Musings of a Trained Monkey

Let's get the tarball for RubyGems 0.9.0 and explode it in the home directory on our shared host:

curl -o rubygems-0.9.0.tgz http://rubyforge.rubyuser.de/rubygems/rubygems-0.9.0.tgz
tar xzvf rubygems-0.9.0.tgz
cd rubygems-0.9.0

The tgz distribution can also be found at RubyForge if you don't have curl. Now we need to patch the file ~/rubygems-0.9.0/lib/rubygems/custom_require.rb inside of the RubyGems distribution to make Gem::GemPathSearcher a Singleton. This is chronicled both on this blog and in the still unloved RubyGems patch 5394, reproduced here for ease of cut and paste, minus all comment lines:

require 'rubygems/source_index'
require 'singleton'

module Kernel
  alias gem_original_require require
  def require(path)
    gem_original_require path
  rescue LoadError => load_error
    begin
      @gempath_searcher = Gem::GemPathSearcher.instance
      if spec = @gempath_searcher.find(path)
        Gem.activate(spec.name, false, "= #{spec.version}")
        gem_original_require path
      else
        raise load_error
      end
    end
  end
end

module Gem
  class GemPathSearcher
    include Singleton
...

After making this change it is time to install, since we are installing as non-root we have to make a couple of changes to the standard procedure. Let's go ahead and plan on installing to a directory in the home directory named "myrubygems". Also we will need to specify a GEM_HOME for our local repository (using "/gems" where <HOME> is the full path to your home folder) and we will specify the GEM_PATH to point to the shared hosts gem repository. To find where your shared host keeps its gem repository run the command gem environment. TextDrive has it installed in the same place as Ruby which will create a little wrinkle for us later.

export GEM_HOME=<HOME>/gems
export GEM_PATH=/usr/local/lib/ruby/gems/1.8/

ruby setup.rb config --prefix=<HOME>/myrubygems
ruby setup.rb setup
ruby setup.rb install

You'll need to modify your $PATH variable to include the patched version of RubyGems first in the list. Here is the line from my .bash_profile file:

export PATH=$HOME/myrubygems/bin:$PATH

Make sure you add this to your $PATH permanently or when your app restarts it will not use the patched version. At this point we can see how we are doing by typing the command which gem it should list the path to the patched version of RubyGems. If not recheck the previous steps.

Two files left to edit, ~/myrubygems/bin/gem and the RAILS_ROOT/public/dispatch.fcgi. RAILS_ROOT is the path to the rails app you want to pick up the patched RubyGems. Both need the shebang line at the top changed to:

#!/usr/local/bin/ruby -I<HOME>/myrubygems/lib/ruby/site_ruby/1.8/
#Again <HOME> needs to be the fully expanded version here for this to work

This is the wrinkle I mentioned earlier. The shebang change is necessary due to the shared host gem repository being installed in the same place as Ruby. The -I option specifies that our patched version of RubyGems be included in the $LOAD_PATH before even Ruby is loaded. I will have more to say about $LOAD_PATH in an upcoming post.