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Building for Production

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I love our new setup! So it's time to talk about optimizing our build files for production. Yep, it's time to get serious, and make sure our files are minified and optimized to kick some performance butt!

Because, right now, if you check out the size of the build directory:

ls -la public/build

... yea! These files are pretty huge - rep_log.js is over 1 megabyte and so is layout.js! If you looked inside, you would find the problem immediately:

24 lines | assets/js/login.js
// ... lines 1 - 2
import $ from 'jquery';
// ... lines 4 - 24

jQuery is packaged individually inside each of these! That's super wasteful! Our users should only need to download jQuery one time.

The Shared Entry


The createdSharedEntry() feature still works great, but in the latest version of Encore, there is a new way to solve this problem called splitChunks(). Read about it here: https://symfony.com/doc/current/frontend/encore/split-chunks.html

No problem! Webpack has an awesome solution. Open webpack.config.js. Move the layout entry to the top - though, order doesn't matter. Now, change the method to createSharedEntry():

30 lines | webpack.config.js
// ... lines 1 - 3
// ... lines 5 - 10
.createSharedEntry('layout', './assets/js/layout.js')
// ... lines 12 - 25
// ... lines 27 - 30

Before we talk about this, move back to your terminal and restart Encore:

yarn run encore dev --watch

Then, I'll open a new tab - I love tabs! - and, when it finishes, check the file sizes again:

ls -la public/build

Woh! rep_log.js is down from 1 megabyte to 300kb! layout.js is still big because it does still contain jQuery. But login.js - which was almost 800kb is now... 4!

What is this magical shared entry!? To slightly over-simplify it, each project should have exactly one shared entry. And its JS file and CSS file should be included on every page.

When you set layout.js as a shared entry, any modules included in layout.js are not repeated in other files. For example, when Webpack sees that jquery is required by login.js, it says:

Hold on! jquery is already included in layout.js - the shared entry. So, I don't need to also put it in login.js.

It's a great solution to the duplication problem: if you have a library that is commonly used, just make sure that you import it in layout.js, even if you don't need it there. You can experiment with the right balance.

The manifest.js File

As soon as you do this, if you refresh, it works! I'm kidding - you'll totally get an error:

webpackJsonp is not defined

To fix that, in your base layout, right before layout.js, add one more script tag. Point it to a new build/manifest.js file:

107 lines | templates/base.html.twig
// ... lines 1 - 96
{% block javascripts %}
// ... lines 98 - 100
<script src="{{ asset('build/manifest.js') }}"></script>
<script src="{{ asset('build/layout.js') }}"></script>
{% endblock %}
// ... lines 104 - 107

The reason we need to do this is... well.. a bit technical. But basically, this helps with long-term caching, because it allows your giant layout.js file to change less often between deploys.

Production Build

Ok, this is great, but the files are still pretty big because they're not being minified. How can we tell Encore to do that? In your terminal, run:

yarn run encore production

That's it! This will take a bit longer: there's more magic happening behind the scenes. When it finishes, go back to your first open tab and run:

ls -la public/build

Let's check out the file sizes! The development rep_log.js that was 310kb is down to 74! Layout went from about 1Mb to 125kb. The CSS files are also way smaller. Yep, building for production is just one command: Encore handles all the details.

Adding Shortcut scripts

Oh, and here's a trick to be even lazier. Open package.json. I'm going to paste a new script section:

20 lines | package.json
"devDependencies": {
// ... lines 3 - 11
"scripts": {
"dev-server": "encore dev-server",
"dev": "encore dev",
"watch": "encore dev --watch",
"build": "encore production"

This gives you different shortcut commands for the different ways that you'll run Encore. Oh, we didn't talk about the dev-server, but it's another option for local development.

Anyways, now, in the terminal, we can just say:

yarn watch

Or any of the other script commands - like yarn build for production.

How to Deploy

Talking about production, there's one last big question we need to answer: how the heck do you deploy your assets to production? Do we need to install Node on the production server?

The answer is.... it depends. It depends on how sophisticated your deployment system is. Honestly, if you have a very simple deploy system - like a simple script, or maybe even some commands you run manually - then the easiest option is to install Node and yarn on your server and run encore production on your server after pulling down the latest files.

I know: this isn't a great solution: it's a bummer to install Node just for this reason. But, it is a valid option and totally simple.

A better solution is to run Encore on a different machine and then send the final, built files to your server. This highlights an important point: after you execute Encore, 100% of the files you need live in public/build. So, for example, after you execute:

yarn run encore production

you could send the public/build directory to your production machine and it would work perfectly. If you have a "build" server, that's a great place to run this command. Or, if you watched our Ansistrano Tutorial, you could run Encore locally, and use the copy module to deploy those files.

If you have any questions on your specific situation, you can ask us in the comments.