Bundler Tips

At Engine Yard, we advocate for the use of Bundler in users’ applications, mainly because it makes dependency management very easy. Avrohom Katz wrote a post with pro tips for Bundler and Evan Machnic wrote a post about some issues with Bundler and Rails 3.1. Still, there are some tips for using Bundler that will make deployment much easier.

Bundle your Bundler

As discussed in Evan’s post, specifying a version of Bundler in your Gemfile solves an issue described at Bundler Gemfile Version.

1. Specify the version in your Gemfile:

   gem ‘bundler’, ‘~> 1.15’

2. Update the Gemfile.lock from your development machine terminal:

    bundle update bundler

Use Bundle exec

Bundler keeps all of the gems that you have specified in its own kind of environment. To make sure you’re using only the specified gems, you can use the command bundle exec

Below are a couple of commands that take advantage of bundle exec

• Migrate the database using the specified Rake version

   bundle exec rake db:migrate

• Check the versions of gems that Bundler is using for your application

   bundle exec gem list

Use Binstubs

Engine Yard automatically installs binstubs in your application. This basically gives you the same abilities as bundle exec without having to call that command everytime. If for some reason the binstubs aren’t installed, you can install them with bundle install --binstubs

• bundle exec <executable> is the same as bin/<executable>

Bundle update

A note on using bundle update: it is usually only advisable to update a specific gem and not every gem. Using bundle update <gem> updates that gem and it’s dependencies and gives you warnings if that update will break your other dependencies. If you just run bundle update, that will update all the specified gems but there is more risk of breaking dependencies.

Pack your gems

Sometimes, you want to keep your gems with your application so that you don’t have to call out to rubygems.org to install the gems. This is where bundle pack comes in handy. Run that command from your development machine which will pack the gems into vendor/cache. When you deploy, run bundle install --local to install the gems from the vendor/cache directory.

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