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 Programming Technology Lab Vrije Universiteit Brussel Brussels, Belgium LAMP - EPFL, July 25th 2007, Lausanne

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 Intermittent Connectivity

6 3 Mobile Ad hoc Networks Scarce Infrastructure Intermittent Connectivity

7 4 Loose Coupling [Eugster et al. 03] Decoupling communication in Time & Synchronisation reduces impact of volatile connections

8 4 Loose Coupling [Eugster et al. 03] Decoupling communication in Time & Synchronisation reduces impact of volatile connections

9 4 Loose Coupling [Eugster et al. 03] Decoupling communication in Time & Synchronisation reduces impact of volatile connections asynchronous send

10 4 Loose Coupling [Eugster et al. 03] Decoupling communication in Time & Synchronisation reduces impact of volatile connections

11 4 Loose Coupling [Eugster et al. 03] Decoupling communication in Time & Synchronisation reduces impact of volatile connections

12 4 Loose Coupling [Eugster et al. 03] Decoupling communication in Time & Synchronisation reduces impact of volatile connections

13 4 Loose Coupling [Eugster et al. 03] 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 Example: music player 6

19 Example: music player 6

20 Example: music player 6

21 6 Example: music player 32% 21%

22 7 AmbientTalk: the language Distributed prototype-based 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

23 8 AmbientTalk: the project Started in 2005 Small team: 3-6 people Interpreter (not optimised) Pure Java implementation Runs on J2ME/CDC phones

24 9 Objects def Window := object: { def title := Untitled ; def init(t) { title := t; super := ClosedWindow; def show() { super := OpenWindow; Prototypes Delegation Trait composition First-class delegation def OpenWindow := object: { def draw() {... def ClosedWindow := object: { def draw() {... def w := Window.new( Test ); w.draw();

25 10 Extensible language def fac(n) { if: (n = 0) then: { 1 else: { n * fac(n-1)

26 10 Extensible language def fac(n) { if: (n = 0) then: { 1 else: { n * fac(n-1) def Button := jlobby.java.awt.button; def b := Button.new( test ); b.addactionlistener(object: { def actionperformed(ae) { system.println( button pressed ); );

27 10 Extensible language def fac(n) { if: (n = 0) then: { 1 else: { n * fac(n-1) Block closures Keyworded messages Interfacing with JVM Reflection def Button := jlobby.java.awt.button; def b := Button.new( test ); b.addactionlistener(object: { def actionperformed(ae) { system.println( button pressed ); );

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

29 11 Event loop concurrency Actor Based on E programming language [Miller05] local object Message queue Event loop

30 11 Event loop concurrency Actor Based on E programming language [Miller05] local object obj.m() obj Message queue Event loop

31 11 Event loop concurrency Actor Based on E programming language [Miller05] local object remote object Message queue Event loop

32 11 Event loop concurrency Actor Based on E programming language [Miller05] local object remote object obj<-m() obj Message queue Event loop

33 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

34 12 Futures def future := mplayer<-numsongsinlibrary() mplayer

35 12 Futures def future := mplayer<-numsongsinlibrary() mplayer

36 12 Futures def future := mplayer<-numsongsinlibrary()? future mplayer

37 12 Futures def future := mplayer<-numsongsinlibrary()? future mplayer

38 12 Futures def future := mplayer<-numsongsinlibrary()? future mplayer

39 12 Futures def future := mplayer<-numsongsinlibrary()? future mplayer when: future becomes: { num system.println( user shares + num + songs. )

40 12 Futures def future := mplayer<-numsongsinlibrary()? future mplayer num when: future becomes: { num system.println( user shares + num + songs. )

41 13 Exporting objects deftype MusicPlayer; def interface := object: { def opensession() {... interface export: interface as: MusicPlayer;

42 13 Exporting objects deftype MusicPlayer; def interface := object: { def opensession() {... interface export: interface as: MusicPlayer;

43 14 Ambient References def mplayerfuture := ambient: MusicPlayer; Initiates service discovery Immediately returns future for object to be discovered

44 14 Ambient References def mplayerfuture := ambient: MusicPlayer;? mplayer Future Initiates service discovery Immediately returns future for object to be discovered

45 15 Ambient References def mplayerfuture := ambient: MusicPlayer; mplayer Future?

46 15 Ambient References def mplayerfuture := ambient: MusicPlayer; def sessionfuture := mplayerfuture<-opensession(); mplayer Future?

47 15 Ambient References def mplayerfuture := ambient: MusicPlayer; def sessionfuture := mplayerfuture<-opensession(); mplayer Future?

48 15 Ambient References def mplayerfuture := ambient: MusicPlayer; def sessionfuture := mplayerfuture<-opensession(); mplayer Future? when: mplayerfuture becomes: { ambientref println( music player found )

49 15 Ambient References def mplayerfuture := ambient: MusicPlayer; def sessionfuture := mplayerfuture<-opensession(); mplayer Future? interface when: mplayerfuture becomes: { ambientref println( music player found )

50 15 Ambient References def mplayerfuture := ambient: MusicPlayer; def sessionfuture := mplayerfuture<-opensession(); mplayer Future? interface ambientref when: mplayerfuture becomes: { ambientref println( music player found )

51 15 Ambient References def mplayerfuture := ambient: MusicPlayer; def sessionfuture := mplayerfuture<-opensession(); mplayer Future? interface ambientref when: mplayerfuture becomes: { ambientref println( music player found )

52 15 Ambient References def mplayerfuture := ambient: MusicPlayer; def sessionfuture := mplayerfuture<-opensession(); mplayer Future? interface ambientref when: mplayerfuture becomes: { ambientref println( music player found )

53 15 Ambient References def mplayerfuture := ambient: MusicPlayer; def sessionfuture := mplayerfuture<-opensession(); mplayer Future? interface ambientref Bound Unbound Connected Disconnected

54 16 Failure handling Event handlers on ambient references: mplayer Future? interface ambientref when: ambientref disconnects: { println( music player disconnected ) when: ambientref reconnects: { println( music player reconnected )

55 16 Failure handling Event handlers on ambient references: mplayer Future? interface ambientref when: ambientref disconnects: { println( music player disconnected ) when: ambientref reconnects: { println( music player reconnected )

56 16 Failure handling Event handlers on ambient references: mplayer Future? interface ambientref when: ambientref disconnects: { println( music player disconnected ) when: ambientref reconnects: { println( music player reconnected )

57 17 Failure Handling Leased references which eventually expire Futures + timeouts when: o<-m()@timeout(minutes(10)) becomes: { v // process return value catch: TimeoutException using: { e // deal with timeout

58 18 Variations Past experiments: ambient omni -references: broadcasting content-based discovery Future experiments: Customisable message delivery guarantees First-class proximity: restrict spatial scope of ambient references

59 19 Lessons Learned AmbientTalk = OO + Events: Block closures as nested event handlers Futures: non-blocking synchronisation Buffered asynchronous messaging abstracts over intermittent connectivity Ambient references: space-decoupled remote object references

60 20 Conclusion MANETs: loosely coupled collaboration AmbientTalk: actor-based OO language Deal with universal MANET characteristics at the language level: Intermittent Connectivity: time & sync-decoupled references Scarce Infrastructure: space-decoupled references