It is a translation of the original(in Japanese). Every header is linked to the corresponding original slide.

Distributed object environment by dRuby

<URL:http://www2a.biglobe.ne.jp/~seki/ruby/>

• Introduction
• Applications
• About its implementation
• Future

My life with dRuby

• I wanted to make it.
  • Extend Ruby objects across the net
  • So that you remote can handle it transparently
• I want it come into used.
  • Conquer the world < the problem is in front of you

dRuby is

• Ruby-limited distributed object environment
• 100% Pure Ruby
• RMI (in Java) style
• Without declaration (IDL/stub/skeleton)

dRuby functions

• Invoke method(s) of object(s) on other host(s)/process(es)
  • Treatment of the object(s) is same as usual
  • dRuby server, and also client
• Exchange objects
  • Return values, arguments
  • Call by value (default)
  • Change automatically to call by reference
• Support exception, method with block(=iterator)
• Support multithreading

dRuby world

• URI ... druby://hostname:port
• reference ... by URI + ID
  • The ID is determined at runtime
• front ... defined simply by URI
  • Persistent name
  • Frontgate of the system
  • The system made up by dRuby has more than zero fronts

dRuby world 2

• Nothing is known at first except URI
• Handle objects taught by front

dRuby world 3

• dRuby script...
  • Knows URI of front
  • Or, becomes front
• front
  • Naming service
  • Access control

Call by value, call by reference

• Default is 'call by value'
• dump/load by Marshal (serialization/reconstitution)
• Cannot dump File, Thread, Proc etc. -> exception
  • If it includes them, it fails.
  • Catch exception, and call by reference.
  • DRbUndump Mix-in
• Cannot load Unknown class
  • Examinating in DRbUnknown

Application

• Web application
  • RWiki
• Synchronize dRubys
  • Rinda

RWiki

• A Wiki Clone with articles written in RD
• Rewritable web page
• Architecture
  • Server ... dRuby
  • Web interface ... CGI/mod_ruby
  • Mail interface ... scarlet
• There's long preprocessing such as RD formatting
• CGI itself needs everytime formatting
• RWiki caches preformatted pages

• Ask front about Page, and handle it

RWiki rw-cgi

Load distribution by TupleSpace

• Thread synchronization is available
• in/out (get/put) data with TupleSpace
• 'in' gets data that matches pattern

• Candidate knows TupleSpace only
• Adds Engine, speeds it up

dRuby implementation

• Method invocation
• Protection from GC

Method invocation

• DRbObject forwards received messages to the referee
• method_missing ... invoked in the case of ungoverned method
• DRbObject#method_missing ... forward to URI'ed server
  • marshaling
• The server invokes the referee method
• The result is also marshaled

Structure of the message

• Each element consists of 'length' and 'Marshal.dump'

Reference solution

• DRbObject has URI and id
• URI specifies the server
• id specifies object in the server
• Every dynamically generated object has its own id
• When id = nil always same object is refered

GC

• Call by reference has GC risk
• Consider at programming level
  • Method with Block (Iterator)
  • Covered by algorithm
• Time limited GC protection
  • Keep certain time till the access

GCed example

• GCed even refered by DRbObject

Avoid GC by iterator

• v is not GCed on proc.call

DRbIdConv

• DRbIdConv exchanges reference and object
• to_id ... from object to ID
• to_obj ... from ID to object
• Object.id and ObjectSpace._id2ref

Time limited GC

• Change IdConv
• Register to_id with the front
• Expand its life by to_obj
• Thread keeper forgets dead Object of the front
• Protected from GC certain time till the last access

Security

• Elemental dRuby has nothing
• ACL
  • Protect by the host
• Examine irregular message
  • Huge packet
  • Invoke dangerous methods
    • instance_eval
    • How about inspect??

Development in progress

• 1.3
  • 1.3b (...then)
  • More than one DRbServer
  • security
  • mod_ruby support
• 2.0
  • Planning
  • Reuse socket
• ARb
  • AgentRuby
  • Twins DRb

Distributed debugger

• Daemon debuggable
  • By NaHi
  • Debugged RWiki

• Is free to debug distributed environment?
  • Plotting out by NaHi
  • Code tracing across the processes

Thank you

• Do try it!
• Welcome any feedback

<URL:http://www2a.biglobe.ne.jp/~seki/ruby/>

Contribution to here.