问题
Do Heroku Cedar stack apps require thin and eventmachine in Gemfile?
gem 'thin'
gem 'eventmahine'
What about versions? On other stacks they were installed automatically?
回答1:
Yes, you need to specify any gem that you want to use on Cedar stack unlike on Bamboo which had preinstalled gems.
Go with whatever version your application needs,
来源：https://stackoverflow.com/questions/8362303/heroku-cedar-stack-thin-and-eventmachine