A large amount of time of a normal build is spent installing dependencies, be it Ubuntu packages or simply running bundle install or npm install on a normal project. On an average Rails project, this can take a few minutes to succeed unfortunately.

This is dreadful to watch and it takes precious time that should rather be spent running the build. We’ve seen some great initiatives from customers to cache bundles, like bundle_cache (inspired by our friends at Kisko Labs) and WAD from the fine folks at Fingertips.

But in the end, it became clear that we need to offer something that’s built-in, automatically caching our customers’ bundles without requiring major changes to their build configuration.

Today, we’re officially announcing built-in caching for dependencies.

While it integrates nicely with Bundler already, you can also use it to cache Node packages, Composer directories, or Python PIP installations. Heck, you can even use it to speed up the asset pipeline’s temporary test cache, to speed up builds even more.

Plus, caching an entire bundle of dependencies has the benefit of reducing the impact of outages of dependency mirrors.

To give you an idea of the impact of this simple yet efficient way of speeding up builds, we’ve had customers report saving a total of half an hour or more on their builds with bigger build matrixes.

On our billing app, it shaved off four minutes, cutting the build time down to one minute.

How can you enable it for your private projects?

If you’d like us to cache your Bundler directory, simply add the following to your .travis.yml:

cache: bundler

If you want to add the asset pipeline’s compilation cache, you can specify the directories to cache as well:

cache:
  bundler: true
  directories:
    - tmp/cache/assets/test/sprockets

For a Node.js project, simply specify the node_modules directory:

cache:
  directories:
    - node_modules

The specified paths are relative to the build directory.

Cache Rules Everything Around Me

We’re working on getting more language-specific caching methods included, and on getting common dependency mirrors closer to our infrastructure, as we already did with a network-local APT cache.

Bundler 1.5 has great features upcoming, including Gem Source Mirrors, which we’re looking into utilizing to increase the reliability of installing RubyGems.

Stay tuned, and happy caching!

For all the gory details on caching, see our docs. Note that this feature is currently only available for private repositories.

The tool we’re using to cache dependencies is open source!