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Using rbenv to manage rubies

How I use rbenv to manage rubies and integrate with other tools

Estimated reading time: 4 minutes

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rbenv is great

If you haven’t seen rbenv yet I highly recommend it. It is a small collection of shell scripts that lets you manage rubies on UNIX type machines. To date I’ve used rvm to install versions of ruby and manage gemsets. Don’t get me wrong - I’m hugely greatful to the work that has gone into the rvm project and it is still a great tool. But I prefer the UNIX philosophy of doing one thing well and rbenv embraces that. I also really like that with rbenv you just need to amend your PATH and you are done. It follows UNIX conventions making integration with other UNIX tools easier - for me at least.

rbenv basics

We have a dev machine at work which runs a variety of Sinatra and Rails projects (including a Rails 1 project). As such these projects need lots of different versions of Ruby. To date I’ve used rvm to manage this and it has worked well but I always came up against issues when trying to integrate tools like Monit, puppet or init.d scripts. So I bit the bullet and switched to rbenv.

Each app has a UNIX user so rbenv is installed locally for each user when logged in as the user account

git clone git:// .rbenv

You need to load rbenv into the shell and you are good to go

echo 'export PATH="$HOME/.rbenv/bin:$PATH"' >> ~/.bashrc
echo 'eval "$(rbenv init -)"' >> ~/.bashrc
source ~/.bashrc

If you have installed ruby-build you can then install rubies with rbenv install.

rbenv install 1.9.3-rc1

You can set a global ruby for the user account with

rbenv global 1.9.3-rc1

And you can also use an .rbenv-version file to set the version. I choose to use this in projects and check it into git.

Deployment with capistrano

I like that rbenv doesn’t try and manage rubies for you - we have bundler for that. I deploy as the same user as the app accounts so I just need to add the following to my cap recipe to use rbenv since I’m already including require 'bundler/capistrano'.

set :default_environment, {
  'PATH' => "/home/youruser/.rbenv/shims:/home/youruser/.rbenv/bin:$PATH"

This loads rbenv into the shell that capistrano uses. That’s pretty much all you need to use your rbenv installed ruby.

Following a thread on github you can also apply a clever technique to allow you switch versions of ruby by pushing a new .rbenv-version file with capistrano. From version 1.1rc bundler allows you to specify a shebang for binstubs. To use this add the following to your capistrano recipe.

set :bundle_flags, "--deployment --quiet --binstubs --shebang ruby-local-exec"

This generates executables in the bin folder of your Rails app which reference ruby-local-exec as the shebang. This command will execute whichever ruby is specified in the .rbenv-version file. In my case I have an init.d script to manage unicorn that references bin/unicorn. If I wanted to upgrade the ruby used by the app I would install it on the remote machine and then just update my .rbenv-version file commit, cap deploy and I’m done.

Integrating with other tools

I like to use monit to monitor processes. Monit exexutes scripts with a very limited shell but since rbenv follows UNIX conventions we can easily create a small bash script to load rbenv into the path and then do what we want.

Here’s the script I’m using for starting a resque_worker

#!/usr/bin/env bash

RAILS_ENV=$RAILS_ENV bin/rake environment resque:work& > $APP_PATH/log/resque_worker.log 
echo $! > $APP_PATH/tmp/pids/

Then my monit task looks like this

check process yourapp_resque_worker
    with pidfile /srv/
    start program = "/bin/sh -c '/home/youruser/bin/'" as uid youruser and gid youruser
    stop program = "/bin/sh -c 'cd /srv/ && kill -s quit `cat tmp/pids/` && rm -f tmp/pids/; exit 0;'"

Better separation

By using rbenv, bundler, capistrano and monit together we have great separation between what these tools do

This feels clean and manageable to me.

By using binstubs with the ruby-local-exec shebang we also separate our app from versions of rubies, init.d and monit scripts, making it super easy to upgrade.

Thanks rvm, onwards with rbenv

I’m really grateful to Wayne E Seguin and the work he has put into rvm and I hope the project continues to thrive. rbenv fits the way I work though and I’m really enjoying using it. It makes piecing tools like puppet, monit, init.d scripts, capistrano and bundler much easier, so a big thanks to Sam Stephenson for creating it.

Have an update or suggestion for this article? You can edit it here and send me a pull request.


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