AmbientTalk: Object-oriented Event-driven programming in Mobile Ad hoc Networks

Transcription

1 AmbientTalk: Object-oriented Event-driven programming in Mobile Ad hoc Networks Tom Van Cutsem Stijn Mostinckx Elisa Gonzalez Boix Jessie Dedecker Wolfgang De Meuter Programming Technology Lab Vrije Universiteit Brussel Brussels, Belgium XXVI Intl. Conf. of the Chilean Computer Science Society, Iquique, Chile, Nov 2007

2 Context Object-oriented programming languages Hardware Software 2 Pervasive Computing (Mobile Networks)

3 Context Object-oriented programming languages Hardware Software 2 Pervasive Computing (Mobile Networks)

4 Mobile Ad hoc Networks 3

5 3 Mobile Ad hoc Networks Volatile Connections

6 3 Mobile Ad hoc Networks Scarce Infrastructure Volatile Connections

7 4 Loose Coupling Decoupling communication in Time & Synchronisation reduces impact of volatile connections

8 4 Loose Coupling Decoupling communication in Time & Synchronisation reduces impact of volatile connections

9 4 Loose Coupling Decoupling communication in Time & Synchronisation reduces impact of volatile connections asynchronous send

10 4 Loose Coupling Decoupling communication in Time & Synchronisation reduces impact of volatile connections

11 4 Loose Coupling Decoupling communication in Time & Synchronisation reduces impact of volatile connections

12 4 Loose Coupling Decoupling communication in Time & Synchronisation reduces impact of volatile connections

13 4 Loose Coupling Decoupling communication in Time & Synchronisation reduces impact of volatile connections asynchronous receive

14 5 Loose Coupling Decoupling communication in Space enables ad hoc anonymous collaborations

15 5 Loose Coupling Decoupling communication in Space enables ad hoc anonymous collaborations

16 5 Loose Coupling Decoupling communication in Space enables ad hoc anonymous collaborations provide service

17 5 Loose Coupling Decoupling communication in Space enables ad hoc anonymous collaborations provide service require service

18 6 Ubiquitous Flea Market Example: buy/sell concert tickets to proximate peers demand offer

19 6 Ubiquitous Flea Market Example: buy/sell concert tickets to proximate peers offer demand

20 7 AmbientTalk: the language Distributed object-oriented language Event-driven concurrency based on actors [Agha86] Future-type asynchronous message sends Built-in publish/subscribe engine for service discovery of remote objects

21 8 AmbientTalk: the project Started in 2005 Small team: 3-6 people Interpreter Pure Java implementation Runs on J2ME/CDC phones

22 9 Objects def Item := object: { def category; def description; def ownercontactinfo; def init(c,d,o) { category := c; description := d; ownercontactinfo := o; def getcontactinfo() { ownercontactinfo def placesupply() {... def placedemand() {... Prototype-based Objects are created: anonymously by cloning others def ticket := Item.new(ConcertTicket,...,... ); ticket.placedemand();

23 10 Extensible language def fac(n) { (n = 0).ifTrue: { 1 iffalse: { n * fac(n-1) Block closures Keyworded messages Interfacing with JVM

24 10 Extensible language def fac(n) { (n = 0).ifTrue: { 1 iffalse: { n * fac(n-1) Block closures Keyworded messages Interfacing with JVM def Button := jlobby.java.awt.button; def b := Button.new( test ); b.addactionlistener(object: { def actionperformed(ae) { println( button pressed ); );

25 11 Event loop concurrency Actor Based on E programming language [Miller05] Message queue Event loop

26 11 Event loop concurrency Actor Based on E programming language [Miller05] local object Message queue Event loop

27 11 Event loop concurrency Actor Based on E programming language [Miller05] local object obj.m() obj Message queue Event loop

28 11 Event loop concurrency Actor Based on E programming language [Miller05] local object remote object Message queue Event loop

29 11 Event loop concurrency Actor Based on E programming language [Miller05] local object remote object obj<-m() obj Message queue Event loop

30 11 Event loop concurrency Based on E programming language [Miller05] Actor local object remote object obj<-m() obj Message queue Event loop Actors cannot cause deadlock No race conditions on objects

31 12 Futures def future := advertisement<-getcontactinfo() advertisement

32 12 Futures def future := advertisement<-getcontactinfo() advertisement

33 12 Futures def future := advertisement<-getcontactinfo()? future advertisement

34 12 Futures def future := advertisement<-getcontactinfo()? future advertisement

35 12 Futures def future := advertisement<-getcontactinfo()? future advertisement

36 12 Futures def future := advertisement<-getcontactinfo()? future advertisement when: future becomes: { contactinfo println( contact seller: + contactinfo)

37 12 Futures def future := advertisement<-getcontactinfo()? future advertisement contactinfo when: future becomes: { contactinfo println( contact seller: + contactinfo)

38 12 Futures def future := advertisement<-getcontactinfo()? future advertisement contactinfo when: future becomes: { contactinfo println( contact seller: + contactinfo)

39 12 Futures def future := advertisement<-getcontactinfo()? future advertisement contactinfo when: future becomes: { contactinfo println( contact seller: + contactinfo)

40 13 Exporting objects item

41 13 Exporting objects deftype ConcertTicket; def Item := object: { def category; // a type tag... def placesupply() { export: item as: category; item

42 14 Service Discovery def placedemand() { whenever: category discovered: { item... <closure>

43 14 Service Discovery def placedemand() { whenever: category discovered: { item... <closure> item

44 14 Service Discovery def placedemand() { whenever: category discovered: { item... <closure> item

45 15 Failure handling item<-getcontactinfo() <closure> item

46 15 Failure handling item<-getcontactinfo() <closure> remote ref item

47 15 Failure handling item<-getcontactinfo() <closure> remote ref item

48 15 Failure handling item<-getcontactinfo() <closure> remote ref item

49 15 Failure handling item<-getcontactinfo() <closure> remote ref item when: item disconnected: { println( Item no longer available ) when: item reconnected: { println( Item available again )

50 15 Failure handling item<-getcontactinfo() <closure> remote ref item when: item disconnected: { println( Item no longer available ) when: item reconnected: { println( Item available again )

51 16 Events + Objects Block closures as first-class event-handlers preserve state (all lexically visible variables) can be arbitrarily nested Leads to less inversion of control whenever: category discovered: { item when: item<-getcontactinfo() becomes: { contactinfo println( contact seller: + contactinfo) when: item disconnected: { println( Item no longer available )

52 16 Events + Objects Block closures as first-class event-handlers preserve state (all lexically visible variables) can be arbitrarily nested Leads to less inversion of control whenever: category discovered: { item when: item<-getcontactinfo() becomes: { contactinfo println( contact seller: + contactinfo) when: item disconnected: { println( Item no longer available )

53 17 Conclusion MANETs loosely coupled collaboration Volatile Connections time & sync-decoupling Scarce Infrastructure space-decoupling AmbientTalk: event-driven OO language Buffered asynchronous messages: tolerate temporary network failures by default Built-in service discovery: no servers required