These slides show a high level architecture of Ruby MagLev as well as a small example to illustrate how easy it is to have transparent object persistence in Ruby.

1. An introduction to Maglev
Rudi Engelbrecht
Ruby Conf - 17 June 2011
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2. MagLev Concepts
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3. MagLev Concepts
• Root Object
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4. MagLev Concepts
• Root Object
• Persistency by Reachability
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5. MagLev Concepts
• Root Object
• Persistency by Reachability
• (transitive closure)
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6. MagLev Concepts
• Root Object
• Persistency by Reachability
• (transitive closure)
• Repository (Stone)
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7. MagLev Concepts
• Root Object
• Persistency by Reachability
• (transitive closure)
• Repository (Stone)
• Virtual Machines (Gems)
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8. MagLev Concepts
• Root Object
• Persistency by Reachability
• (transitive closure)
• Repository (Stone)
• Virtual Machines (Gems)
• local vs remote gems
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9. MagLev Concepts
• Root Object
• Persistency by Reachability
• (transitive closure)
• Repository (Stone)
• Virtual Machines (Gems)
• local vs remote gems
• Garbage Collector
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10. Ruby
VM
Ruby
VM Shared
Page Repository
Cache
Ruby
VM
Ruby
VM

12. TwitterClone
class Person def remove_follower(person)
@followers.delete(person)
attr_accessor :username, :followers end
def initialize(username) def to_s
@username = username result = "@#{@username} -->
@followers = Array.new [#{@followers.size}]"
end @followers.each {|f| result = result +
" #{f.username}" }
def add_follower(person) result
@followers << person end
end end
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13. TwitterClone
Maglev.persistent do
require 'person'
end
Maglev::PERSISTENT_ROOT[:persons] = Array.new
Maglev.commit_transaction
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17. person.rb

18. person.rb
person.rb

19. :persons
Array
person.rb
person.rb

20. :persons
Array
:persons
Array
person.rb
person.rb
person.rb

21. TwitterClone
require 'person'
dhh = Person.new("dhh") persons =
obie = Person.new("obie") Maglev::PERSISTENT_ROOT[:persons]
unclebob = Person.new("unclebob")
noob1 = Person.new("noob1") persons << dhh
noob2 = Person.new("noob2") persons << obie
persons << unclebob
dhh.add_follower(obie)
dhh.add_follower(unclebob) Maglev.commit_transaction
obie.add_follower(unclebob)
unclebob.add_follower(noob1)
unclebob.add_follower(noob2)
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25. :persons
Array
:persons
Array

26. :persons
Array
dhh :persons
Array

27. :persons
Array
dhh obie :persons
Array

28. :persons
Array
dhh obie :persons
unclebob Array

29. :persons
Array
dhh obie :persons
unclebob Array

30. :persons
Array
dhh obie :persons
unclebob Array

31. :persons
Array
dhh obie :persons
unclebob Array

32. :persons
Array
dhh obie :persons
unclebob Array
noob1

33. :persons
Array
dhh obie :persons
unclebob Array
noob1 noob2

34. :persons
Array
dhh obie :persons
unclebob Array
noob1 dhh obie
noob2
unclebob
noob1 noob2

35. TwitterClone
persons = Maglev::PERSISTENT_ROOT[:persons]
persons.each {|p| puts p}
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36. TwitterClone
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37. TwitterClone
• Multiple VM’s
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38. TwitterClone
• Multiple VM’s
• Concurrent access - MVCC
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39. TwitterClone
• Multiple VM’s
• Concurrent access - MVCC
• First commit wins
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40. TwitterClone2 def add_follower(person)
class Person @followers << person
attr_accessor :username, :email, :followers, :following end
def initialize(username) def remove_follower(person)
@username = username @followers.delete(person)
@email = username + "@mail.com" end
@followers = Array.new
@following = Array.new def to_s
end result = "@#{@username} --> [#{@following.size} :
#{@followers.size}]"
def follows(person) result = result + " following: {"
@following << person @following.each {|f| result = result + " #{f.username}"}
person.add_follower(self) result = result + " }"
end result = result + " followed by: {"
@followers.each {|f| result = result + " #{f.username}"}
def unfollows(person) result = result + " }"
@following.delete(person) result
person.remove_follower(self) end
end end
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41. TwitterClone2
Maglev.persistent do
require 'person'
end
Maglev::PERSISTENT_ROOT[:persons] = Array.new
Maglev.commit_transaction
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42. TwitterClone2
require 'person'
dhh = Person.new("dhh")
obie = Person.new("obie")
unclebob = Person.new("unclebob")
noob1 = Person.new("noob1")
noob2 = Person.new("noob2")
obie.follows(dhh)
unclebob.follows(dhh)
unclebob.follows(obie)
noob1.follows(unclebob)
noob2.follows(unclebob)
persons = Maglev::PERSISTENT_ROOT[:persons]
persons << dhh
persons << obie
persons << unclebob
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43. TwitterClone2
persons = Maglev::PERSISTENT_ROOT[:persons]
persons.each {|p| puts p}
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44. MagLev
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45. MagLev
• Concurrent access to objects in distributed VM’s
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46. MagLev
• Concurrent access to objects in distributed VM’s
• Rabbit in hat trick
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47. MagLev
• Concurrent access to objects in distributed VM’s
• Rabbit in hat trick
• Proc’s can be persisted
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48. MagLev
• Concurrent access to objects in distributed VM’s
• Rabbit in hat trick
• Proc’s can be persisted
• references enclosing environment’s variables
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49. Dinner
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50. Dinner
• Enjoy!
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