HappyPack makes webpack builds faster by allowing you to transform multiple files in parallel.
See "How it works" below for more details.
- webpack initial build times are horrifying in large codebases (3k+ modules)
- something that works for one-time builds (e.g. CI) and for continuous ones
(i.e.
--watchduring development)
npm install --save-dev happypack
In your webpack.config.js, you need to use the plugin and tell it of the
loaders it should use to transform the sources.
var HappyPack = require('happypack');
exports.plugins = [
new HappyPack({
// loaders is the only required parameter:
loaders: [ 'babel?presets[]=es2015' ],
// customize as needed, see Configuration below
})
];Now you replace your current loaders with HappyPack's loader:
exports.module = {
loaders: {
test: /.js$/,
loaders: [ 'happypack/loader' ],
include: [
// ...
],
}
};That's it. Now sources that match .js$ will be handed off to happypack which
will transform them in parallel using the loaders you specified.
These are the parameters you can pass to the plugin when you instantiate it.
Each loader entry consists of the name or path of loader that would
transform the files and an optional query string to pass to it. This looks
similar to what you'd pass to webpack's loader config.
Heads up!
HappyPack doesn't work with all webpack loaders as some loader API are not supported.
See this wiki page for more details on current Loader API support.
A unique id for this happy plugin. This is used by the loader to know which plugin it's supposed to talk to.
Normally, you would not need to specify this unless you have more than one HappyPack plugin defined, in which case you'll need distinct IDs to tell them apart. See "Using multiple instances" below for more information on that.
Defaults to: "1"
This number indicates how many Node VMs HappyPack will spawn for compiling the source files. After a lot of tinkering, I found 4 to yield the best results. There's certainly a diminishing return on this value and increasing beyond 8 actually slowed things down for me.
Keep in mind that this is only relevant when performing the initial build
as HappyPack will switch into a synchronous mode afterwards (i.e. in watch
mode.)
Defaults to: 3
A custom thread-pool to use for retrieving worker threads. Normally, this
is managed internally by each HappyPlugin instance, but you may override
this behavior for better results.
See "Shared thread pools" below for more information about this.
Defaults to: null
Enable this to log status messages from HappyPack to STDOUT like start-up banner, etc..
Defaults to: true
Enable this if you want happypack to still produce its output even when you're
doing a webpack --profile run. Since this variable was introduced, happypack
will be silent when doing a profile build in order not to corrupt any JSON
output by webpack (i.e. when using --json as well.)
Defaults to: false
Enable this to log diagnostic messages from HappyPack to STDOUT. Useful for troubleshooting.
Defaults to: false
HappyPack sits between webpack and your primary source files (like JS sources) where the bulk of loader transformations happen. Every time webpack resolves a module, HappyPack will take it and all its dependencies and distributes those files to multiple worker "threads".
Those threads are actually simple node processes that invoke your transformer. When the compiled version is retrieved, HappyPack serves it to its loader and eventually your chunk.
It's possible to define multiple HappyPack plugins for different types of sources/transformations. Just pass in a unique id for each plugin and make sure you pass it their loaders. For example:
// @file webpack.config.js
exports.plugins = [
new HappyPack({
id: 'jsx',
threads: 4,
loaders: [ 'babel-loader' ]
}),
new HappyPack({
id: 'coffeescripts',
threads: 2,
loaders: [ 'coffee-loader' ]
})
];
exports.module.loaders = [
{
test: /\.js$/,
loaders: [ 'happypack/loader?id=jsx' ]
},
{
test: /\.coffee$/,
loaders: [ 'happypack/loader?id=coffeescripts' ]
},
]Now .js files will be handled by the first Happy plugin which will use
babel-loader to transform them, while .coffee files will be handled
by the second one using the coffee-loader as a transformer.
Normally, each HappyPlugin instance you create internally manages its own
threads which are used to compile sources. However, if you have a number of
plugins, it can be more optimal to create a thread pool yourself and then
configure the instances to share that pool, minimizing the idle time of
threads within it.
Here's an example of using a custom pool of 5 threads that will be shared between loaders for both JS and SCSS/LESS/whatever sources:
// @file: webpack.config.js
var HappyPack = require('happypack');
var happyThreadPool = HappyPack.ThreadPool({ size: 5 });
module.exports = {
// ...
plugins: [
new HappyPack({
id: 'js',
threadPool: happyThreadPool,
loaders: [ 'babel-loader' ]
}),
new HappyPack({
id: 'styles',
threadPool: happyThreadPool,
loaders: [ 'style-loader', 'css-loader', 'less-loader' ]
})
]
};For the main repository I tested on, which had around 3067 modules, the build time went down from 39 seconds to a whopping ~10 seconds.
Here's a rundown of the various states the build was performed in:
| Elapsed (ms) | Happy? | Using DLLs? |
|---|---|---|
| 39851 | NO | NO |
| 37393 | NO | YES |
| 14605 | YES | NO |
| 13925 | YES | NO |
| 11877 | YES | NO |
| 9228 | YES | YES |
The builds above were run under Linux on a machine with 12 cores.
See ./CHANGELOG.md.
As of version 3.0.3, it does to a certain extent. You can look at the pending issues to see if any of those affect you.
If you come across an issue that is exclusive to webpack 2, a fix has to be provided by the community (or you) as the author currently has no plans for providing webpack 2 support.
The short answer is: yes, it finally does! The longer answer is that you need to use ts-loader in "transpiling-only" mode then use the special plugin fork-ts-checker-notifier-webpack-plugin to perform static type checking.
More information can be found in this wiki article, in the ts-loader "happypack mode" section and you can refer to the example that shows this in action.
Huge thanks to @johnnyreilly, @aindlq, @piotr-oles, @abergs and many others for making this work.
We're keeping track of known loader support in this wiki page. Some loaders may require extra configuration to make them work.
If the loader you're trying to use isn't listed there, you can refer to this wiki page to see which loader APIs are supported. If your loader uses any API that is NOT supported, chances are that it will not work with HappyPack.
There have been a few reports (e.g GH-99 and GH-70) that it does not.
It's difficult for me to confirm or to troubleshoot as I have no access to such an environment. If you do and are willing to help, please do!
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