Administrator>curl localhost:3000
worker4,PID:2868
C:\Users\Administrator>curl localhost:3000
worker4,PID:2868
C:\Users\Administrator>curl localhost:3000
worker4,PID:2868
C:\Users\Administrator>curl localhost:3000
worker4,PID:2868
C:\Users\Administrator>curl localhost:3000
worker4,PID:2868
C:\Users\Administrator>curl localhost:3000
worker4,PID:2868
C:\Users\Administrator>curl localhost:3000
worker4,PID:2868

我们发现了cluster在win中的bug，只用到worker4。果断切换到Linux测试。

7. 用cluster实现负载均衡(Load Balance) -- ubuntu成功

Linux的系统环境

Linux: Ubuntu 12.04.2 64bit Server
Node: v0.11.2
Npm: 1.2.21

Building the project: not much explanation


~ cd :/home/conan/nodejs/
~ mkdir nodejs-cluster && cd nodejs-cluster
~ vi 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);
}

start the server


conan@conan-deskop:~/nodejs/nodejs-cluster$ node server.js
[master] start master...
[worker] start worker ...1
[master] listening: worker1,pid:2925, Address:0.0.0.0:3000
[worker] start worker ...3
[master] listening: worker3,pid:2931, Address:0.0.0.0:3000
[worker] start worker ...4
[master] listening: worker4,pid:2932, Address:0.0.0.0:3000
[worker] start worker ...2
[master] listening: worker2,pid:2930, Address:0.0.0.0:3000
worker4
worker2
worker1
worker3
worker4
worker2
worker1

Access with curl tool


C:\Users\Administrator>curl 192.168.1.20:3000
worker4,PID:2932
C:\Users\Administrator>curl 192.168.1.20:3000
worker2,PID:2930
C:\Users\Administrator>curl 192.168.1.20:3000
worker1,PID:2925
C:\Users\Administrator>curl 192.168.1.20:3000
worker3,PID:2931
C:\Users\Administrator>curl 192.168.1.20:3000
worker4,PID:2932
C:\Users\Administrator>curl 192.168.1.20:3000
worker2,PID:2930
C:\Users\Administrator>curl 192.168.1.20:3000
worker1,PID:2925

In a Linux environment, the cluster is running correctly! ! !

8. Test of cluster load balancing strategy

We are under Linux, completed the test, and used the test software: siege

install siege

~ sudo apt-get install siege

start node cluster

~ node server.js > server.log

Run the siege start command, 50 concurrent requests per second.


~ sudo siege -c 50 http://localhost:3000

HTTP/1.1 200   0.00 secs:      16 bytes ==> /
HTTP/1.1 200   0.00 secs:      16 bytes ==> /
HTTP/1.1 200   0.00 secs:      16 bytes ==> /
HTTP/1.1 200   0.01 secs:      16 bytes ==> /
HTTP/1.1 200   0.00 secs:      16 bytes ==> /
HTTP/1.1 200   0.00 secs:      16 bytes ==> /
HTTP/1.1 200   0.00 secs:      16 bytes ==> /
HTTP/1.1 200   0.01 secs:      16 bytes ==> /
HTTP/1.1 200   0.00 secs:      16 bytes ==> /
HTTP/1.1 200   0.00 secs:      16 bytes ==> /
HTTP/1.1 200   0.00 secs:      16 bytes ==> /
HTTP/1.1 200   0.02 secs:      16 bytes ==> /
HTTP/1.1 200   0.00 secs:      16 bytes ==> /
HTTP/1.1 200   0.02 secs:      16 bytes ==> /
HTTP/1.1 200   0.01 secs:      16 bytes ==> /
HTTP/1.1 200   0.01 secs:      16 bytes ==> /
.....

^C
Lifting the server siege...      done.                                                                Transactions:                    3760 hits
Availability:                 100.00 %
Elapsed time:                  39.66 secs
Data transferred:               0.06 MB
Response time:                  0.01 secs
Transaction rate:              94.81 trans/sec
Throughput:                     0.00 MB/sec
Concurrency:                    1.24
Successful transactions:        3760
Failed transactions:               0
Longest transaction:            0.20
Shortest transaction:           0.00

FILE: /var/siege.log
You can disable this annoying message by editing
the .siegerc file in your home directory; change
the directive 'show-logfile' to false.

We counted the results and executed 3760 requests, consuming 39.66 seconds, and processing 94.81 requests per second.

View the server.log file,


~  ls -l
total 64
-rw-rw-r-- 1 conan conan   756  9月 28 15:48 server.js
-rw-rw-r-- 1 conan conan 50313  9月 28 16:26 server.log

~ tail server.log
worker4
worker1
worker2
worker4
worker1
worker2
worker4
worker3
worker2
worker1

Finally, analyze it in R language: server.log


~ R 

> df<-read.table(file="server.log",skip=9,header=FALSE)
> summary(df)
       V1
 worker1:1559
 worker2:1579
 worker3:1570
 worker4:1535

We see that requests are distributed to workers with a comparable amount of data. Therefore, the cluster's load balancing strategy should be randomly assigned.

Well, we learned another useful skill! Using cluster, you can build multi-core applications and make full use of the performance of multi-CPU belt industry! !