Ruby Gems, the Bundler, and Deploying a Jar File
We ran intro a very interesting problem today with Warbler, Bundler and a bug in Hamster. To set the stage, Bundler is able to have gems specified as git/GitHub resources with the simple Gemfile line:
gem "Hamster",
:git => "git://github.com/harukizaemon/hamster.git"
and you can even specify a SHA for the commit point you want. Very nice.
The problem is that when you do this, Bundler places the resulting Gem into a Bundler/gems/ subdirectory of your current /gems/ directory, and that makes finding it impossible for the standard gem tools - which includes ruby itself.
What you must do is to let Bundler "fix" the GEM_PATH as soon as possible in your app. Simply require it's setup code and you are good to go:
require 'bundler/setup' # use Hamster as normal
This is OK, if you're going to include Bundler in your deployment package and you aren't using Warbler to place everything into a Jar for Java to execute. Then we get into some nasty problems.
Our situation is that we want to deploy a single jar file. This means using Warbler to jar things up easily. Again, this doesn't sound so bad, but it's this patching issue that Bundler uses that makes things very difficult - certainly when dealing with a jar. You see, Bundler doesn't "do jars" at all. It's looking for a file system to work on, so when you try to do the same thing within a jar, you get error messages on trying to change directories, etc. It's trying to move around the file system, but a jar isn't a file system, and JRuby doesn't make it any easier, so Bundler fails.
Warbler doesn't help here because it's a problem with JRuby and Bundler and the jar.
Our solution was to build the gem from the fixes and place is in a local gem server and then reference it in the Gemfile without using the git/GitHub scheme. This places the gem in the right directory, and that means we don't need Bundler to augment the GEM_PATH and that means it all works.
I'm convinced that the real solution is to fix/patch JRuby to allow all ruby-based file and directory operations to operate on a jar. However, that's probably not the typical deployment scheme as we really hardly ever leave a WAR file unexploded, and deploying Jars is pretty limited.
Lesson: Don't use Git Gems with Bundler if you're deploying to a Jar. It's just not going to work.