Node.js中的cluster模块深入解读

const http = require('http');
http.createServer((req, res) => {
 res.writeHead(200);
 res.end('hello world\n');
}).listen(8000);

// 启动第一个服务 node index.js &
// 启动第二个服务 node index.js &

 throw er; // Unhandled 'error' event
 ^

Error: listen EADDRINUSE :::8000
 at Server.setupListenHandle [as _listen2] (net.js:1330:14)
 at listenInCluster (net.js:1378:12)
 at Server.listen (net.js:1465:7)
 at Object.<anonymous> (/Users/xiji/workspace/learn/node-basic/cluster/simple.js:5:4)
 at Module._compile (internal/modules/cjs/loader.js:702:30)
 at Object.Module._extensions..js (internal/modules/cjs/loader.js:713:10)
 at Module.load (internal/modules/cjs/loader.js:612:32)
 at tryModuleLoad (internal/modules/cjs/loader.js:551:12)
 at Function.Module._load (internal/modules/cjs/loader.js:543:3)
 at Function.Module.runMain (internal/modules/cjs/loader.js:744:10)

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

if (cluster.isMaster) {
 console.log(`Master ${process.pid} is running`);

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

 cluster.on('exit', (worker, code, signal) => {
 console.log(`worker ${worker.process.pid} died`);
 });
} else {
 // Workers can share any TCP connection
 // In this case it is an HTTP server
 http.createServer((req, res) => {
 res.writeHead(200);
 res.end('hello world\n');
 }).listen(8000);

 console.log(`Worker ${process.pid} started`);
}

// node index.js 执行完启动了一个主进程和8个子进程(子进程数与cpu核数相一致)
Master 11851 is running
Worker 11852 started
Worker 11854 started
Worker 11853 started
Worker 11855 started
Worker 11857 started
Worker 11858 started
Worker 11856 started
Worker 11859 started

function listenInCluster(server, address, port, addressType, backlog, fd, excluseive) {
 
 if (cluster.isMaster || exclusive) {
 server._listen2(address, port, addressType, backlog, fd);
 return;
 }

 const serverQuery = { address: address ......};

 cluster._getServer(server, serverQuery, listenOnMasterHandle);

 function listenOnMasterHandle(err, handle) {
 server._handle = handle;
 server._listen2(address, port, addressType, backlog, fd);
 }
}

cluster._getServer = function(obj, options, cb) {
 ...
 const message = util._extend({
 act: 'queryServer',
 index: indexes[indexesKey],
 data: null
 }, options);

 message.address = address;

 send(message, (reply, handle) => {
 if (handle)
 shared(reply, handle, indexesKey, cb); // Shared listen socket.
 else
 rr(reply, indexesKey, cb); // Round-robin.
 });
 ...
};

function rr(message, indexesKey, cb) {

 var key = message.key;

 function listen(backlog) {
 return 0;
 }

 function close() {
 if (key === undefined)
 return;

 send({ act: 'close', key });
 delete handles[key];
 delete indexes[indexesKey];
 key = undefined;
 }

 function getsockname(out) {
 if (key)
 util._extend(out, message.sockname);

 return 0;
 }

 const handle = { close, listen, ref: noop, unref: noop };
 handles[key] = handle;
 cb(0, handle);
}

NODE_CLUSTER_SCHED_POLICY='rr'
NODE_CLUSTER_SCHED_POLICY='none'

cluster.schedulingPolicy = cluster.SCHED_NONE;
cluster.schedulingPolicy = cluster.SCHED_RR;

RoundRobinHandle.prototype.distribute = function(err, handle) {
 this.handles.push(handle);
 const worker = this.free.shift();

 if (worker) {
 this.handoff(worker);
 }
};

RoundRobinHandle.prototype.handoff = function(worker) {
 const handle = this.handles.shift();
 if (handle === undefined) {
 this.free.push(worker); // Add to ready queue again.
 return;
 }

 const message = { act: 'newconn', key: this.key };
 sendHelper(worker.process, message, handle, (reply) => {
 if (reply.accepted)
 handle.close();
 else
 this.distribute(0, handle); // Worker is shutting down. Send to another.
 this.handoff(worker);
 });
};