Slow production build

[trungdq88]

Not sure if the project is too large or there is something wrong, but my yarn run build took almost 5 minutes.

The project is about 1k5 files:

git ls-files | wc -l
1540

Is it normal? Is there any --debug option to verbosely view the time took to compile the project?

[gaearon]

We'll switch to Webpack 3 soon which will be a tad faster.
Unfortunately there's only so much we can do when underlying tools are slow 😢

I see you're using code splitting—maybe this could help? webpack/webpack#4636 (comment) I'm not sure how exactly you're using it.

Other than that, I don't really have good news for you. You can contribute to webpack to make it faster, or maybe investigate approaches like HappyPack and whether we could switch to them.

[viankakrisna]

I think we can do more to improve build speed. cache-loader improvement can be seen on a large set of files. it cuts about 20-30 seconds on my project. (usually it takes about 90 - 100s) Webpack's UglifyJS plugin can be replaced with https://www.npmjs.com/package/webpack-uglify-parallel and it combined with the cache-loader cuts almost 50% of the build time.

And then there's @asfktz autodll plugin https://github.com/asfktz/autodll-webpack-plugin/. I haven't tested it with a real project, but it's nice to work with him on improving this :)

And at the very least, maybe we can add tests that track how long the build gonna take, with a large number of files.

[viankakrisna]

Switching this internally would, of course, affects stability, maybe we can have a canary channel to test out this? At least, a canary channel of CRA would have more users than an obscurely published fork.

Or have a way to easily install from GitHub branches, without modifying package name etc. In my experience maintaining a fork is hard, especially if I need to modify something that is not in react-scripts. Sometimes when syncing the package name is overwritten, imports are rewritten, etc2

[Timer]

How long does yarn start take for your project?
If it's ~1 minute, I'd love to get my hands on your project if you'd be willing to share it.

[trungdq88]

@Timer yarn start takes about 2~3 minutes. The project is private so I can't share it 😞

[Timer]

Most client side code isn't very private, 😛.
I could sign an NDA or something similar if needed.

Is this app deployed on the web so I could take a peek?

[trungdq88]

The app is deployed on the web but can only access via a VPN. It's a huge Admin Panel app for an internal product.

I could talk to the team to see if I can grant you a read permission, would you still willing to take a look if I can get the agreement from the team?

[Timer]

Sure! I would love to have temporary access to the code base to test optimizations against. Build speed is something we're very interested in speeding up.

[miraage]

@viankakrisna uglifyjs plugin now supports parallel out-of-the-box.

https://github.com/webpack-contrib/uglifyjs-webpack-plugin/#parallel

[Timer]

@trungdq88 any word on that repo? 😄

[trungdq88]

@Timer sorry for being inactive. It is under consideration and we need sometime to prepare something like NDA (we have never done this before). Hopefully I can have the answer for you in the next 2 days.

[Timer]

I'm going to be out of town until next week, just a heads up! So no rush.

[viankakrisna]

@miraage can we enable it with our current webpack version?

[miraage]

@viankakrisna it works for me like a charm in my pet project (webpack 3.4). The problem is that plugin currently in beta status.

[Timer]

We'll hold off on enabling it until it's considered stable. :)

[viankakrisna]

I wish CRA has an experimental version, just to test cutting edge feature with lots of user and case 😄

[themre]

@viankakrisna yeah I also wouldn't mind having some fork with latest features :D

[viankakrisna]

It should be promoted "officially" by CRA so more people can test drive it :)

[trungdq88]

Updated to react-scripts 1.0.11 today (with webpack 3), build time reduced from 280s -> 175s. That's something :)

[gaearon]

Nice, thanks for checking! You can also add GENERATE_SOURCEMAP=false to .env file if you're okay with missing sourcemaps. This should make it faster yet. (But I don't recommend skipping sourcemaps because then you can't debug production errors.)

[gaearon]

I wish CRA has an experimental version

File an issue for this? I'm not opposed to having an opt in way to beta test features before they're enabled for everybody.

[mwakerman]

Setting GENERATE_SOURCEMAP=false cut down our build time by about a third.

[miraage]

Disabling eslint preloader also decreases build time.

[rclai]

How do you guys disable eslint?

[viankakrisna]

^ ejecting?

found an interesting issue about eslint-loader / eslint perf webpack-contrib/eslint-loader#206

[gaearon]

@viankakrisna Good find

[rclai]

Is there no way to disable eslint via an environment variable when building without ejecting?

[sazzer]

Any movement on this? I've got a project where the CRA Build is the overwhelming majority of the time. It's a Maven project - the CRA app is the frontend for a Java webapp. The entire Maven build for my frontend takes 40s, including:

• yarn install - 0.78s
• yarn build - 31s
• yarn flow - 0.23s
• yarn test - 5s

So just building the production frontend files is over 3/4 of the build time.

This is using CRA as it comes, with no ejecting or anything like that, and only has 26 source files.

[sidoruk-sv]

Installed new CRA@next (npx create-react-app@next --scripts-version=2.0.0-next.9754a231) - npm run build time decrease:

Old setup:
npm run build 75.44s user 2.76s system 123% cpu 1:03.35 total

New setup:
npm run build 170.59s user 9.72s system 238% cpu 1:15.61 total

Environment:

• project is ejected;
• Node: v9.8.0
• NPM: v5.6.0
• machine: MacBook Pro 15 (2013), Intel Core i7 2.3 GHz (4 cores), RAM: 16 GB, SSD

I can provide full config difference from default 2.0.0-next.9754a231 setup on request.

[Timer]

The bulk of all optimizations have made it into the 2.0 beta, barring webpack 4.

@sidoruk-sv if you're reporting a build time regression, please open a new issue.

[sidoruk-sv]

@Timer one more thing)

That was my misunderstanding of time output (looked at user time, but should on total)

So tried latest: npx create-react-app@next --scripts-version=2.0.0-next.b2fd8db8

and re-check build time for old and new configs:

Old:
time npm run build:


• npm run build 72.09s user 2.52s system 122% cpu 1:00.88 total
• npm run build 70.55s user 2.51s system 125% cpu 58.098 total

gtime npm run build:


• 69.45user 2.50system 0:56.86elapsed 126%CPU

New:

time npm run build:

• npm run build 98.71s user 5.29s system 266% cpu 39.096 total
• npm run build 102.98s user 5.95s system 283% cpu 38.404 total

gtime npm run build:

• 105.72user 5.40system 0:42.46elapsed 261%CPU
• 100.73user 6.09system 0:37.64elapsed 283%CPU


So build time (total/elapsed) decrease by ~10-20s

(for my config)

You guys are cool!
You make continuous improvements that enhance the quality of developer's life, thanks for your work.

[Timer]

Neat. The next 2.0 release will be even quicker, stay tuned!

[ApacheEx]

I was playing with webpackChunkName and my build time was decreased from ~3 mins to 34 sec. 🚀

I'm using react-loadable for all dynamic imports, but somehow build time was weird (because of many components). So, I have replaced this:

loader: () => import(`components/${component}`)

to:

loader: () => import(/* webpackChunkName: "components/[request]" */ `components/${component}`)

and as result: almost in 6x times build time is faster now. Hope it will help somebody.

p.s. more info about import here: https://webpack.js.org/api/module-methods/#import-

[viankakrisna]

interesting, can that comment be inserted automatically with a babel plugin / other wizardry?

[dotku]

I can se react-script is using webpack 3 right now, but I feel that it is still slow, do you think we should have automatically build to ignore the waiting time?

[pans0930]

@Timer one more thing)

That was my misunderstanding of time output (looked at user time, but should on total)

So tried latest: npx create-react-app@next --scripts-version=2.0.0-next.b2fd8db8

and re-check build time for old and new configs:

Old:
time npm run build:


• npm run build 72.09s user 2.52s system 122% cpu 1:00.88 total
• npm run build 70.55s user 2.51s system 125% cpu 58.098 total

gtime npm run build:


• 69.45user 2.50system 0:56.86elapsed 126%CPU

New:

time npm run build:

• npm run build 98.71s user 5.29s system 266% cpu 39.096 total
• npm run build 102.98s user 5.95s system 283% cpu 38.404 total

gtime npm run build:

• 105.72user 5.40system 0:42.46elapsed 261%CPU
• 100.73user 6.09system 0:37.64elapsed 283%CPU


So build time (total/elapsed) decrease by ~10-20s

(for my config)

You guys are cool!
You make continuous improvements that enhance the quality of developer's life, thanks for your work.

do you solve the build slowly?Thank you!