Managing gems has been painful lately. Like most people, we’re freezing them, which helps tremendously. However, there’s a few problems with this approach:

• We can’t freeze C extensions because they need to be compiled for the target platform. We develop on OS X and Linux 64, but deploy to Linux i386. As a workaround, we currently freeze but recompile them on every deployment. Definitely not optimal.
• Our frozen gems directory is getting huge.
• It’s becoming complicated and quite a mess to manage multiple gem versions for different branches/tags.
• We never quite know which branch needs which gem.

Of course, we could manually install the gems we need on our servers. But the word “manually” generally leads to “epic fail”.

So I thought, why not install them at deployment time, just before restarting the Mongrels, with Capistrano? That seemed like a pretty good idea! The only problem is that Rubygems will always install a gem when asked to do so, even if it’s already installed.

That’s where install_gems.rb comes in. install_gems.rb takes a file name as an argument. This file contains a simple list of gems along with their version number. A custom installation command can also be specified.

Here’s an example:

# This is an example file. As you can see, it supports comments.
haml 2.0.3
eventmachine 0.12.2
# Notice the custom command specified after the --
termios 0.9.4 -- gem install termios -v 0.9.4 --no-rdoc --no-ri

To install the above gems, you’d simply run
./install_gems.rb input_file

install_gems.rb has a few advantages over vanilla rubygems:

• It will only install a gem if the specified version is not already installed. That’s obviously much faster than reinstalling everything every time.
• C extensions will be properly compiled.
• Using different gem versions in different branches/tags/releases is now very easy. You just have to maintain a list of required gems in your Git repository and make sure Capistrano runs install_gems.rb against this list before restarting the application servers.
• It forces us to keep an up-to-date list of the gems we need.

Of course, for this to work as expected, you’ll need to require specific gem versions in your application. Your production server will likely have multiple versions of the same gems installed and if you don’t specify which version of the gem you want to require, things might (or will) break.

I released install_gems.rb on GitHub and Daniel Haran has already submitted a patch. Feel free to do so as well, I’m a puller!

Leopard’s Rails installation worked great until I updated Rubygems with sudo gem update –system. After I did that, most of my gems were broken, and reinstalling them didn’t help. According to Google, I was not alone.

The right thing to do for Apple would have been to ship Leopard with MacPorts and have Ruby and Rubygems installed through it. Unfortunately, they had to reinvent the wheel…

This tutorial will guide you through fixing that mess. We will be reinstalling Ruby and Rails with MacPorts and deleting the original Ruby installation to avoid conflicts.

You might want to backup your system before proceeding as I cannot be held responsible if something goes wrong (my lawyer made me write that). I tried it on 2 different machines and it worked fine for me.

So let’s get started already!

Step 1: Install MacPorts

Start by installing MacPorts if you don’t already have it on your machine. It’s an awesome must-have piece of software anyways! It’s super easy to install with the Leopard package.

Step 2: Install XCode 3.0

You must also have XCode 3.0 installed. It’s a huge download so you might want to install it from your Leopard DVD. It’s in /Optional Installs/Xcode Tools/XcodeTools.mpkg

Installation will take some time, so go read Digg, Reddit, or install Defensio on your blog!

Step 3: List your gems

Get a list of your installed gems and save it to a text file somewhere. You will need to reinstall them! [source:php]gem list > ~/Desktop/installed_gems.txt[/source]

Step 4: Clean up your Mac

In order to avoid conflicts with your original Ruby installation, I recommend you simply delete it. To do so, run these commands (I know… scary stuff!):[source:php]sudo rm -r /System/Library/Frameworks/Ruby.framework/
sudo rm -r /Library/Ruby
sudo rm /usr/bin/ruby
sudo rm /usr/bin/gem
[/source]

Step 5: Install Ruby and Rubygems with MacPorts

If you don’t perform step 4, you will run into problems at step 6.

Now go ahead and install Rubygems through MacPorts. It will automatically install Ruby (and many other things) as it’s a dependency. The command is: [source:php]sudo port install rb-rubygems[/source]

This one will also take a while… When it’s done, update Rubygems: [source:php]sudo gem update –system[/source]

Step 6: Install Rails

At this point, you should have a brand new Ruby and Rubygems installation working! That wasn’t too hard was it?

Now let’s install Rails.

• For Rails 1.2.6, run [source:php]sudo gem install rails -v 1.2.6[/source]
• For Rails 2 (aka latest-and-greatest), run [source:php]sudo gem install rails[/source]

Note that recent versions of Rubygems no longer requires the –include-dependencies parameter.

Step 7: Reinstall your gems

Now’s the time to reinstall your original gems.

To reinstall the gems that shipped with Leopard, execute this command: [source:php]sudo gem install RedCloth acts_as_ferret mongrel fcgi capistrano ruby-openid ferret dnssd hpricot sqlite3-ruby libxml-ruby termios[/source]

Then, you might want to reinstall the other gems you had. The list is on your desktop in installed_gems.txt.

That’s it! You now have a more standard and less prone to problems Rails stack on your Mac!