Deploying a Ruby app on a Heroku production server
with Passenger in Standalone mode

Add "passenger" to your gem bundle

Open your Gemfile. Remove lines that look like one of these:

gem "unicorn"
gem "thin"
gem "puma"

Make sure the following line exists:

gem "passenger"

When you are done, install your gem bundle with:

$ bundle install

Updating your Procfile

Open your app's Procfile, or create one if you don't already have one. Remove lines that look like one of these:

web: bundle exec ruby web.rb -p $PORT
web: bundle exec unicorn -p $PORT
web: bundle exec puma -p $PORT
web: bundle exec thin start -p $PORT

Insert:

web: bundle exec passenger start -p $PORT --max-pool-size 3

Pushing the code to Heroku

Commit and deploy to Heroku:

$ git commit -a -m "Switch to Passenger"
$ git push heroku master

Next step

Congratulations, you have now deployed your app with Passenger to Heroku!