Building Concurrent WebObjects applications with Scala
- 1. WebObjects + Scala Building Concurrent WebObjects applications with Scala Ravi Mendis
- 3. 2005 The year of Dual Core
- 6. 2010 Today
- 7. Entry-Level Cores Threads AMD Opteron 4 4 IBM Power7 4 16 Intel Xeon 4 8
- 8. High-End Cores Threads AMD Opteron 12 12 IBM Power7 8 32 Intel Xeon 6 12
- 10. Roadmap Cores Threads AMD Opteron 16 16 IBM Power7 ? ?? Intel Xeon 8 16
- 11. “By 2015 we will likely have over 100 cores on a many- core processing chip in our notebook computers.” - Computerworld
- 12. Welcome to the world of Multi-cores!
- 13. Q: How do we take advantage of multi-core processors?
- 15. #1 Threads & Locks
- 16. “Concurrency is hard. It involves a lot of problems that are very difficult to think about and reason about and understand” - Tim Bray co-inventor of XML
- 17. #1 Threads & Locks • HARD to program • HARD to scale • Contentious
- 18. java.lang.IllegalArgumentException: Cannot determine primary key for entity ASCCarveout from row: {charge = 3027.00; claimID = 321839138; } ! at com.webobjects.eoaccess.EODatabaseChannel._fetchObject(EODatabaseChannel.java:348) ! at com.webobjects.eoaccess.EODatabaseContext._objectsWithFetchSpecificationEditingContext (EODatabaseContext.java:3071) ! at com.webobjects.eoaccess.EODatabaseContext.objectsWithFetchSpecification(EODatabaseContext.java:3195) ! at com.webobjects.eocontrol.EOObjectStoreCoordinator.objectsWithFetchSpecification(EOObjectStoreCoordinator.java: 488) ! at com.webobjects.eocontrol.EOEditingContext.objectsWithFetchSpecification(EOEditingContext.java:4069) ...Deadlock! ! at er.extensions.eof.ERXEC.objectsWithFetchSpecification(ERXEC.java:1211) ! at com.webobjects.eoaccess.EODatabaseContext.objectsForSourceGlobalID(EODatabaseContext.java:4084) ! at com.webobjects.eocontrol.EOObjectStoreCoordinator.objectsForSourceGlobalID(EOObjectStoreCoordinator.java: 634) ! at com.webobjects.eocontrol.EOEditingContext.objectsForSourceGlobalID(EOEditingContext.java:3923) ! at er.extensions.eof.ERXEC.objectsForSourceGlobalID(ERXEC.java:1169) ! at com.webobjects.eoaccess.EODatabaseContext._fireArrayFault(EODatabaseContext.java:4245) ! at com.webobjects.eoaccess.EOAccessArrayFaultHandler.completeInitializationOfObject (EOAccessArrayFaultHandler.java:77) ! at com.webobjects.eocontrol._EOCheapCopyMutableArray.willRead(_EOCheapCopyMutableArray.java:37) ! at com.webobjects.eocontrol._EOCheapCopyMutableArray.count(_EOCheapCopyMutableArray.java:86) ! at com.mpv.evaluation.ClaimEvaluator.validateClaim(ClaimEvaluator.java:398) ! ...
- 19. BBC2, Top Gear - Series 15, Episode 1 - June 27 ’10
- 20. #2 Actor Model (A Share NOTHING Model)
- 21. Slowmation
- 22. Demo
- 23. html5 <video> <video poster="/slowmation/screenshots/0/2/4/425.jpg"> ! <source type="video/ogg" src="/slowmation/videos/6/d/8/423.ogg" /> ! <source type="video/mp4" src="/slowmation/videos/d/6/4/424.mp4" /> </video>
- 24. HTML5 Video Conversion Thumbnail (.jpg) Screenshot (.jpg) Video (.mp4) Video (.ogg)
- 25. Slowmation Actor (Video Processor) • actor ! THUMBNAIL • actor ! GRAB • actor ! CONVERT2H264 • actor ! CONVERT2OGG
- 26. !
- 27. Actor Messaging • Asynchronous • Non-blocking • Immutable Messages • NO shared data
- 28. Scala
- 29. Scala • Immutable/Mutable datatypes • Anonymous Functions (~Closures) • No Static variables and methods • Extensible
- 30. Scala val greeting: String = “Hello World”;
- 31. Scala val greeting = “Hello World”;
- 32. Scala val greeting = “Hello World”
- 33. Scala val greeting = “Hello World” // immutable var response = new String() // mutable response = “Hey!”
- 34. Java - Static Vars public class _Talent extends EOGenericRecord { public static final String ENTITY_NAME = "Talent"; }
- 35. Scala - Companion Object object Talent extends EOGenericRecord { val ENTITY_NAME = "Talent" }
- 36. Thread-Safe
- 37. Scala - Pattern Matching case a => { ... }
- 38. Scala - Pattern Matching try { var epi: EditPageInterface = D2W.factory.editPageForNewObjectWithEntityNamed(entityName, session) } catch { case e: IllegalArgumentException => { var epf: ErrorPageInterface = D2W.factory.errorPage(session) epf.setMessage(e.toString) } }
- 39. Scala - Case Classes case class PING case class PONG
- 40. Scala - Case Classes actor ! PING actor ! PONG
- 41. Scala - Case Classes case PING => { ... } case PONG => { ... }
- 42. Scala - Anonymous Functions x => x^2
- 43. Scala - Anonymous Functions x, y => x + y
- 44. Scala - Anonymous Functions x, y => {x + y}
- 45. Scala - Anonymous Functions case (PING => {...}) case (PONG => {...})
- 46. λ - Expressions
- 47. Scala Actors - Example case class THUMBNAIL(filepath: String) // Actor msg case class val processor = actor { loop { react() { case THUMBNAIL(filepath: String) => { ... } } } } // asynchronous processor ! THUMBNAIL(“/Library/WebServer/Documents/slowmation/screenshots/0/2/4/422.jpg”)
- 48. #2 Actor Model • EASY to program • Scalable • NO Deadlocks!
- 49. Q: Why can Scala be used with WebObjects?
- 50. A: Scala compiles to Java Byte-code
- 52. Why?
- 53. Performance • Exploit multi-core processors
- 54. Ajax • More responsive UI
- 55. How?
- 57. Java - Synchronize Static Variables private static String greeting = “Hello”; // private public void setGreeting(String aGreeting) { synchronized(greeting) { // synchronized block greeting = aGreeting; } }
- 58. Free!
- 59. WO - What is Shared? • Application • Session (concurrent WO)
- 60. Use ERXEC • Project Wonder • Automatic lock/unlock handling
- 62. Debugging
- 63. Demo
- 65. Bottlenecks
- 66. EOF - Bottleneck • Shared Object-cache • Antithesis to Share Nothing model • Uses single database connection • Single-Threaded
- 67. #3 STM (Software Transactional Memory)
- 68. EOF + Scala • DOESN’T work in Scala Actors! •
- 69. Solutions • Use Raw SQL • Alternative database access • Squeryl • ...
- 70. Squeryl
- 71. Demo
- 72. Squeryl • POSOs • Actor Compatible • Concurrent
- 73. “Scala as a concurrent programming language is powerful, safe and easy-to-use”
- 74. Benchmarks
- 75. The Test • ERWOAdaptor (Mina) • WO Worker as Actor • Apache bench • c = 5...65 • n = 500
- 76. Results
- 77. Time per req. (mean) 200 ms 150 ms 100 ms 50 ms 0 ms 5 10 15 20 25 30 35 40 45 50 55 60 65 WOAdaptor ERWOScalaAdaptor ERWOAdaptor
- 78. Requests per second 800 600 400 200 0 5 10 15 20 25 30 35 40 45 50 55 60 65 WOAdaptor ERWOScalaAdaptor ERWOAdaptor
- 79. “Scala as a concurrent programming language is powerful, safe and easy-to-use”
- 80. The R&D Imperative In life long love The key Is R&D The ladder of invention Has eternal slide extension Rung by rung You’ll climb to heaven above. Constant innovation Guarantees a satiation Of that ever changing want And deepening need Nourishment and care To think anew… Makes passions flair And lets a culture breed Between the sheets… - by Emma Ahmad
- 81. Q&A
- 82. References • What will YOU do with 100 cores? http://www.computerworld.com.au/article/354261/ • WebObjects with Scala http://wiki.objectstyle.org/confluence/display/WO/WebObjects+with+Scala • Case Study: Slowmation http://slowmation.uow.edu.au • Source: ERWOScalaAdaptor http://services.wocommunity.org/wowodc/ERWOScalaAdaptor