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Session-Based Distributed Programming in Java: Theoretical Background and Implementation

This paper provides an overview of session programming in SJ, covering session types in object and process calculi, with examples and implementations discussed. It delves into theoretical background, related work, and future directions for session-based distributed programming.

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Session-Based Distributed Programming in Java: Theoretical Background and Implementation

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  1. Session-based Distributed Programming in Java Raymond Hu1, Nobuko Yoshida1 and Kohei Honda2 1. Imperial College London; 2. Queen Mary, Uni. of London February 2008

  2. Overview (1) • Background and Related Work. • Worked Example: Session Programming in SJ. • The SJ Session Runtime. • Conclusion and Future Work. Overview

  3. Session Types • Type systems for process calculi: • Takeuchi et al. An Interaction-based Language and its Typing System. (1994) • Honda et al. Language Primitives and Type Discipline for Structured Comm… (1998) • Gay and Hole. Subtyping for Session Types in the Pi Calculus. (1999) • Hole and Gay. Bounded Polymorphism in Session Types. (2003) Theoretical Background

  4. Session Types • Type systems for process calculi: • Takeuchi et al. An Interaction-based Language and its Typing System. (1994) • Honda et al. Language Primitives and Type Discipline for Structured Comm… (1998) • Gay and Hole. Subtyping for Session Types in the Pi Calculus. (1999) • Hole and Gay. Bounded Polymorphism in Session Types. (2003) • Session types for object calculi: • Dezani-Ciancaglini et al. A distributed Object-oriented Language with Session... (2005) • Dezani-Ciancaglini et al. Session Types for Object-oriented Languages. (2006) • Dezani-Ciancaglini et al. Bounded Session Types for Object-oriented Languages. (2007) • Coppo et al. Asynchronous Session Types and Progress for Object-oriented... (2007) Theoretical Background

  5. Session Types • Type systems for process calculi: • Takeuchi et al. An Interaction-based Language and its Typing System. (1994) • Honda et al. Language Primitives and Type Discipline for Structured Comm… (1998) • Gay and Hole. Subtyping for Session Types in the Pi Calculus. (1999) • Hole and Gay. Bounded Polymorphism in Session Types. (2003) • Session types for object calculi: • Dezani-Ciancaglini et al. A distributed Object-oriented Language with Session... (2005) • Dezani-Ciancaglini et al. Session Types for Object-oriented Languages. (2006) • Dezani-Ciancaglini et al. Bounded Session Types for Object-oriented Languages. (2007) • Coppo et al. Asynchronous Session Types and Progress for Object-oriented... (2007) • Implementation of a practical and distributed language. Theoretical Background

  6. Implementation of Session Types • Singularity OS [FAHHHLL06]: • Restrictions on session features, not distributed. Related Work

  7. Implementation of Session Types • Singularity OS [FAHHHLL06]: • Restrictions on session features, not distributed. • Multithreaded functional language design [VGR06]: • Not distributed, no actual implementation. Related Work

  8. Implementation of Session Types • Singularity OS [FAHHHLL06]: • Restrictions on session features, not distributed. • Multithreaded functional language design [VGR06]: • Not distributed, no actual implementation. • Encodings of sess. types (e.g. Haskell [NT04], C++): • Demonstrate S.T. ideas, but not full implementations. Related Work

  9. Implementation of Session Types • Singularity OS [FAHHHLL06]: • Restrictions on session features, not distributed. • Multithreaded functional language design [VGR06]: • Not distributed, no actual implementation. • Encodings of sess. types (e.g. Haskell [NT04], C++): • Demonstrate S.T. ideas, but not full implementations. • Why use “untyped” sockets if we can use sessions? Related Work

  10. Overview (2) • Background and Related Work. • Worked Example: Session Programming in SJ. • The SJ Session Runtime. • Conclusion and Future Work. Overview

  11. An Online Ticket Ordering System Worked Example: Session Programming in SJ

  12. begin Protocol Specification (1) Worked Example: Session Programming in SJ

  13. begin. !(String) Protocol Specification (1) Worked Example: Session Programming in SJ

  14. begin. !(String). ?(Double) Protocol Specification (1) Worked Example: Session Programming in SJ

  15. begin. !(String). ?(Double) Protocol Specification (1) ![ ]*. … Worked Example: Session Programming in SJ

  16. begin. ?[ ?(String). !(Double) ]*. … begin. !(String). ?(Double) Protocol Specification (1) ![ ]*. … Worked Example: Session Programming in SJ

  17. Protocol Specification (2) … ?{ }. … Worked Example: Session Programming in SJ

  18. Protocol Specification (2) … ACCEPT: … , REJECT: … ?{ }. … Worked Example: Session Programming in SJ

  19. Protocol Specification (3) protocol p_as { } Worked Example: Session Programming in SJ

  20. Protocol Specification (3) protocol p_as { } begin. !( ) Worked Example: Session Programming in SJ

  21. Protocol Specification (3) ?(Address).!(Date) protocol p_as { } begin. !( ) Worked Example: Session Programming in SJ

  22. protocolp_ca{ begin. ![ !(String). ?(Double) ]*. … // Customer SJSocket s_ca = SJSocketImpl.create(p_ca); Protocol Implementation (1) Worked Example: Session Programming in SJ

  23. protocolp_ca{ begin. ![ !(String). ?(Double) ]*. … // Customer SJSocket s_ca = SJSocketImpl.create(p_ca); s_ca.request(Agency, port); Protocol Implementation (1) Worked Example: Session Programming in SJ

  24. protocolp_ca{ begin. ![ !(String). ?(Double) ]*. … // Customer SJSocket s_ca = SJSocketImpl.create(p_ca); s_ca.request(Agency, port); Protocol Implementation (1) s_ca.outwhile(!decided){ } Worked Example: Session Programming in SJ

  25. protocolp_ca{ begin. ![ !(String). ?(Double) ]*. … // Customer SJSocket s_ca = SJSocketImpl.create(p_ca); s_ca.request(Agency, port); s_ca.send(travDetails); Protocol Implementation (1) s_ca.outwhile(!decided){ } Worked Example: Session Programming in SJ

  26. protocolp_ca{ begin. ![ !(String). ?(Double) ]*. … // Customer SJSocket s_ca = SJSocketImpl.create(p_ca); s_ca.request(Agency, port); s_ca.send(travDetails); cost = (Double)s_ca.receive(); decided = …; Protocol Implementation (1) s_ca.outwhile(!decided){ } Worked Example: Session Programming in SJ

  27. protocolp_ca{ begin. ![ !(String). ?(Double) ]*. … // Customer SJSocket s_ca = SJSocketImpl.create(p_ca); s_ca.request(Agency, port); s_ca.send(travDetails); decided = …; Protocol Implementation (1) s_ca.outwhile(!decided){ } cost = s_ca.receive(); Worked Example: Session Programming in SJ

  28. … !{ ACCEPT: … , // 1 REJECT: … // 2 } … // Customer s_ca.select(ACCEPT){ … // 1 } Protocol Implementation (2) Worked Example: Session Programming in SJ

  29. … !{ ACCEPT: … , // 1 REJECT: … // 2 } … // Customer s_ca.select(ACCEPT){ … // 1 } Protocol Implementation (2) if(cost < 100.00){ } else{ } Worked Example: Session Programming in SJ

  30. … !{ ACCEPT: … , // 1 REJECT: … // 2 } … // Customer s_ca.select(ACCEPT){ … // 1 } s_ca.select(REJECT){ …// 2 } Protocol Implementation (2) if(cost < 100.00){ } else{ } Worked Example: Session Programming in SJ

  31. … ?{ ACCEPT: … , // 1’ REJECT: … // 2’ } … // Agency Protocol Implementation (3) … s_ac.branch(){ } Worked Example: Session Programming in SJ

  32. … ?{ ACCEPT: … , // 1’ REJECT: … // 2’ } … // Agency case ACCEPT: { … // 1’ } case REJECT: { … // 2’ } Protocol Implementation (3) … s_ac.branch(){ } Worked Example: Session Programming in SJ

  33. Putting Customer Together protocol p_ca{…} Worked Example: Session Programming in SJ

  34. Putting Customer Together protocol p_ca{…} SJSocket s_ca = SJSocketImpl.create(p_ca); Worked Example: Session Programming in SJ

  35. Putting Customer Together protocol p_ca{…} SJSocket s_ca = SJSocketImpl.create(p_ca); s_ca.request(Agency, port); s_ca.outwhile(…){ … } … Worked Example: Session Programming in SJ

  36. Putting Customer Together protocol p_ca{…} SJSocket s_ca = SJSocketImpl.create(p_ca); s_ca.request(Agency, port); s_ca.outwhile(…){ … } … try(s_ca){ } Worked Example: Session Programming in SJ

  37. Putting Customer Together protocol p_ca{…} SJSocket s_ca = SJSocketImpl.create(p_ca); s_ca.request(Agency, port); s_ca.outwhile(…){ … } … catch(SJIOException ioe){ … } try(s_ca){ } Worked Example: Session Programming in SJ

  38. Putting Customer Together protocol p_ca{…} SJSocket s_ca = SJSocketImpl.create(p_ca); s_ca.request(Agency, port); s_ca.outwhile(…){ … } … catch(SJIncompatibleSessionException ise){ … } catch(SJIOException ioe){ … } try(s_ca){ } Worked Example: Session Programming in SJ

  39. Putting Customer Together protocol p_ca{…} SJSocket s_ca = SJSocketImpl.create(p_ca); s_ca.request(Agency, port); s_ca.outwhile(…){ … } … catch(SJIncompatibleSessionException ise){ … } catch(SJIOException ioe){ … } finally{ … // Session socket ‘s_ca’ is closed. } try(s_ca){ } Worked Example: Session Programming in SJ

  40. Overview (3) • Background and Related Work. • Worked Example: Session Programming in SJ • The SJ Session Runtime. • Conclusion and Future Work. Overview

  41. General Framework The SJ Session Runtime

  42. Session Runtime Architecture

  43. Sessions over TCP (1) • Map session operations to Socket communications. • Distributed interaction. • Preserve asynchrony. The SJ Session Runtime

  44. Session Initiation (1) The SJ Session Runtime

  45. Session Initiation (2) • C → A : Type of session expected by C. • | A → C : Type of session expected by A. The SJ Session Runtime

  46. Basic Message Passing The SJ Session Runtime

  47. Sessions over TCP (2) • Map session operations to Socket communications. • Distributed communication. • Preserve asynchrony. • Interesting case is delegation. The SJ Session Runtime

  48. “Lost Messages” (1) The SJ Session Runtime

  49. “Lost Messages” (2) The SJ Session Runtime

  50. Sessions over TCP (3) • Map session operations to Socket communications. • Distributed communication. • Preserve asynchrony. • Interesting case is delegation. • Possible designs: • Indefinite forwarding (cf. MobileIP). The SJ Session Runtime

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