cluster.on 上使用 babel 的 ES6 和 ES2016 之间的不同行为

Question

我正在尝试使用集群来利用拥有多核 CPU 的优势。使用代码：

var cluster = require('cluster');

if (cluster.isMaster) {
    for(var i = 0; i < 2; ++i) {
        cluster.fork();
    }
    cluster.on('exit', function (worker) {
        console.log('Worker ' + worker.process.pid + ' exitted.');
    });
} else {
    console.log('Worker ' + cluster.worker.process.pid);
    process.exit(0);
}

节点与输出完美配合

Worker 14058
Worker 14064
Worker 14058 exitted.
Worker 14064 exitted.

然而，当我尝试将 import 与 babel 一起使用时，我遇到了问题：

import *  as cluster from 'cluster'

if (cluster.isMaster) {
    for(let i = 0; i < 2; ++i) {
        cluster.fork();
    }
    cluster.on('exit', (worker) => console.log('Worker ' + worker.process.pid + ' exitted.'));
} else {
    console.log('Worker ' + cluster.worker.process.pid);
    process.exit(0);
}

节点的输出（在 babel 之后）是：

2.js:13
    cluster.on('exit', function (worker) {
            ^

TypeError: cluster.on is not a function
    at Object.<anonymous> (2.js:13:13)
    at Module._compile (module.js:556:32)
    at Object.Module._extensions..js (module.js:565:10)
    at Module.load (module.js:473:32)
    at tryModuleLoad (module.js:432:12)
    at Function.Module._load (module.js:424:3)
    at Module.runMain (module.js:590:10)
    at run (bootstrap_node.js:394:7)
    at startup (bootstrap_node.js:149:9)
    at bootstrap_node.js:509:3
Worker 14140
Worker 14146

这看起来很奇怪。我正在使用节点 v6.4.0，使用 babel 6.11.4 (babel-core 6.13.2)，.babelrc 的内容是：

{
  "presets": ["es2016", "es2015"]
}

知道发生了什么吗？

Answer 1

好的，我找到原因了，ref:

重点是把import * as cluster from 'cluster'改成import cluster from 'cluster'。

使用 import * as cluster from 'cluster'，所有可导出的内容都被导出到名称为 cluster 的对象中，它的结构为：

{ domain: null,
  _events: {},
  _eventsCount: 0,
  _maxListeners: undefined,
  Worker: 
   { [Function: Worker]
     super_: 
      { [Function: EventEmitter]
        EventEmitter: [Circular],
        usingDomains: false,
        defaultMaxListeners: 10,
        init: [Function],
        listenerCount: [Function] } },
  isWorker: false,
  isMaster: true,
  workers: {},
  settings: {},
  schedulingPolicy: 2,
  SCHED_NONE: 1,
  SCHED_RR: 2,
  setupMaster: [Function],
  fork: [Function],
  disconnect: [Function],
  default: 
   EventEmitter {
     domain: null,
     _events: {},
     _eventsCount: 0,
     _maxListeners: undefined,
     Worker: { [Function: Worker] super_: [Object] },
     isWorker: false,
     isMaster: true,
     workers: {},
     settings: {},
     schedulingPolicy: 2,
     SCHED_NONE: 1,
     SCHED_RR: 2,
     setupMaster: [Function],
     fork: [Function],
     disconnect: [Function] } }

另一方面，当 import cluster from 'cluster' 时，cluster 对象是默认导出：

EventEmitter {
  domain: null,
  _events: {},
  _eventsCount: 0,
  _maxListeners: undefined,
  Worker: 
   { [Function: Worker]
     super_: 
      { [Function: EventEmitter]
        EventEmitter: [Circular],
        usingDomains: false,
        defaultMaxListeners: 10,
        init: [Function],
        listenerCount: [Function] } },
  isWorker: false,
  isMaster: true,
  workers: {},
  settings: {},
  schedulingPolicy: 2,
  SCHED_NONE: 1,
  SCHED_RR: 2,
  setupMaster: [Function],
  fork: [Function],
  disconnect: [Function] }

Answer 2

require('babel-core/register')({
  presets: ['node6']
});

const app = require('./test.js');
app();

将您的代码保存在 test.js 中，看看神奇的东西

Answer 3

对我来说，我通过解构我从集群中需要的东西，一个一个地导入，它起作用了：

import { fork, on, isMaster } from 'cluster';

然后

   if (isMaster) {
      console.log(`Forking ${numWorkers} workers`);
      const workers = [...Array(numWorkers)].map(_ => fork());

      on('online', worker => console.log(`Worker ${worker.process.pid} is online`));
}

cluster.on 上使用 babel 的 ES6 和 ES2016 之间的不同行为

Different behavior between ES6 and ES2016 using babel on cluster.on

javascript

ecmascript-6

ecmascript-2016