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Maglev Rubyfuza, Cape Town, 2012
- 1. Exploring Maglev Rudi Engelbrecht Rubyfuza, Cape Town, 2-3 Feb 2012 lautus
- 2. MagLev History Rubyfuza - Cape Town - 2012
- 3. MagLev History • Smalltalk Virtual Machine Rubyfuza - Cape Town - 2012
- 4. MagLev History • Smalltalk Virtual Machine • Mature, used in production, large sites Rubyfuza - Cape Town - 2012
- 5. MagLev History • Smalltalk Virtual Machine • Mature, used in production, large sites • GemStone Rubyfuza - Cape Town - 2012
- 6. MagLev History • Smalltalk Virtual Machine • Mature, used in production, large sites • GemStone • Transactional Memory Object Server for Smalltalk Rubyfuza - Cape Town - 2012
- 7. MagLev History • Smalltalk Virtual Machine • Mature, used in production, large sites • GemStone • Transactional Memory Object Server for Smalltalk • Maglev Rubyfuza - Cape Town - 2012
- 8. MagLev History • Smalltalk Virtual Machine • Mature, used in production, large sites • GemStone • Transactional Memory Object Server for Smalltalk • Maglev • Transactional Memory Object Server for Ruby Rubyfuza - Cape Town - 2012
- 9. MagLev Concepts Rubyfuza - Cape Town - 2012
- 10. MagLev Concepts • Root Object Rubyfuza - Cape Town - 2012
- 11. MagLev Concepts • Root Object • Persistency by Reachability Rubyfuza - Cape Town - 2012
- 12. MagLev Concepts • Root Object • Persistency by Reachability • transitive closure Rubyfuza - Cape Town - 2012
- 13. MagLev Concepts • Root Object • Persistency by Reachability • transitive closure • Repository Rubyfuza - Cape Town - 2012
- 14. MagLev Concepts • Root Object • Persistency by Reachability • transitive closure • Repository • Ruby Virtual Machines Rubyfuza - Cape Town - 2012
- 15. MagLev Concepts • Root Object • Persistency by Reachability • transitive closure • Repository • Ruby Virtual Machines • local vs remote virtual machines Rubyfuza - Cape Town - 2012
- 16. MagLev Concepts • Root Object • Persistency by Reachability • transitive closure • Repository • Ruby Virtual Machines • local vs remote virtual machines • Garbage Collector Rubyfuza - Cape Town - 2012
- 17. MagLev Concepts Rubyfuza - Cape Town - 2012
- 18. MagLev Concepts • Transparent Object Persistence Rubyfuza - Cape Town - 2012
- 19. MagLev Concepts • Transparent Object Persistence • Large Object Space Rubyfuza - Cape Town - 2012
- 20. MagLev Concepts • Transparent Object Persistence • Large Object Space • limited by disk space (not RAM) Rubyfuza - Cape Town - 2012
- 21. MagLev Concepts • Transparent Object Persistence • Large Object Space • limited by disk space (not RAM) • Multi-user Rubyfuza - Cape Town - 2012
- 22. MagLev Concepts • Transparent Object Persistence • Large Object Space • limited by disk space (not RAM) • Multi-user • Thousands of virtual machines Rubyfuza - Cape Town - 2012
- 23. MagLev Concepts • Transparent Object Persistence • Large Object Space • limited by disk space (not RAM) • Multi-user • Thousands of virtual machines • Sharing one object space Rubyfuza - Cape Town - 2012
- 24. MagLev Concepts • Transparent Object Persistence • Large Object Space • limited by disk space (not RAM) • Multi-user • Thousands of virtual machines • Sharing one object space • Isolation of each user’s view (repeatable read) Rubyfuza - Cape Town - 2012
- 25. MagLev Concepts Rubyfuza - Cape Town - 2012
- 26. MagLev Concepts • Concurrency Rubyfuza - Cape Town - 2012
- 27. MagLev Concepts • Concurrency • Multi Version Concurrency Control Rubyfuza - Cape Town - 2012
- 28. MagLev Concepts • Concurrency • Multi Version Concurrency Control • Optimistic and Pessimistic models Rubyfuza - Cape Town - 2012
- 29. MagLev Concepts • Concurrency • Multi Version Concurrency Control • Optimistic and Pessimistic models • Stores any Ruby Object Rubyfuza - Cape Town - 2012
- 30. MagLev Concepts • Concurrency • Multi Version Concurrency Control • Optimistic and Pessimistic models • Stores any Ruby Object • including it’s code (methods) Rubyfuza - Cape Town - 2012
- 31. Ruby VM Ruby VM Shared Page Repository Cache Ruby VM Ruby VM
- 32. Ruby VM Repository Ruby VM
- 33. MagLev - Magic Hat Rubyfuza - Cape Town - 2012
- 34. MagLev - Magic Hat • Rabbit in Hat Trick Rubyfuza - Cape Town - 2012
- 35. class Person attr_accessor :username, :followers def initialize(username) @username = username @followers = Array.new end def add_follower(person) @followers << person end def remove_follower(person) @followers.delete(person) end def to_s result = "@#{@username} --> [#{@followers.size}]" @followers.each {|f| result = result + " #{f.username}" } result end end Rubyfuza - Cape Town - 2012
- 36. class Person attr_accessor :username, :followers def initialize(username) @username = username @followers = Array.new end ... end Rubyfuza - Cape Town - 2012
- 37. ... def add_follower(person) @followers << person end def remove_follower(person) @followers.delete(person) end ... Rubyfuza - Cape Town - 2012
- 38. ... def to_s result = "@#{@username} --> [#{@followers.size}]" @followers.each {|f| result = result + " #{f.username}" } result end ... Rubyfuza - Cape Town - 2012
- 39. Maglev.persistent do require 'person' end Maglev::PERSISTENT_ROOT[:persons] = Array.new Maglev.commit_transaction Rubyfuza - Cape Town - 2012
- 43. person.rb
- 45. :persons Array person.rb person.rb
- 46. :persons Array :persons Array person.rb person.rb person.rb
- 47. persons = Maglev::PERSISTENT_ROOT[:persons] persons.each {|p| puts p} Rubyfuza - Cape Town - 2012
- 48. require 'person' dhh = Person.new("dhh") obie = Person.new("obie") unclebob = Person.new("unclebob") noob1 = Person.new("noob1") noob2 = Person.new("noob2") dhh.add_follower(obie) dhh.add_follower(unclebob) obie.add_follower(unclebob) unclebob.add_follower(noob1) unclebob.add_follower(noob2) persons = Maglev::PERSISTENT_ROOT[:persons] persons << dhh persons << obie persons << unclebob Maglev.commit_transaction Rubyfuza - Cape Town - 2012
- 52. :persons Array :persons Array
- 53. :persons Array dhh :persons Array
- 54. :persons Array dhh obie :persons Array
- 55. :persons Array dhh obie :persons unclebob Array
- 56. :persons Array dhh obie :persons unclebob Array
- 57. :persons Array dhh obie :persons unclebob Array
- 58. :persons Array dhh obie :persons unclebob Array
- 59. :persons Array dhh obie :persons unclebob Array noob1
- 60. :persons Array dhh obie :persons unclebob Array noob1 noob2
- 61. :persons Array dhh obie :persons unclebob Array noob1 dhh obie noob2 unclebob noob1 noob2
- 62. TwitterClone2 Rubyfuza - Cape Town - 2012
- 63. TwitterClone2 • Improved design Rubyfuza - Cape Town - 2012
- 64. TwitterClone2 • Improved design • Multiple VM’s Rubyfuza - Cape Town - 2012
- 65. TwitterClone2 • Improved design • Multiple VM’s • Concurrent access - MVCC Rubyfuza - Cape Town - 2012
- 66. TwitterClone2 • Improved design • Multiple VM’s • Concurrent access - MVCC • First commit wins Rubyfuza - Cape Town - 2012
- 67. class Person attr_accessor :username, :email, :followers, :following, :tweets def initialize(username) @username = username @email = username + “@email.com” @followers = Array.new @following = Array.new @tweets = Array.new end ... end Rubyfuza - Cape Town - 2012
- 68. ... def follows(person) @following << person person.add_follower(self) end def unfollows(person) @following.delete(person) person.remove_follower(self) end ... Rubyfuza - Cape Town - 2012
- 69. ... def add_follower(person) @followers << person end def remove_follower(person) @followers.delete(person) end ... Rubyfuza - Cape Town - 2012
- 70. ... def tweets(text) @tweets << Tweet.new(self, text) end ... Rubyfuza - Cape Town - 2012
- 71. ... def to_s result = "@#{@username} tweeted #{@tweets.size} times, follows #{@following.size} persons and is followed #{@followers.size} times" result = result + " , following: {" @following.each {|f| result = result + " #{f.username}"} result = result + " }" result = result + " followed by: {" @followers.each {|f| result = result + " #{f.username}"} result = result + " }" result end ... Rubyfuza - Cape Town - 2012
- 72. Maglev.persistent do require 'person' require 'tweet' end Maglev::PERSISTENT_ROOT[:persons] = Array.new Maglev.commit_transaction Rubyfuza - Cape Town - 2012
- 73. persons = Maglev::PERSISTENT_ROOT[:persons] persons.each {|p| puts p} Rubyfuza - Cape Town - 2012
- 74. 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 Maglev.commit_transaction Rubyfuza - Cape Town - 2012
- 75. dhh obie followers dhh followers obie following following unclebob followers dhh Concurrent updates (in different VM’s) following to same object fails
- 76. dhh obie followers dhh followers obie following following unclebob followers dhh Concurrent updates (in different VM’s) following to same object fails
- 77. :persons Array dhh obie followers dhh followers obie dhh obie following following unclebob noob1 noob2 unclebob followers dhh Concurrent updates (in different VM’s) following to same object fails
- 78. :persons Array dhh obie followers dhh followers obie dhh obie following following unclebob noob1 noob2 unclebob followers dhh Concurrent updates (in different VM’s) following to same object fails
- 79. :persons Array dhh obie followers dhh followers obie dhh obie following following unclebob noob1 noob2 unclebob followers dhh Concurrent updates (in different VM’s) following to same object fails
- 80. :persons Array dhh obie followers dhh followers obie dhh obie following following unclebob noob1 noob2 unclebob followers dhh Concurrent updates (in different VM’s) following to same object fails
- 81. MagLev - Locks Rubyfuza - Cape Town - 2012
- 82. MagLev - Locks • Read lock on object Rubyfuza - Cape Town - 2012
- 83. MagLev - Locks • Read lock on object • Use object’s value and commit without fear that some other transaction has committed a new value for that object during your transaction Rubyfuza - Cape Town - 2012
- 84. MagLev - Locks • Read lock on object • Use object’s value and commit without fear that some other transaction has committed a new value for that object during your transaction • Guarantees that other sessions cannot: a) acquire a write lock on the object b) commit if they have written the object Rubyfuza - Cape Town - 2012
- 85. MagLev - Locks Rubyfuza - Cape Town - 2012
- 86. MagLev - Locks • Write lock on object Rubyfuza - Cape Town - 2012
- 87. MagLev - Locks • Write lock on object • Guarantees that you can write the object and commit. Rubyfuza - Cape Town - 2012
- 88. MagLev - Locks • Write lock on object • Guarantees that you can write the object and commit. • Guarantees that other sessions cannot: a) acquire a read or write lock on the object b) commit if they have written the object Rubyfuza - Cape Town - 2012
- 89. MagLev - Locks • Write lock on object • Guarantees that you can write the object and commit. • Guarantees that other sessions cannot: a) acquire a read or write lock on the object b) commit if they have written the object • Only one session can hold a write lock on an object - no other session can hold any kind of lock on the object. Rubyfuza - Cape Town - 2012
- 90. MagLev - Procs y = 4 proc = Proc.new {|x| x * y} proc.call(4) Rubyfuza - Cape Town - 2012
- 91. MagLev - Continuation Thread.start { callcc {|cc| $cont = cc}; p “Run after One pretty callcc” } Maglev::PERSISTENT_ROOT[:cc] = $cont Maglev.commit_transaction Rubyfuza - Cape Town - 2012
- 92. MagLev - Continuation Maglev.abort_transaction $cont = Maglev::PERSISTENT_ROOT[:cc] Thread.start {$cont.call} Rubyfuza - Cape Town - 2012
- 93. MagLev - Summary Rubyfuza - Cape Town - 2012
- 94. MagLev - Summary • Rabbit in hat trick Rubyfuza - Cape Town - 2012
- 95. MagLev - Summary • Rabbit in hat trick • Concurrent access to objects in distributed VM’s Rubyfuza - Cape Town - 2012
- 96. MagLev - Summary • Rabbit in hat trick • Concurrent access to objects in distributed VM’s • Proc’s can be persisted Rubyfuza - Cape Town - 2012
- 97. MagLev - Summary • Rabbit in hat trick • Concurrent access to objects in distributed VM’s • Proc’s can be persisted • references enclosing environment’s variables Rubyfuza - Cape Town - 2012
- 98. MagLev - Summary • Rabbit in hat trick • Concurrent access to objects in distributed VM’s • Proc’s can be persisted • references enclosing environment’s variables • Continuations Rubyfuza - Cape Town - 2012
- 99. MagLev - Summary • Rabbit in hat trick • Concurrent access to objects in distributed VM’s • Proc’s can be persisted • references enclosing environment’s variables • Continuations • Queue Rubyfuza - Cape Town - 2012
- 100. MagLev - Summary • Rabbit in hat trick • Concurrent access to objects in distributed VM’s • Proc’s can be persisted • references enclosing environment’s variables • Continuations • Queue • see example on github/maglev Rubyfuza - Cape Town - 2012
- 101. Credits Monty Williams GemStone http://maglev.github.com/docs/learn.html https://github.com/MagLev/maglev Conrad Taylor Playing with Maglev the Ruby VM http://www.conradtaylor.com/2011/11/08/playing-with-maglev-the- ruby-vm/ Tim Felgentreff Debugging on Steroids - what Ruby should learn from Smalltalk http://blog.bithug.org/2011/09/maglev-debug Rubyfuza - Cape Town - 2012
- 102. Questions • Updates on Twitter @rudiengelbrecht • Slides on SlideShare • Source code on GitHub userid - rle Rubyfuza - Cape Town - 2012
Editor's Notes
- \n
- gcgem\n
- gcgem\n
- gcgem\n
- gcgem\n
- gcgem\n
- gcgem\n
- gcgem\n
- gcgem\n
- gcgem\n
- gcgem\n
- gcgem\n
- gcgem\n
- gcgem\n
- gcgem\n
- gcgem\n
- gcgem\n
- gcgem\n
- gcgem\n
- gcgem\n
- gcgem\n
- Consistency levels\nDegree 0 - None\nDegree 1 - Locking READ UNCOMMITTED\nDegree 2 - Locking READ COMMITTED\nLocking REPEATABLE READ\nDegree 3 - Locking SERIALIZABLE\n
- Consistency levels\nDegree 0 - None\nDegree 1 - Locking READ UNCOMMITTED\nDegree 2 - Locking READ COMMITTED\nLocking REPEATABLE READ\nDegree 3 - Locking SERIALIZABLE\n
- Consistency levels\nDegree 0 - None\nDegree 1 - Locking READ UNCOMMITTED\nDegree 2 - Locking READ COMMITTED\nLocking REPEATABLE READ\nDegree 3 - Locking SERIALIZABLE\n
- Consistency levels\nDegree 0 - None\nDegree 1 - Locking READ UNCOMMITTED\nDegree 2 - Locking READ COMMITTED\nLocking REPEATABLE READ\nDegree 3 - Locking SERIALIZABLE\n
- Consistency levels\nDegree 0 - None\nDegree 1 - Locking READ UNCOMMITTED\nDegree 2 - Locking READ COMMITTED\nLocking REPEATABLE READ\nDegree 3 - Locking SERIALIZABLE\n
- Logical Architecture\n
- Demonstration architecture\nRoot object - carrot orange\n
- show hat, rabbit and cat\n
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- owynn = Person.new("Owynn")\nunclebob = persons[0].followers[1]\nunclebob.add_follower(owynn)\n
- note the persistence by reachability\ncould also just add dhh\nshow persons[0].followers[0].followers[0].followers[1] is the reference to noob2\nalso persons[0].followers[1].followers[1] is reference to noob2\n
- note the persistence by reachability\ncould also just add dhh\nshow persons[0].followers[0].followers[0].followers[1] is the reference to noob2\nalso persons[0].followers[1].followers[1] is reference to noob2\n
- note the persistence by reachability\ncould also just add dhh\nshow persons[0].followers[0].followers[0].followers[1] is the reference to noob2\nalso persons[0].followers[1].followers[1] is reference to noob2\n
- note the persistence by reachability\ncould also just add dhh\nshow persons[0].followers[0].followers[0].followers[1] is the reference to noob2\nalso persons[0].followers[1].followers[1] is reference to noob2\n
- note the persistence by reachability\ncould also just add dhh\nshow persons[0].followers[0].followers[0].followers[1] is the reference to noob2\nalso persons[0].followers[1].followers[1] is reference to noob2\n
- note the persistence by reachability\ncould also just add dhh\nshow persons[0].followers[0].followers[0].followers[1] is the reference to noob2\nalso persons[0].followers[1].followers[1] is reference to noob2\n
- note the persistence by reachability\ncould also just add dhh\nshow persons[0].followers[0].followers[0].followers[1] is the reference to noob2\nalso persons[0].followers[1].followers[1] is reference to noob2\n
- note the persistence by reachability\ncould also just add dhh\nshow persons[0].followers[0].followers[0].followers[1] is the reference to noob2\nalso persons[0].followers[1].followers[1] is reference to noob2\n
- note the persistence by reachability\ncould also just add dhh\nshow persons[0].followers[0].followers[0].followers[1] is the reference to noob2\nalso persons[0].followers[1].followers[1] is reference to noob2\n
- note the persistence by reachability\ncould also just add dhh\nshow persons[0].followers[0].followers[0].followers[1] is the reference to noob2\nalso persons[0].followers[1].followers[1] is reference to noob2\n
- note the persistence by reachability\ncould also just add dhh\nshow persons[0].followers[0].followers[0].followers[1] is the reference to noob2\nalso persons[0].followers[1].followers[1] is reference to noob2\n
- note the persistence by reachability\ncould also just add dhh\nshow persons[0].followers[0].followers[0].followers[1] is the reference to noob2\nalso persons[0].followers[1].followers[1] is reference to noob2\n
- note the persistence by reachability\ncould also just add dhh\nshow persons[0].followers[0].followers[0].followers[1] is the reference to noob2\nalso persons[0].followers[1].followers[1] is reference to noob2\n
- note the persistence by reachability\ncould also just add dhh\nshow persons[0].followers[0].followers[0].followers[1] is the reference to noob2\nalso persons[0].followers[1].followers[1] is reference to noob2\n
- note the persistence by reachability\ncould also just add dhh\nshow persons[0].followers[0].followers[0].followers[1] is the reference to noob2\nalso persons[0].followers[1].followers[1] is reference to noob2\n
- note the persistence by reachability\ncould also just add dhh\nshow persons[0].followers[0].followers[0].followers[1] is the reference to noob2\nalso persons[0].followers[1].followers[1] is reference to noob2\n
- note the persistence by reachability\ncould also just add dhh\nshow persons[0].followers[0].followers[0].followers[1] is the reference to noob2\nalso persons[0].followers[1].followers[1] is reference to noob2\n
- note the persistence by reachability\ncould also just add dhh\nshow persons[0].followers[0].followers[0].followers[1] is the reference to noob2\nalso persons[0].followers[1].followers[1] is reference to noob2\n
- note the persistence by reachability\ncould also just add dhh\nshow persons[0].followers[0].followers[0].followers[1] is the reference to noob2\nalso persons[0].followers[1].followers[1] is reference to noob2\n
- note the persistence by reachability\ncould also just add dhh\nshow persons[0].followers[0].followers[0].followers[1] is the reference to noob2\nalso persons[0].followers[1].followers[1] is reference to noob2\n
- note the persistence by reachability\ncould also just add dhh\nshow persons[0].followers[0].followers[0].followers[1] is the reference to noob2\nalso persons[0].followers[1].followers[1] is reference to noob2\n
- note the persistence by reachability\ncould also just add dhh\nshow persons[0].followers[0].followers[0].followers[1] is the reference to noob2\nalso persons[0].followers[1].followers[1] is reference to noob2\n
- note the persistence by reachability\ncould also just add dhh\nshow persons[0].followers[0].followers[0].followers[1] is the reference to noob2\nalso persons[0].followers[1].followers[1] is reference to noob2\n
- note the persistence by reachability\ncould also just add dhh\nshow persons[0].followers[0].followers[0].followers[1] is the reference to noob2\nalso persons[0].followers[1].followers[1] is reference to noob2\n
- note the persistence by reachability\ncould also just add dhh\nshow persons[0].followers[0].followers[0].followers[1] is the reference to noob2\nalso persons[0].followers[1].followers[1] is reference to noob2\n
- note the persistence by reachability\ncould also just add dhh\nshow persons[0].followers[0].followers[0].followers[1] is the reference to noob2\nalso persons[0].followers[1].followers[1] is reference to noob2\n
- note the persistence by reachability\ncould also just add dhh\nshow persons[0].followers[0].followers[0].followers[1] is the reference to noob2\nalso persons[0].followers[1].followers[1] is reference to noob2\n
- note the persistence by reachability\ncould also just add dhh\nshow persons[0].followers[0].followers[0].followers[1] is the reference to noob2\nalso persons[0].followers[1].followers[1] is reference to noob2\n
- note the persistence by reachability\ncould also just add dhh\nshow persons[0].followers[0].followers[0].followers[1] is the reference to noob2\nalso persons[0].followers[1].followers[1] is reference to noob2\n
- note the persistence by reachability\ncould also just add dhh\nshow persons[0].followers[0].followers[0].followers[1] is the reference to noob2\nalso persons[0].followers[1].followers[1] is reference to noob2\n
- note the persistence by reachability\ncould also just add dhh\nshow persons[0].followers[0].followers[0].followers[1] is the reference to noob2\nalso persons[0].followers[1].followers[1] is reference to noob2\n
- note the persistence by reachability\ncould also just add dhh\nshow persons[0].followers[0].followers[0].followers[1] is the reference to noob2\nalso persons[0].followers[1].followers[1] is reference to noob2\n
- note the persistence by reachability\ncould also just add dhh\nshow persons[0].followers[0].followers[0].followers[1] is the reference to noob2\nalso persons[0].followers[1].followers[1] is reference to noob2\n
- note the persistence by reachability\ncould also just add dhh\nshow persons[0].followers[0].followers[0].followers[1] is the reference to noob2\nalso persons[0].followers[1].followers[1] is reference to noob2\n
- note the persistence by reachability\ncould also just add dhh\nshow persons[0].followers[0].followers[0].followers[1] is the reference to noob2\nalso persons[0].followers[1].followers[1] is reference to noob2\n
- note the persistence by reachability\ncould also just add dhh\nshow persons[0].followers[0].followers[0].followers[1] is the reference to noob2\nalso persons[0].followers[1].followers[1] is reference to noob2\n
- note the persistence by reachability\ncould also just add dhh\nshow persons[0].followers[0].followers[0].followers[1] is the reference to noob2\nalso persons[0].followers[1].followers[1] is reference to noob2\n
- note the persistence by reachability\ncould also just add dhh\nshow persons[0].followers[0].followers[0].followers[1] is the reference to noob2\nalso persons[0].followers[1].followers[1] is reference to noob2\n
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- New design has following attribute - extra relation, bi-directional\nAlso a list of tweets\n
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- The new API is follows(person) instead of add_follower(person)\nowynn = Person.new("Owynn")\nunclebob = persons[0].followers[1]\nowynn.follows(unclebob) instead of below\nunclebob.add_follower(owynn)\n
- abort transaction\nchange username and refresh in 2nd vm\nnot same as just returning cached instance in vm like other ORM&#x2019;s\n
- abort transaction\nchange username and refresh in 2nd vm\nnot same as just returning cached instance in vm like other ORM&#x2019;s\n
- abort transaction\nchange username and refresh in 2nd vm\nnot same as just returning cached instance in vm like other ORM&#x2019;s\n
- abort transaction\nchange username and refresh in 2nd vm\nnot same as just returning cached instance in vm like other ORM&#x2019;s\n
- abort transaction\nchange username and refresh in 2nd vm\nnot same as just returning cached instance in vm like other ORM&#x2019;s\n
- abort transaction\nchange username and refresh in 2nd vm\nnot same as just returning cached instance in vm like other ORM&#x2019;s\n
- abort transaction\nchange username and refresh in 2nd vm\nnot same as just returning cached instance in vm like other ORM&#x2019;s\n
- abort transaction\nchange username and refresh in 2nd vm\nnot same as just returning cached instance in vm like other ORM&#x2019;s\n
- abort transaction\nchange username and refresh in 2nd vm\nnot same as just returning cached instance in vm like other ORM&#x2019;s\n
- abort transaction\nchange username and refresh in 2nd vm\nnot same as just returning cached instance in vm like other ORM&#x2019;s\n
- abort transaction\nchange username and refresh in 2nd vm\nnot same as just returning cached instance in vm like other ORM&#x2019;s\n
- abort transaction\nchange username and refresh in 2nd vm\nnot same as just returning cached instance in vm like other ORM&#x2019;s\n
- abort transaction\nchange username and refresh in 2nd vm\nnot same as just returning cached instance in vm like other ORM&#x2019;s\n
- abort transaction\nchange username and refresh in 2nd vm\nnot same as just returning cached instance in vm like other ORM&#x2019;s\n
- abort transaction\nchange username and refresh in 2nd vm\nnot same as just returning cached instance in vm like other ORM&#x2019;s\n
- abort transaction\nchange username and refresh in 2nd vm\nnot same as just returning cached instance in vm like other ORM&#x2019;s\n
- abort transaction\nchange username and refresh in 2nd vm\nnot same as just returning cached instance in vm like other ORM&#x2019;s\n
- abort transaction\nchange username and refresh in 2nd vm\nnot same as just returning cached instance in vm like other ORM&#x2019;s\n
- abort transaction\nchange username and refresh in 2nd vm\nnot same as just returning cached instance in vm like other ORM&#x2019;s\n
- abort transaction\nchange username and refresh in 2nd vm\nnot same as just returning cached instance in vm like other ORM&#x2019;s\n
- abort transaction\nchange username and refresh in 2nd vm\nnot same as just returning cached instance in vm like other ORM&#x2019;s\n
- abort transaction\nchange username and refresh in 2nd vm\nnot same as just returning cached instance in vm like other ORM&#x2019;s\n
- abort transaction\nchange username and refresh in 2nd vm\nnot same as just returning cached instance in vm like other ORM&#x2019;s\n
- To understand the utility of read locks, imagine that you need to compute the average age of a large number of employees. While you are reading the employees and computing the average, another user changes an employee&#x2019;s age and commits (in the aftermath of the birthday party). You have now performed the computation using out-of-date information. You can prevent this frustration by read-locking the employees at the outset of your transaction; this prevents changes to those objects.\nNOTEIf you have a read lock on an object and you try to write that object, your attempt to commit that transaction will fail. \n
- To understand the utility of read locks, imagine that you need to compute the average age of a large number of employees. While you are reading the employees and computing the average, another user changes an employee&#x2019;s age and commits (in the aftermath of the birthday party). You have now performed the computation using out-of-date information. You can prevent this frustration by read-locking the employees at the outset of your transaction; this prevents changes to those objects.\nNOTEIf you have a read lock on an object and you try to write that object, your attempt to commit that transaction will fail. \n
- To understand the utility of read locks, imagine that you need to compute the average age of a large number of employees. While you are reading the employees and computing the average, another user changes an employee&#x2019;s age and commits (in the aftermath of the birthday party). You have now performed the computation using out-of-date information. You can prevent this frustration by read-locking the employees at the outset of your transaction; this prevents changes to those objects.\nNOTEIf you have a read lock on an object and you try to write that object, your attempt to commit that transaction will fail. \n
- Write locks are useful, for example, if you want to change the addresses of a number of employees. If you write-lock the employees at the outset of your transaction, you prevent other sessions from modifying one of the employees and committing before you can finish your work. This guarantees your ability to commit the changes.\n
- Write locks are useful, for example, if you want to change the addresses of a number of employees. If you write-lock the employees at the outset of your transaction, you prevent other sessions from modifying one of the employees and committing before you can finish your work. This guarantees your ability to commit the changes.\n
- Write locks are useful, for example, if you want to change the addresses of a number of employees. If you write-lock the employees at the outset of your transaction, you prevent other sessions from modifying one of the employees and committing before you can finish your work. This guarantees your ability to commit the changes.\n
- Write locks are useful, for example, if you want to change the addresses of a number of employees. If you write-lock the employees at the outset of your transaction, you prevent other sessions from modifying one of the employees and committing before you can finish your work. This guarantees your ability to commit the changes.\n
- create in one vm\nexecute in another vm\nhttp://maglev.github.com/docs/learn.html\n
- create in one vm\nexecute in another vm\nFull credit to Monty / GemStone - see URL\nhttp://maglev.github.com/docs/learn.html\n\nThreads cannot be persisted by reference (because the JIT may have have compile methods to machine code, which cannot be ported across VMs), but we can use a trick.\nWhat did we do here? Well, we started a thread and created a continuation. A continuation captures the state of a computation, effectively copying the stack at the point it was created (We can see in the inspection output that the continuation has a reference to a copy of the Thread that created it). We assign the continuation to a global variable for convenience, and then commit it to the Stone repository.\n\n
- create in one vm\nexecute in another vm\nFull credit to Monty / GemStone - see URL\nhttp://maglev.github.com/docs/learn.html\n
- abort transaction\nchange username and refresh in 2nd vm\nnot same as just returning cached instance in vm like other ORM&#x2019;s\n
- abort transaction\nchange username and refresh in 2nd vm\nnot same as just returning cached instance in vm like other ORM&#x2019;s\n
- abort transaction\nchange username and refresh in 2nd vm\nnot same as just returning cached instance in vm like other ORM&#x2019;s\n
- abort transaction\nchange username and refresh in 2nd vm\nnot same as just returning cached instance in vm like other ORM&#x2019;s\n
- abort transaction\nchange username and refresh in 2nd vm\nnot same as just returning cached instance in vm like other ORM&#x2019;s\n
- abort transaction\nchange username and refresh in 2nd vm\nnot same as just returning cached instance in vm like other ORM&#x2019;s\n
- abort transaction\nchange username and refresh in 2nd vm\nnot same as just returning cached instance in vm like other ORM&#x2019;s\n
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