Ruby application server

Ruby application web server

Ruby contains a default application web server named WEBrick. As it is always present, most web framework use it by default. It’s good enough in development, but it has never been thought to be a production server.

Do not use WEBrick

WEBrick has the following caracteristics:

  • Single threaded
  • Single process

It can’t handle several request in parallel, they are all in a single request queue. As a result, very pool performance can be expected. To get the best of your containers, you need to use a real production-ready application server.

Using Puma as a production server

To handle several requests in parallel, we recommend puma. To use it, just add it as dependency in your Gemfile:

gem 'puma'

and configure how to launch your app by defining a Procfile:

web: bundle exec puma -C config/puma.rb

The config file could like the following:

workers Integer(ENV['WEB_CONCURRENCY'] || 2)
threads_count = Integer(ENV['MAX_THREADS'] || 5)
threads threads_count, threads_count


rackup      DefaultRackup
port        ENV['PORT']     || 3000
environment ENV['RACK_ENV'] || 'development'

on_worker_boot do
  # Worker specific setup for Rails 4.1+

Thus you can easily change global settings by modifying the environment variables WEB_CONCURRENCY and MAX_THREAD and restarting your app.

schedule 21 Mar 2016