In short, baler is an AMD (https://requirejs.org/) module bundler and preloader for Magento 2 stores.
How Does it Work?
The "core" bundle contains the code that baler can determine is critical to the first render of the page. This includes the Magento core libraries, along with some theme-specific and feature-specific code.
This is where Graph Preloading comes in. When baler is run, it crawls the file system and determines which .phtml are eligible to be used in a specific area (frontend/adminhtml/base). These templates are then analyzed for any AMD module dependencies.
When a graph of dependencies has been collected for each .phtml file, the lists are flattened and deduped against the "core" bundle. Then, when a shopper requests a page of your store, preload tags are injected that instruct the browser to immediately begin fetching necessary dependencies.
I've tested on latest Magento 2.3.3 CE version, and you can check page load results here https://magentocommand.ml
It does what it says in manual, creating one core-bundle.js containing all possible aspects from core side which can be bundled safely.
So let me show today how I did it on Fresh Magento 2.3.3 CE version with default Luma theme.
1) We need to clone current Baler repository:
git clone https://github.com/magento/baler.git
2) You can cd into baler folder and install it using npm
3) Optionally, if you don't wish to get anything installed on your local server there is already ready made binary file within bin/ folder named baler.
4) Make sure that you have node.js version >= 10.12.0 installed.
~/baler/bin$ ./baler baler requires a version of node.js >= 10.12.0. You're currently using v8.16.0
This can be fixed easily by downloading latest Node version:
wget -c https://nodejs.org/dist/v10.14.1/node-v10.14.1-linux-x64.tar.gz
Then let's unpack archive:
tar -xvf node-v10.14.1-linux-x64.tar.gz
Once extracted we can export active PATH to new Node installation:
Mine direct path was /srv/baler/node-v10.14.1-linux-x64/bin but you can use pwd command to get real path and configure it.
To test once this is installed:
~/baler/bin$ ./baler --help Usage $ baler <command> [options] Commands build --theme Vendor/name graph --theme Vendor/name Examples Optimize all eligible themes $ baler build Optimize multiple themes $ baler build --theme Magento/foo --theme Magento/bar Generate Dependency Graph $ baler graph --theme Magento/luma
Next jump to the Magento 2 docroot and run it:
:~/public_html$ /srv/baler/bin/baler ✔ Collected theme/module data 155ms ✔ (Magento/luma) Created core bundle file 1.2s ✔ (Magento/luma) Minified core bundle and RequireJS 17.6s Optimization is done, but stats have not been implemented in the CLI yet
Clear Magento and Redis (if installed) cache:
~/public_html$ n98-magerun2 cache:clean config cache cleaned layout cache cleaned block_html cache cleaned collections cache cleaned reflection cache cleaned db_ddl cache cleaned compiled_config cache cleaned eav cache cleaned customer_notification cache cleaned config_integration cache cleaned config_integration_api cache cleaned google_product cache cleaned full_page cache cleaned config_webservice cache cleaned translate cache cleaned vertex cache cleaned
~/public_html$ n98-magerun2 cache:flush redis-cli flushconfig cache flushed layout cache flushed block_html cache flushed collections cache flushed reflection cache flushed db_ddl cache flushed compiled_config cache flushed eav cache flushed customer_notification cache flushed config_integration cache flushed config_integration_api cache flushed google_product cache flushed full_page cache flushed config_webservice cache flushed translate cache flushed vertex cache flushed
~/public_html$ redis-cli flushall OK
(this one is optional if Redis used)
Next, we need to install Magento 2 module which is going to handle bundlings:
composer config repositories.baler vcs https://github.com/adifucan/m2-baler
composer require magento/module-baler:dev-master
n98-magerun2 module:enable Magento_Baler
Run deployment process (setup:upgrade ; setup:di:compile and setup:static-content:deploy)
Clear Magento/Redis cache like we did it upper and then push the following:
php bin/magento config:set dev/js/enable_baler_js_bundling 1
Run the baler once again:
$ /srv/baler/bin/baler build ✔ Collected theme/module data 156ms ✔ (Magento/luma) Created core bundle file 1.2s ✔ (Magento/luma) Minified core bundle and RequireJS 17.8s Optimization is done, but stats have not been implemented in the CLI yet
php bin/magento config:set dev/js/minify_files 0
php bin/magento config:set dev/js/enable_js_bundling 0
php bin/magento config:set dev/js/merge_files 0
Clear Magento/Redis cache once again (yeah I know boring...), load frontpage and test...
While this is still in Alpha testing, there are certain things that needs to be patched. You can read them here https://github.com/DrewML/baler/issues/6
If you just want to apply the fixes, see the patch in core here https://github.com/magento/magento2/commit/db43c11c6830465b764ede32abb7262258e5f574
That's it! Most pages in your storefront should now be faster than they were before.