Category Archives: terracotta

Play with JMaglev yourself

JMaglev is finally public available!

I’m releasing my experiments with JRuby and Terracotta, so you can play with JMaglev and contribute some code. The project is in Github.

I had to patch JRuby to make RubyObjects a little less dependent from the JRuby Runtime. It isn’t perfect yet, but is working. The patch against the current jruby trunk (rev. 8091) and the patched jruby-complete are included in the project.

The code in Github is just a TIM (Terracotta Integration Module) with a sample maven project and the JMaglev use-case included. Unfortunately, I haven’t any time yet to upload the TIM to Terracotta Forge. BTW, does anyone know how to do this?

For those who want to reproduce my JMaglev demo, here is a step-by-step. You must have GIT, Maven 2 and the JDK properly installed. It only works on Linux and OS X. Is anyone wanting to contribute support for Windows users?

  1. git clone git://github.com/fabiokung/clustered-jruby.git
  2. long time waiting, because terracotta-2.7.1 (vanilla) and jruby-complete (patched) are bundled.
  3. cd clustered-jruby
  4. mvn install (although mvn package is enough)
  5. cd jmaglev
  6. start the terracotta server:
    lib/terracotta-2.7.1/bin/start-tc-server.sh
  7. open another two terminals
  8. run the simplified jirb inside them:

    9. cd clustered-jruby/jmaglev
./bin/jmaglev jmaglev.rb

  9. Follow the demo. You will be able to share global variables among all jmaglevs: 
    require 'hat'
$hat
require 'rabbit'
$hat.put(Rabbit.new)
  10. in the other terminal, try to see the magic hat contents: 
    $hat

I haven’t tested it with rails applications, but right now, it isn’t able to run IRB. I never thought that running IRB could be so hard. 🙂

More drawbacks and limitations are being discussed in the JRuby Users Mailing List.

I hope to see many contributions. Happy hacking!

JRuby, sharing objects across multiple runtimes. JMagLev?

MagLev was a show from the last RailsConf (2008). Presentation and demos of the product are really impressive.

Recently, Brian Takita asked in the JRuby mailing list:

JRuby + TerraCotta == Maglev?

What an idea! In the last few days I’ve tried to make something useful and I’m happy to have something to show.

JRuby + Nailgun and JRuby + Terracotta

Screencast: Reproducing Avi Bryant's Demo with JRuby + Nailgun and JRuby + Terracotta. (5 min)

The first demo runs with Nailgun. The basic idea is to share a single Java VM across all clients, so they can share some objects. The second is much more complete, as its clients have their own Java VM. There are many true interpreters running, and they are sharing objects through Terracotta. Terracotta is responsible for sharing memory in Java VM clusters and, despite of its slow startup, has much more to offer. The shared objects (hats and rabbits) could be automatically persisted by Terracotta, as MagLev also does.

I’ve patched JRuby and configured Terracotta to make demos run. I’ll upload the patches and configuration somewhere, ASAP.

Working on JRuby to make it run multiple runtimes (VMs) at the same time is being really fun!