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Demystifying dRuby


• @makoto_inoue (@newbamboo)
• LRUG April 2012

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Who is Masatoshi Seki?

• Author of dRuby, Rinda, and ERB
• Ruby core committer (Rubyist since 1998)
• C by Day, Ruby by Night
• Never used Rails (Can't install!!)
• Pokemon Master

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Who is Masatoshi Seki?

Pokemon Master

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Who is Masatoshi Seki?

Pokemon Master

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Who is Masatoshi Seki?

Artist

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Who is Masatoshi Seki?

Resembles?

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What I want to talk about today

• dRuby == Creative & fun
• Mastering dRuby == Mastering Ruby
• Please buy the book(promo code in the last slide)

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Topics

• Basics of dRuby
• Internals of dRuby
• Pass by value, Pass by reference
• Rinda
• Drip

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Basics of dRuby

• Distributed Ruby
• 100% written in Ruby
• Part of Ruby Standard libraries
• Proxy to remote object

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Basics of dRuby

Server

@@@ ruby
require 'drb/drb'                                           
class Puts                                                  
  def initialize(stream=$stdout)
    @stream = stream
  end

  def puts(str)
    @stream.puts(str)
  end
end

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Basics of dRuby

Server

@@@ ruby
DRb.start_service(uri, Puts.new)                            
DRb.thread.join()

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Basics of dRuby

Client

@@@ ruby
require 'drb'
there = DRbObject.new_with_uri('druby://:12345')
there.puts("hello world")

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Basics of dRuby

Example

• http://www.screenr.com/embed/lO18 <iframe src="http://www.screenr.com/embed/lO18" width="650" height="396" frameborder="0"></iframe>

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Basics of dRuby

What you just learnt

• DRb.start_service
• DRbObject.new_with_uri
• DRb.thread.join()

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Internals of dRuby

Where is the source?

@@@ sh
[.rvm]$ find . -name 'drb' -print
./src/ruby-1.9.3-p0/lib/drb
./src/ruby-1.9.3-p0/sample/drb
./src/ruby-1.9.3-p0/test/drb

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Internals of dRuby

Let's play with same samples

@@@ sh
ruby  ~/.rvm/src/ruby-1.9.3-p0/sample/drb/drchats.rb
ruby  ~/.rvm/src/ruby-1.9.3-p0/sample/drb/drchatc.rb

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Internals of dRuby

The first dRuby

• 160 lines of code

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Internals of dRuby

Code Reading

• origin/drb_origin.rb

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Internals of dRuby

method_missing

@@@ruby
class DRbObject
  def method_missing(msg_id, *a)
    succ, result = DRbConn.new(@uri).
      send_message(self, msg_id, *a)
    raise result if ! succ
    result
  end

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Internals of dRuby

Marshall::Dump

@@@ruby
module DRbProtocol
  def dump(obj, soc)
    begin
      str = Marshal::dump(obj)

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Internals of dRuby

DRbObject.new(obj)

@@@ruby
    rescue
      ro = DRbObject.new(obj)
      str = Marshal::dump(ro)
    end
    soc.write(str) if soc
    return str
  end
end

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Internals of dRuby

What you learnt

• method_missing as proxy
• Marshal.dump everything
• If failed, dump DRbObject

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Pass by Value, Pass by Reference

Things you can not Marshal.dump

• IO,File, Socket, etc
• Proc

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Proc Example

Server

@@@ruby
front = {}
DRb.start_service('druby://:7640', front)
server_proc = Proc.new{ `pwd`}
front['server_proc'] = server_proc
while true
  sleep 1; puts "\n"; pp front;
  front.each { |k,v| p "#{k}:  #{v[]}"}
end

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Proc Example

Client

@@@ruby
DRb.start_service
remote = DRbObject.new_with_uri('druby://:7640')

client_proc = Proc.new{`pwd`}
remote['client_proc'] = client_proc

DRb.thread.join

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Proc Example

• http://www.screenr.com/embed/ZO18

  <iframe src="http://www.screenr.com/embed/ZO18" width="650" height="396" frameborder="0"></iframe>

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Proc Example

What you learnt

• Client is also Server
• DRbObject keeps reference

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Enumerable Example

Server

@@@ruby
require 'drb'
arry = Array.new(10){ Proc.new{ p `pwd`}}
DRb.start_service('druby://:7640', arry)
DRb.thread.join

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Enumerable Example

Client

require 'drb'
DRb.start_service
arry = DRbObject.new_with_uri('druby://:7640')

arry.each{|a| p `pwd`; a[]}

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Enumerable Example

• http://www.screenr.com/kO18

  <iframe src="http://www.screenr.com/embed/kO18" width="650" height="396" frameborder="0"></iframe>

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Enumerable Example

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Enumerable Example

What you learnt

• "each" happens locally
• "yield" happens remotely
• No "deadlock" thanks to Thread

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dRuby - use case

• Battleship
• Testing, Debugging, Monitoring utilities
• Network server for embedded tool(eg: Sqlite)

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Rinda

• Part of Ruby standard libraries
• Port of Linda
• Process Coordination Mechanism
• Distributed TupleSpace
• Share via dRuby

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Rinda

TupleSpace

@@@ ruby
['abc', 2, 5]
[:matrix, 1,6, 3.14]
['family', 'is-sister', 'Carolyn']

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Rinda

Operations

• write
• read, read_all
• take = read+delete

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Rinda

Example (TupleSpace)

@@@ruby
require 'drb/drb'
require 'rinda/tuplespace'
ts = Rinda::TupleSpace.new
DRb.start_service('druby://:7641', ts)
DRb.thread.join

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Rinda

Example

• http://www.screenr.com/Bp18

  <iframe src="http://www.screenr.com/embed/Bp18" width="650" height="396" frameborder="0"></iframe>

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Rinda

Pattern Matching

@@@ ruby
ts.take([/add|sub/, Integer])
ts.take([nil, (10..Float::INFINITY)])

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Rinda

===

@@@ ruby
class Njet
  def initialize(value)
    @value = value
  end

  def ===(other)
    ! (@value === other)
  end
end
ts.take['age', Njet.new(23)]

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Rinda

Other features

• notify (trigger)
• Hash API
• Ring (Name Server)

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Rinda - use case

• Simple task management tools
• Use it with "fork"(gem install rinda_eval)

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Seki san's current experiment

• PTupleSpace (2007) = Persisted tuplespace
• MapReduce, OODB (2009)
• Drip (2011) = Immutable datastore

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Drip

• gem install drip

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Drip

Immutable datastore

• Append Only
• Each data has key as time stamp
• Can traverse older/newer
• Can add "Tag"

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Drip

write(value, *tags)

@@@ruby
MyDrip.write(20, 'seki.age', 'male')
MyDrip.write(14, 'sora_h', 'male')
MyDrip.write(29, 'kate', 'female')

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Drip

read(key, n=1, at_least=1, timeout=nil)

@@@ruby
k = 0
while k 
  sleep 2
  r = MyDrip.read(k, 4, 1, 2)
  pp r; puts "\n"
  k = r[-1][0]
end

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Drip

head(n=1, tag=nil)

@@@ruby
k,v, *tags = MyDrip.head(1, 'male')[0]
# => [1333437978553705, 30, "will", "male"]

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Drip

older(key, tag=nil)

@@@ruby
k,v, *tags = MyDrip.older(k, 'male')

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Drip(Example)

• http://www.screenr.com/9X18

  <iframe src="http://www.screenr.com/embed/9X18" width="650" height="396" frameborder="0"></iframe>

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Drip

other operations

• newer
• read_tag
• []

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Drip - use case

• Hash with History
• Recoverable Queue
• Multicast Messaging
• Tweets archive
• Desktop search engine

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Summary

• dRuby = Feels like Ruby
• Rinda = Cool pattern matching
• Drip = Immutable datastore
• [name of your cool new distributed tools]

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Thank you

 * [@makoto_inoue](https://twitter.com/makoto_inoue) * [https://github.com/makoto](https://github.com/makoto/demystifying_druby_lrug_april_2012)