rails webpacker:compile very slow compared to bin/webpack

[scottrobertson]

We have been having an issue for a while now with our production builds taking 4+ minutes, compared to ~30s locally.

I assumed until now that this was an issue with CI resources, however, I have since found that running bin/webpack is a huge amount faster. See below:

bundle exec rails webpacker:compile

Hash: fae915c931e9f41b0499
Version: webpack 4.42.1
Time: 211332ms
Built at: 29/04/2020 13:14:22

bin/webpack

Hash: 7ab04632a7b9a483ef83
Version: webpack 4.42.1
Time: 58670ms
Built at: 29/04/2020 13:16:03

I am clearing tmp/cache and public/packs between builds.

Any suggestions on how to debug this?

I can replicate this consistently locally, and on CI.

[scottrobertson]

Looks like no css is extracted when running bin/webpack, so that probably explains why it's slower.

Will debug some more.

[scottrobertson]

Hash: 0e4cfc914194c2c6e9e7
Version: webpack 4.42.1
Time: 225482ms
Built at: 04/29/2020 12:44:54 PM

with extract_css set to false, so it's not that.

[scottrobertson]

bin/webpack --config config/webpack/production.js

Is just as slow as bundle exec rails webpacker:compile, so it's something in our configs by the looks of it.

[dkniffin]

@scottrobertson I'm seeing this behavior on my app now. Did you track down what was causing this? Is it safe to just run bin/webpack instead of bin/rails webpacker:compile? I wonder if it's simply because it has to load up the whole Rails environment again?

[scottrobertson]

The main issue for us was we were building within a docker environment on CircleCI. Switching that to a machine instead resolved most speed issues.

[trackedsupport]

Same thing is happening for me all of a sudden, not sure what I've changed.

But its 10 seconds vs 68 seconds.

Its causing puma-dev to take forever.