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Continuations And Java

Continuations And Java. Regis - xu.regis@gmail.com. Agenda. What is Continuations Why Continuations Implementations in Java Jetty Continuations API JavaFlow Kilim JVM Continuations. What is Continuations. Definition from wikipedia:

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Continuations And Java

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  1. Continuations And Java Regis - xu.regis@gmail.com

  2. Agenda • What is Continuations • Why Continuations • Implementations in Java • Jetty Continuations API • JavaFlow • Kilim • JVM Continuations

  3. What is Continuations • Definition from wikipedia: • Give a programming language the ability to save the execution state at any point and return to that point at alter point in the program • Basic characteristics: • Local data (variables, ...) is restored on successive calls. • Execution of a coroutine is only suspended when it yields, to be resumed when the coroutine is called again.

  4. started! 0 returned a continuation 1 returned another continuation

  5. Why Continuations • Thread is heavy and expensive • Writing asynchronous code in the synchronous style • Supporting functional languages • SAX parser • Web servers • linearize complex interactions • “back button” problem

  6. Implemented As Library • Jetty 6.0 • For resolving AJAX polling problem • Event based + retry

  7. Implemented As Library (Cont.) • Instrumentation byte code • Save current stack frames • Store local variables • Save PC • Restore stack trace • goto + switch table

  8. From A Thread of One’s Own

  9. Implemented As Library (Cont.) • Implementations • JavaFlow • Asymmetric coroutines: each yield needs to specify which coroutine should come next. • Kilim • Symmetric coroutines: a scheduler decides which coroutine should run next after a yield. • Framework has a thread pool and decide which coroutine run on which thread. • RIFE/Continuations (WebWork)

  10. Implemented In JVM • Support save and restore stack frames by JVM • No instrumentation needed • APIs is similar with library provided

  11. References • http://wiki.jvmlangsummit.com/JVM_Continuations • http://classparser.blogspot.com/2010/01/coroutines.html • http://lambda-the-ultimate.org/node/1002 • http://sourceforge.net/projects/jauvm/ • http://commons.apache.org/sandbox/javaflow/ • http://rifers.org/wiki/display/RIFECNT/Home • http://www.artima.com/lejava/articles/continuations.html • A Thread of One’s Own • Lazy Continuations for Java Virtual Machines

  12. Question?

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