JMaglev public available

fabiokr · November 22, 2008, 9:31pm

Hi all,
I’m releasing my experiments with JRuby and Terracotta (
JRuby, sharing objects across multiple runtimes. JMagLev? | Fabio Kung),
so you can play with JMaglev and contribute some code.

I had to patch JRuby to make RubyObjects a little less dependent from
the
current 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:

github.com

fabiokung/clustered-jruby/blob/master/clustering_jruby.patch

Index: src/org/jruby/runtime/ReadonlyGlobalVariable.java
===================================================================
--- src/org/jruby/runtime/ReadonlyGlobalVariable.java	(revision 8091)
+++ src/org/jruby/runtime/ReadonlyGlobalVariable.java	(working copy)
@@ -34,12 +34,12 @@
 
 public class ReadonlyGlobalVariable extends GlobalVariable {
 
-    public ReadonlyGlobalVariable(Ruby runtime, String name, IRubyObject value) {
-        super(runtime, name, value);
+    public ReadonlyGlobalVariable(String name, IRubyObject value) {
+        super(name, value);
     }
 
     @Override
     public IRubyObject set(IRubyObject value) {
-        throw runtime.newNameError(name() + " is a read-only variable", name());
+        throw Ruby.getCurrentRuntime().newNameError(name() + " is a read-only variable", name());
     }
 }

This file has been truncated. show original

The github project 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.

For those who want to reproduce my JMaglev demo, here is a step-by-step:

REQUIREMENTS: git, mvn and jdk 1.5

git clone git://github.com/fabiokung/clustered-jruby.git
long time waiting, because terracotta-2.7.1 and jruby-complete are
bundled.
cd clustered-jruby
mvn install (although ‘mvn package’ is enough)
cd jmaglev
start the terracotta server:
lib/terracotta-2.7.1/bin/start-tc-server.sh
open another two terminals
run the simplified jirb inside them:
cd clustered-jruby/jmaglev
./bin/jmaglev jmaglev.rb
follow the demo. You will be able to share global variables among all
jmaglevs:
require ‘hat’
$hat
require ‘rabbit’
$hat.put(Rabbit.new)
in the other terminal, try to see the “magic hat” contents:
$hat

Now the hard part. My patch forces JRuby to use the same Runtime
almost every time (per JVM). Unfortunately I haven’t much time (and
competency) yet to spend on this.

One idea (from Charles) to support many runtimes for each JVM, is to
always
retrieve the current Runtime from the classloader that loaded the class.
I
would have to use a different classloader for each JRuby Runtime
instance,
and probably it would require shared jruby objects to be serialized
between
different runtimes, in the same JVM! (argh, are you also thinking in
local-EJB calls?).

I’m taking the easy path and just supporting one-runtime-per-jvm by
now. Perhaps, with the new thread-safe Rails, multiple runtimes inside
one
JVM are becoming less needed. Does anyone know other useful cases for
multiple runtimes per JVM?

Another thing you may discover (and I know), is that code for this part
is
ugly. Here are some places to look:

org.jruby.Ruby#Ruby
org.jruby.Ruby#getCurrentRuntime

I’m keeping the last created Ruby Runtime inside the current
classloader. As
I’m always using the same classloader, I’m also using the same Runtime.
This
is the same as a static field somewhere and you can help me here.

Another way is to make a huge change to JRuby architecture, and always
pass
Runtimes as method parameters, whenever needed.

What do you think? Any other ideas?

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.

I hope to see many contributions. Happy hacking!

Cheers,

Fabio K.

Caelum - Ensino e InovaÃ§Ã£o
http://www.caelum.com.br

fabiokr · November 23, 2008, 6:12am

This is great, Fabio, thank you for releasing this. Are you going to
post another blog entry showing how others can try this out?

Fabio K. wrote:

patch against the current jruby trunk (rev. 8091) and the patched
REQUIREMENTS: git, mvn and jdk 1.5
5) cd jmaglev
9) follow the demo. You will be able to share global variables among all
almost every time (per JVM). Unfortunately I haven’t much time (and
now. Perhaps, with the new thread-safe Rails, multiple runtimes inside
classloader. As I’m always using the same classloader, I’m also using

I hope to see many contributions. Happy hacking!

Cheers,

Fabio K.
http://www.fabiokung.com

Caelum - Ensino e InovaÃ§Ã£o
http://www.caelum.com.br

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fabiokr · November 23, 2008, 6:27am

Yes, I’ve already posted on my blog:

Thanks!

On Sun, Nov 23, 2008 at 3:12 AM, Charles Oliver N. <
[email protected]> wrote:

so you can play with JMaglev and contribute some code.

long time waiting, because terracotta-2.7.1 and jruby-complete are

require ‘rabbit’
always retrieve the current Runtime from the classloader that loaded the
Another thing you may discover (and I know), is that code for this part is
pass Runtimes as method parameters, whenever needed.
Fabio K.
http://xircles.codehaus.org/manage_email

–
Fabio K.

Caelum - Ensino e InovaÃ§Ã£o
http://www.caelum.com.br

fabiokr · November 23, 2008, 6:38am

Oh, nevermind, I just saw your post from today

Charles Oliver N. wrote:

GitHub - fabiokung/clustered-jruby: Cluster Configuration for JRuby, using Terracotta.
a sample maven project and the JMaglev use-case included.
bundled.
7) open another two terminals
$hat.put(Rabbit.new)
the class. I would have to use a different classloader for each JRuby
part is ugly. Here are some places to look:
pass Runtimes as method parameters, whenever needed.
Fabio K.

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