Error Pushing to Heroku Caused By ZXing / FFI / Spoon Gem - ruby-on-rails

Question

I'm currently working on a project that requires the ZXing gem (http://rubydoc.info/gems/zxing/0.3.1/frames) for decoding images of barcodes. In my attempts to install the gem locally, I ran into some complications with dependencies, but those were resolved by adding the ffi (http://rubygems.org/gems/ffi) and spoon (http://rubygems.org/gems/spoon) gems to my Gemfile, in addition to jruby-jars. Now, everything is working fine on my local machines (an iMac and a MacBook Pro, both running Lion). However, when I try to push the application to Heroku, the terminal hangs on the following line for several minutes:
-----> Writing config/database.yml to read from DATABASE_URL
Then finally gives me the error message:
/app/slug-compiler/lib/utils.rb:62:in `block (2 levels) in spawn': command='/app/slug-compiler/lib/../buildpacks/ruby/bin/compile /tmp/build_31wo219fllz4d /app/tmp/repo.git/.cache' exit_status=0 out='' event=timeout elapsed=581.3388702869415 (Utils::TimeoutError)
from /app/slug-compiler/lib/utils.rb:48:in `loop'
from /app/slug-compiler/lib/utils.rb:48:in `block in spawn'
from /app/slug-compiler/lib/utils.rb:44:in `popen'
from /app/slug-compiler/lib/utils.rb:44:in `spawn'
from /app/slug-compiler/lib/buildpack.rb:35:in `block in compile'
from /app/slug-compiler/lib/buildpack.rb:33:in `fork'
from /app/slug-compiler/lib/buildpack.rb:33:in `compile'
from /app/slug-compiler/lib/slug.rb:464:in `block in run_buildpack'
from /app/slug-compiler/lib/utils.rb:117:in `log'
from /app/slug-compiler/lib/slug.rb:702:in `log'
from /app/slug-compiler/lib/slug.rb:463:in `run_buildpack'
from /app/slug-compiler/lib/slug.rb:107:in `block (2 levels) in compile'
from /app/slug-compiler/lib/utils.rb:98:in `block in timeout'
from /usr/local/lib/ruby/1.9.1/timeout.rb:58:in `timeout'
from /app/slug-compiler/lib/utils.rb:98:in `rescue in timeout'
from /app/slug-compiler/lib/utils.rb:93:in `timeout'
from /app/slug-compiler/lib/slug.rb:96:in `block in compile'
from /app/slug-compiler/lib/utils.rb:117:in `log'
from /app/slug-compiler/lib/slug.rb:702:in `log'
from /app/slug-compiler/lib/slug.rb:95:in `compile'
from /app/slug-compiler/bin/slugc:85:in `block in <main>'
from /app/slug-compiler/lib/slug.rb:472:in `block in lock'
from /app/slug-compiler/lib/repo_lock.rb:44:in `call'
from /app/slug-compiler/lib/repo_lock.rb:44:in `run'
from /app/slug-compiler/lib/slug.rb:472:in `lock'
from /app/slug-compiler/bin/slugc:66:in `<main>'
! Heroku push rejected, failed to compile Ruby/rails app
To git#heroku.application-testing-account:integrating-zxing-on-heroku.git
! [remote rejected] master -> master (pre-receive hook declined)
error: failed to push some refs to 'git#heroku.application-testing-account:integrating-zxing-on-heroku.git'
The problem seems to be caused by the ZXing gem and/or its dependencies (ffi, spoon). If I remove zxing from my Gemfile, Heroku compiles the application and everything works fine. Upon re-adding the gem, I experience the same problems. I've also tried setting config.assets.initialize_on_precompile to both true and false in my application.rb, but to no avail. I'm kind of stumped as to what to do now.
My application is on the Cedar stack and using PostgreSQL in development and production.
Could anyone offer any suggestions?

Answer 1

Yeah, unfortunately you can't use anything with C++ or Java dependencies. I'm having trouble finding a QR decoder that's pure ruby (and works well).