rebund

Makes your CI build much faster by caching your bundle.

Rationale

Running bundle install to get all gems ready is often the longest part of a build. Any Rails application will depend on tens of gems; and any gem, besides dependencies, may have a fairly large build matrix.

Rebund can easily cut your build times by 75%, saving you time and saving the good folks at Travis CI some money.

Example for an application, appfab.io (5.3x speedup):

Example for a gem, fuzzily (2.7x speedup):

Rebund is an alernative to bundle_cache, which didn't work well enough for us on Travis because it relies on gems to be installed (which partly defeats the purpose).

How it works

Before your build, Rebund checks with a file server if there's a bundle already available for your current Ruby VM and version of the Gemfile.lock. Technically, it hashes the output of ruby --version and the lockfile.

If there is one, it downloads and unpacks it, then making bundle install blazing fast.

After the build, Rebund packages the bundle (if changed) and uploads it for future uses.

Prerequisites

Rebund needs an HTTP endpoint to store and retrieve bundle files. It's tested with keyfile, a no-frills alternative to S3 with more standard authentication, and defaults to the version I host.

If you don't have credentials to use that Keyfile server, you can

• deploy your own (read the docs)
• ask me for credentials on my hosted version.

Installation

Add rebund to your repository as a submodule:

$ git submodule add https://github.com/mezis/rebund.git

While submodules are not necessarily a great idea in general, we can't rely on Rubygems to install rebund as it needs to run before running Bundler.

The next step is to instruct Travis to attempt to use a cached bundle before the build, and upload a bundle if needed after the build. Add the following lines to your .travis.yml config file.

install:
  - ./rebund/run download
  - bundle install --path vendor/bundle
after_script:
  - ./rebund/run upload

(Optional) if you're using your own Keyfile server, specify it in your Travis config:

env:
  global:
    - REBUND_ENDPOINT=http://my-rebund.io

Finally, add your rebund cretentials to the configuration:

$ travis encrypt REBUND_CREDENTIALS=username:secret --add    

Push your changes, and watch the build work. Of course you'll only get the benefits from the second build onwards!

Caveats

Gemfiles in subdirectories

Rebund assumes that your bundle goes to vendor/bundle, relative to the root of your project. In some cases (e.g. when using Appraisal), the Gemfile resides in a subdirectory.

Given the --path option to bundle install is relative to the Gemfile, you will need to change the Travis configuration to

bundle install --path vendor/bundle

License

Released under the MIT licence. Copyright (c) 2014 HouseTrip Ltd.

Contributing

1. Fork it
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create a new Pull Request