Ruby 2.0 Preview Available on Heroku

When Heroku first launched you could only use one version of Ruby: 1.8.6. As the Ruby implementation matured and improved, so did Heroku. We recently announced the ability to specify your ruby version on Heroku, and we are happy to announce the first preview-build of Ruby available: starting today you can use Ruby 2.0 preview1 on Heroku.

Ruby 2.0

The Ruby core team has been hard at work on Ruby 2.0, which has a host of new features and boasts performance improvements. You can get a list of the major new features on the official Ruby 2.0.0 Preview1 announcement.

Heroku has been committed to the Ruby project by sponsoring the work of Yukihiro "Matz" Matsumoto, Koichi Sasada and Nobuyoshi Nakada on MRI Ruby. We have been very pleased with Ruby Core's progress, and look forward to the full release. You can take an in-depth look at the new Ruby 2.0 features available. But don't just read about it, try it out on Heroku today:

Get Ruby 2.0 Running on Heroku

Start by making a Gemfile that specifies Ruby 2.0.0:

$ echo 'source ""'  > Gemfile
$ bundle install
$ echo 'ruby "2.0.0"' >> Gemfile

Add the files to a Git repository:

$ git init
$ git add .
$ git commit -m "Ruby 2.0.0 preview on Heroku"

Then create a new heroku app and deploy:

$ heroku create
$ git push heroku master
-----> Heroku receiving push
-----> Ruby app detected
-----> Using Ruby version: ruby-2.0.0
-----> Installing dependencies using Bundler version 1.2.1
       Running: bundle install --without development:test --path vendor/bundle --binstubs bin/ --deployment
       The Gemfile specifies no dependencies
       Your bundle is complete! It was installed into ./vendor/bundle
       Cleaning up the bundler cache.
-----> Discovering process types
       Procfile declares types -> (none)
       Default types for Ruby  -> console, rake
-----> Compiled slug size: 23.3MB
-----> Launching... done, v4 deployed to Heroku

 * [new branch]      master -> master

Now you can run Ruby 2.0 beta on Heroku!

$ heroku run bash
Running `bash` attached to terminal... up, run.1
~ $ ruby --version
ruby 2.0.0dev (2012-11-01 trunk 37411) [x86_64-linux]
~ $ ruby -e "puts 'hello world'"
hello world

Why Run 2.0 Preview1?

Ruby 2.0 will ship on February 24th, 2013 - which is four days before our developer conference Waza. Heroku's own Matz has announced that Rails 3.2 apps should work with Ruby 2.0 if they work on Ruby 1.9. Help us find any incompatibilities by checking your existing applications on Heroku. If you run into any bugs in the Ruby implementation, please open a bug in the Ruby bug tracker and let the Ruby team know what didn't work with the implementation.


If you are updating an existing app you will likely need to update your config vars manually. New apps should not experience any problems.


Thanks to the entire Ruby Core Team for their hard work on this release of Ruby, and special thanks to Terence Lee. Terence is Heroku's Ruby buildpack maintainer who did the leg work to enable Ruby 2.0.0 Preview1 on Heroku. Please try out this Ruby preview today, to help the Ruby core team and to help our community. Try it today.

Multiple Ruby Version Support on Heroku

Maximizing parity between development and production environments is a best practice for minimizing surprises at deployment time. The version of language VM you're using is no exception. One approach to this is to specify it using the same dependency management tool used to specify the versions of libraries your app uses. Clojure uses this technique with Leinigen, Scala with SBT, and Node.js with NPM. In each case, Heroku reads the dependency file during slug compile and uses the version of the language that you specify.

Today, we're pleased to announce that we've added support for specifying a Ruby version to Gem Bundler, the dependency management tool for Ruby. This will allow you to specify a version of Ruby to be used in your Ruby app on Heroku.

Try it out:

$ gem install bundler --pre

In your Gemfile:

source ''

ruby '1.9.3'
gem  'rails', '3.2.3'


$ bundle install
$ git add Gemfile
$ git commit -m 'use Ruby 1.9.3'
$ git push heroku master

Prove that you're running 1.9.3:

$ heroku run 'ruby -v'
ruby 1.9.3p194 (2012-04-20 revision 35410) [x86_64-linux]

$ heroku run 'ruby -e "puts RUBY_VERSION"'

Patch Versions

While you can specify the version of Ruby for you app, you can't specify a patch version, such as Ruby 1.9.2-p290. Ruby patches often include important bug and security fixes and are extremely compatible. Heroku will provide the most secure patch level of whatever minor version number you request.


Thanks to Terence Lee Heroku Ruby team member and bundler maintainer for the additional support of ruby versions to the Heroku Ruby Buildpack and orchestrated the release of Bundler 1.2.0. Also thanks to Yehuda Katz and the entire Bundler team for helping get this release out the door.

Matz Named 2011 Free Software Award Winner

We are pleased to announce that Yukihiro "Matz" Matsumoto, the creator of Ruby and Heroku's Chief Ruby Architect, has received the 2011 annual Advancement of Free Software Award. Presented by Richard Stallman and on behalf of the Free Software Foundation, the award is given each year to those who have greatly contributed to the freedom of software.

This is great news for Matz, who has dedicated over 20 years to the development of free software including the creation of the Ruby programming language. While writing Ruby he chose to focus on programmer happiness and productivity, and the result has been extraordinary. The popularity of the language, helped in part by the Rails framework, has encouraged a new generation of free software advocates who together have released more than 36,000 freely downloadable Ruby libraries known as Gems.

This award is also a huge win for Ruby. It's a recognition of Ruby's importance, will bring more people into the community, and encourages more developers to share their work. If you'd like to contribute to Ruby, visit the ruby core page where you can learn how to submit a patch or file a bug report.

We're very proud of the Ruby community as a whole, and for Matz and all of his accomplishments. So please join us today, along with the Free Software Foundation, in thanking him for all of his hard work.

Defaulting to Ruby 1.9.2

Heroku is fully behind Ruby 1.9.2 as the new gold standard for production Ruby apps. Over the past few months, we’ve seen more and more developers move to the Bamboo 1.9.2 stack. It’s fast, stable, and increasingly sees excellent support throughout the community.

In February, we said that we’d be reviewing the state of 1.9.2 support with the eventual goal of switching the default for new Ruby apps on Heroku from 1.8.7 to 1.9.2. Today, we’re announcing the date of that switchover.

As of June 1st, 2011, all new Ruby applications on Heroku will be run on Ruby 1.9.2 by default. (Existing applications won’t be affected, and you can always create a new application on 1.8.7 by running heroku create --stack bamboo-ree-1.8.7.)

But there’s no need to wait till June – get started with a Ruby 1.9.2 app on Heroku today with the following command:

$ heroku create --stack bamboo-mri-1.9.2

The Path Forward: Ruby 1.9.2

At Heroku, we’ve been watching the progress of MRI very carefully for a while now; we added support for 1.9.1 nearly a year ago and 1.9.2 more recently, and we’ve seen thousands of apps created and running successfully on the 1.9 series of VMs. At the same time, we’ve seen the community as a whole recognize the importance of 1.9 by migrating libraries and gems to it and providing resources and tutorials on upgrading.

Today, Heroku is putting our full support behind Ruby 1.9.2 as the future of MRI. It is a stable, battle-tested, production-quality Ruby, and we’re excited to see it become the mainstay for future Ruby development.

What this means today

We encourage all Heroku developers to use Ruby 1.9.2 for new apps. You can create an app on 1.9.2 with the following command:

$ heroku create --stack bamboo-mri-1.9.2

We also encourage developers to port (or at least test) existing apps on 1.9.2, and to contribute bug reports, feedback, and patches to libraries that aren’t currently 1.9.2-compatible:

$ heroku stack:migrate bamboo-mri-1.9.2

As part of this effort, we have also deprecated the bamboo-mri-1.9.1 stack. Apps that are currently running on it will not be affected, but no new 1.9.1 apps can be created, and you are no longer able to migrate to 1.9.1.

What this means going forward

As of now, bamboo-ree-1.8.7 is still the default stack for new Heroku apps. As support for Ruby 1.9.2 continues to improve, we will regularly review this, with the goal of making 1.9.2 the default in the future. We’ll provide plenty of notice before this switch, of course.

Resources for Ruby 1.9.2

There are a number of great resources for learning about and trying out Ruby 1.9.2. Here are some of our favorites, but feel free to leave yours in the comments!

  • Programming Ruby 1.9 – the latest edition of the book that brought Ruby to the English-speaking world.
  • RVM – we recommend RVM for managing your Rubies in development; it makes testing apps against alternate implementations as painless as possible.
  • Upgrading to Ruby 1.9 – David A Black’s summary of the top 10 things to watch out for when moving from 1.8 to 1.9 – and don’t miss the sequel, which contains even more good information.
  • Is It Ruby 1.9? – a community-powered site for monitoring gem compatibility (and be sure to contribute to it!)

Browse the blog archives or subscribe to the full-text feed.

Visit the Engineering Blog