Jetty Rails

→ ‘jetty-rails’


See the what is included in the last version.

Jetty Rails aims to run Ruby on Rails and Merb applications with the Jetty Container, leveraging the power of JRuby and jruby-rack.

Jetty is an excellent Java Web Server, being and at the same time extremely lightweight. This makes jetty-rails a good alternative for JRuby on Rails or Merb development and deployment.

The project has born from my own needs (read more). I needed to run JForum on the same context of my jruby on rails application. I had also to integrate HttpSessions (avoiding single sign on) and use ServletContext in-memory cache store.


jruby -S gem install jetty-rails

The basics

Jetty Rails uses Jetty Handlers to dispatch requests to the JRuby Rack adapter.

All extra jars inside your application lib/ dir will be loaded. Things like Java HttpSession, ServletContext and Runtime Pools are given by JRuby Rack Filter.

Additionally, Jetty Rails automatically puts classes inside the classes/ dir
in the application classpath, so you can use them in your rails code.

Demonstration of usage


cd myrailsapp
jruby -S jetty_rails


cd mymerbapp
jruby -S jetty_merb

—help option shows usage details:

jruby -S jetty_rails --help
jruby -S jetty_merb --help

Please note that you may only use Merb with ActiveRecord, as DataMapper doesn’t work in JRuby yet.

Multiple Servers

You can specify a configuration yaml file rather than command line switches.
The file also allows specifying multiple servers and / or application contexts for single jetty container. Jetty Documentation

For example, you could set a context_path of /testA on port 8888 which is rails, /testB also that port which is merb.
Or, you could have /testA on port 8888 and /testB on port 9999.

jruby -S jetty_rails -c path/to/config.yml 

The configuration options are inherited, so if you specify the environment to be “production” at the top level,
then any servers and application context will be “production” unless the choose to override the value.

- server settings:


- application context settings:


As part of the configuration you have some control over jruby & jetty. Take a look at one complete config.yml from the examples bundled in jetty-rails:

  - :context_path: /testA
    :base: jetty_rails_proj_2
    :adapter: :rails
    :environment: development
    :port: 2000
  - :context_path: /testB
    :adapter: :rails
    :base: jetty_rails_proj
    :environment: production
    :port: 3000
  - :port: 4000
    - :context_path: /testB
      :adapter: :rails
      :base: jetty_rails_proj
      :environment: development
    - :context_path: /testA
      :adapter: :rails
      :base: jetty_rails_proj_2
      :environment: production
  :environment: production
  :jruby_min_runtimes: 1
  :jruby_max_runtimes: 2
  :thread_pool_max: 40
  :thread_pool_min: 1
  :acceptor_size: 20

For more examples see:


If -c is not specified, by default jetty_rails will look for a config/jetty_rails.yml relative to where it is started.

Don’t forget to add this into your config/environment.rb

ActionController::AbstractRequest.relative_url_root = “/testA”

JRuby Configuration

You can tweak the JRuby runtimes per application context:

:jruby_min_runtimes: 1
:jruby_max_runtimes: 2

Jetty Configuration

You can also modify the jetty per server configurations.

Thread pool will define the thread pool available to the jetty server using a QueuedThreadPool.

:thread_pool_max: 40
:thread_pool_min: 1

The acceptor size is the number of acceptor threads available for that server’s channel connector.

:acceptor_size: 20

See the jetty documentation for more information.

More Documentation

See RDoc

Mailing list

Bug Tracking and New Features

Using Lighthouse:

Getting the source


git clone git://

Build and test instructions

cd jetty-rails
jruby -S rake # run specs
jruby -S rake package
jruby -S gem install pkg/*.gem


Jetty Rails is distributed under the terms of The MIT License.

Copyright © 2008 Fabio Kung

Read more details in the bundled Licenses.txt file. There are other pieces of software bundled with jetty-rails. Before using jetty-rails, make sure you agree with all of them.


Comments are welcome. Send an email to Fabio Kung via the mailing list

Fabio Kung, 24th June 2009
Theme extended from Paul Battley