eightHundreds

Debugging ES6 in VS Code

My current editor of choice for all things related to Javascript and Node is VS Code, which I highly recommend. The other day I needed to hunt down a bug in one of my tests written in ES6, which at time of writing is not fully supported in Node. Shortly after, I found myself down the rabbit hole of debugging in VS Code and realized this isn't as straightforward as I thought initially. This short post summarizes the steps I took to make debugging ES6 in VS Code frictionless.

What doesn't work

My first approach was a launch configuration in launch.json mimicking tape -r babel-register ./path/to/testfile.js with babel configured to create inline sourcemaps in my package.json. The debugging started but breakpoints and stepping through the code in VS Code were a complete mess. Apparently, ad-hoc transpilation via babel-require-hook and inline sourcemaps do not work in VS Code. The same result for attaching (instead of launch) to `babel-node

Node.js异步处理CPU密集型任务

Node.js擅长数据密集型实时（data-intensive real-time）交互的应用场景。然而数据密集型实时应用程序并不是只有I/O密集型任务，当碰到CPU密集型任务时，比如要对数据加解密（node.bcrypt.js），数据压缩和解压（node-tar），或者要根据用户的身份对图片做些个性化处理，在这些场景下，主线程致力于做复杂的CPU计算，I/O请求队列中的任务就被阻塞。

Node.js主线程的event loop在处理所有的任务/事件时，都是沿着事件队列顺序执行的，所以在其中任何一个任务/事件本身没有完成之前，其它的回调、监听器、超时、nextTick()的函数都得不到运行的机会，因为被阻塞的event loop根本没机会处理它们，此时程序最好的情况是变慢，最糟的情况是停滞不动，像死掉一样。

一个可行的解决方案是新开进程，通过IPC通信，将CPU密集型任务交给子进程，子进程计算完毕后，再通过ipc消息通知主进程，并将结果返回给主进程。

和创建线程相比，开辟新进程的系统资源占用率大，进程间通信效率也不高。如果能不开新进程而是新开线程，将CPU耗时任务交给一个工作线程去做，然后主线程立即返回，处理其他的I/O请求，等到工作线程计算完毕后，通知主线程并将结果返回给主线程。那么在同时面对I/O密集型和CPU密集型服务的场景下，Node的主线程也会变得轻松，并能时刻保持高响应度。

	# -- coding:utf-8 --
	#!/usr/bin/python3

	import os
	import shutil
	import time
	import pymysql
	import requests
	from HTMLParser import HTMLParser
	from re import sub

	import * as React from 'react';
	import { Component } from 'react';

	export default function HOCBaseRender<Props, State, ComponentState>(
	Comp: new() => Component<Props & State, ComponentState>) {
	return class HOCBase extends Component<Props, State> {
	render() {
	return <Comp {...this.props} {...this.state}/>;
	}
	}