tl;dr: Run composer require zaporylie/composer-drupal-optimizations:^1.0 in your Drupal codebase to halve Composer's RAM usage and make operations like require and update 3-4x faster.

A few weeks ago, I noticed Drupal VM's PHP 5.6 automated test suite started failing on the step that runs composer require drupal/drush . (PSA: PHP 5.6 is officially dead. Don't use it anymore. If you're still using it, upgrade to a supported version ASAP!). This was the error message I was getting from Travis CI:

PHP Fatal error: Allowed memory size of 2147483648 bytes exhausted (tried to allocate 32 bytes) in phar:///usr/bin/composer/src/Composer/DependencyResolver/RuleWatchNode.php on line 40

I ran the test suite locally, and didn't have the same issue (locally I have PHP's CLI memory limit set to -1 so it never runs out of RAM unless I do insane-crazy things.

So then I ran the same test but with PHP's memory_limit set to 2G —yeah, that's two gigabytes of RAM—and it failed! So I ran the command again using Composer's --profile option and -vv to see exactly what was happening:

# Run PHP 5.6 in a container.

$ docker run --rm -it drupaldocker/php-dev:5.6-cli /bin/bash

# php -v

PHP 5.6.36 (cli) (built: Jun 20 2018 23:33:51)



# composer create-project drupal-composer/drupal-project:8.x-dev composer-test --prefer-dist --no-interaction



# Install Devel module.

# cd composer-test

# composer require drupal/devel:^1.2 -vv --profile

Do not run Composer as root/super user! See https://getcomposer.org/root for details

[126.7MB/5.04s] ./composer.json has been updated

[129.6MB/6.08s] > pre-update-cmd: DrupalProject\composer\ScriptHandler::checkComposerVersion

[131.5MB/6.10s] Loading composer repositories with package information

[131.9MB/6.52s] Updating dependencies (including require-dev)

[2054.4MB/58.32s] Dependency resolution completed in 3.713 seconds

[2054.9MB/61.89s] Analyzed 18867 packages to resolve dependencies

[2054.9MB/61.89s] Analyzed 1577311 rules to resolve dependencies

[2056.9MB/62.68s] Dependency resolution completed in 0.002 seconds

[2055.5MB/62.69s] Package operations: 1 install, 0 updates, 0 removals

[2055.5MB/62.69s] Installs: drupal/devel:1.2.0

[2055.5MB/62.70s] Patching is disabled. Skipping.

[2055.5MB/62.80s] - Installing drupal/devel (1.2.0): [2055.6MB/62.83s] [2055.6MB/63.02s] Downloading (0%)[2055.6MB/63.02s] [2[2055.6MB/63.04s] Downloading (5%)[2[2055.6MB/63.06s] Downloading (15%)[[2055.7MB/63.08s] Downloading (30%)[[2055.7MB/63.10s] Downloading (40%)[[2055.8MB/63.12s] Downloading (55%)[[2055.8MB/63.14s] Downloading (65%)[[2055.9MB/63.15s] Downloading (75%)[[2055.9MB/63.15s] Downloading (80%)[[2055.9MB/63.17s] Downloading (90%)[[2056.0MB/63.18s] Downloading (100%)[2055.5MB/63.19s]

[2055.5MB/63.19s] Extracting archive[2055.6MB/63.57s] REASON: Required by the root package: Install command rule (install drupal/devel 1.x-dev|install drupal/devel 1.2.0)

[2055.6MB/63.57s]

[2055.6MB/63.57s] No patches found for drupal/devel.

[731.5MB/71.30s] Writing lock file

[731.5MB/71.30s] Generating autoload files

[731.8MB/73.01s] > post-update-cmd: DrupalProject\composer\ScriptHandler::createRequiredFiles

[731.6MB/78.82s] Memory usage: 731.61MB (peak: 2057.24MB), time: 78.82s

So... when it started looking through Drupal's full stack of dependencies—some 18,867 packages and 1,577,311 rules—it gobbled up over 2 GB of RAM. No wonder it failed when memory_limit was 2G !

That seems pretty insane, so I started digging a bit more, and found that the PHP 7.1 and 7.2 builds were not failing; they peaked around 1.2 GB of RAM usage (yet another reason you should be running PHP 7.x—it uses way less RAM for so many different operations!).

Then I found a really neat package which had some outlandish promises: composer-drupal-optimizations mentioned in the README:

Before: 876 MB RAM, 17s; After: 250 MB RAM, 5s

I went ahead and added the package to a fresh new Drupal project with:

composer require zaporylie/composer-drupal-optimizations:^1.0

(Note that this operations still uses the same huge amount of memory and time, because the package to optimize things is being installed!)

And then I ran all the tests on PHP 5.6, 7.1, and 7.2 again. Instead of spelling out the gory details (they're all documented in this issue in the Drupal VM issue queue), here is a table of the amazing results:

PHP Version Before After Difference 5.6 2057.24 MB 540.02 MB -1.5 GB 7.1 1124.52 MB 426.64 MB -800 MB 7.2 1190.94 MB 423.93 MB -767 MB

You don't have to be on ancient-and-unsupported PHP 5.6 to benefit from the speedup afforded by ignoring unused/really old Symfony packages!

Next Steps

You should immediately add this package to your Drupal site (if you're using Composer to manage it) if you run Drupal 8.5 or later. And if you use a newer version of Acquia BLT, you're already covered! I'm hoping this package will be added upstream to drupal-project as well (there's sort-of an issue for that), and maybe even something could be done on the Drupal level.