Parallel Ruby Gem installation using Bundler 1.5.2
Change effective on 16 January 2014
Bundler version 1.5.2 allows gems to be installed in parallel. This version also includes a critical fix for a parallel gem installation problem present in 1.5.1. The Ruby buildpack now uses Bundler 1.5.2 and installs using 4 parallel processes using the flag -j4.
Installing Ruby Gems can take a long amount of time due to the number of network requests that are required. By making these requests in parallel we can better utilize the resources available and greatly speed up deploy time.
In your Ruby deploy output you should now see the flag -j4
Running: bundle install --without development:test --path vendor/bundle --binstubs vendor/bundle/bin -j4 --deployment
Previously version 1.5.1 of Bundler was deployed on Heroku but had to be reverted due to a problem installing self referential gems. This issue has been fixed in Bundler is in 1.5.2.