Resilient Partitioning of Pervasive Computing Services

Transcription

1 Resilient Partitioning of Pervasive Computing Services Engineer Bainomugisha Promotor: Prof. Dr. Wolfgang De Meuter Advisors: Jorge Vallejos Elisa Gonzalez Boix Programming Technology Lab Vrije Universiteit Brussel Brussels, Belgium Master Thesis, Defense 08 Sept. 2008

2 Pervasive Computing Environment Computational power is available everywhere (Weiser, 1993) User 2

3 Partitioning of Pervasive Computing Services Scenario: Hotel s Ambient Services Hotel room Laptop Hi-Fi system Ambient music player Guest music library 3

4 Partitioning of Pervasive Computing Services An application can be decomposed to run on multiple devices Ambient music player Hotel room music library Laptop Hi-Fi system Runtime Application Partitioning User Controlled Application Partitioning 4

5 Partitioning of Pervasive Computing Services Applications (whole or part) are not constrained to run on one device Ambient music player Hotel room Laptop music library Hi-Fi system Retractable Application Partitioning 5

6 Partitioning of Pervasive Computing Services Hotel room Laptop Hi-Fi system Ambient music player music library 6 Resilient to Network Failures

7 Resilient Service Partitioning Runtime Application Partitioning User Controlled Application Partitioning Retractable Application Partitioning Resilient to Network Failures 7

8 Survey of Related Work for Service Partitioning Runtime Partitioning Object-oriented partitioning User Controlled Retractable Resilient to Network Failures J-Orchestra (compilation) (programmer) Addistant (compilation) (programmer) JavaParty Doorastha (load-balancing) (runtime system) Component-oriented and agent-oriented partitioning Coign (compilation) (algorithm) AdJava (load-balancing) Hydra 8

9 Resilient Actor Model A resilient actor: is a modular encloses application functionality is active has its own thread of execution defines elastic bindings to other resilient actors 9

10 Resilient Actor Model A resilient actor: is a modular encloses application functionality is active has its own thread of execution defines elastic bindings to other resilient actors Two partitioning operations: Stretch: moves the resilient actor from one device to another Retract: moves the stretched actor back to original device 10

11 Resilient Actor Model A resilient actor: is a modular encloses application functionality is active has its own thread of execution defines elastic bindings to other resilient actors Two partitioning operations: Stretch: moves the resilient actor from one device to another Retract: moves the stretched actor back to original device Resilient Strategies: that specify different behaviors of the partitioning operations 11

12 Service Partitioning Ambient music player Objects Local references 12

13 Service Partitioning ambient music player Resilient actor Elastic binding music library Keyboard Local resources 13

14 Service Partitioning. ambient music player Hi-Fi system music library Stretch Keyboard 14

15 Manual Retraction. ambient music player Hi-Fi system music library Keyboard 15

16 Manual Retraction. ambient music player Hi-Fi system music library Retract Keyboard 16

17 Manual Retraction. ambient music player Hi-Fi system music library Keyboard 17

18 Automatic Retraction. ambient music player Hi-Fi system Retract music library Keyboard 18

19 Automatic Retraction. ambient music player Hi-Fi system music library Keyboard 19

20 Resilient Strategies. Stretch and Retract operations can have different implementations ambient music player Hi-Fi system [Rebind Strategy] [Copy Strategy] [Move Strategy] music library Keyboard [Standstill Strategy] 20

21 Resilient Strategies. Propagation: Partitioning operations proceed through elastic bindings ambient music player Hi-Fi system Stretch [Rebind Strategy] [Copy Strategy] [Move Strategy] music library Keyboard [Standstill Strategy] 21

22 Stretch Operation with Move Strategy. ambient music player Hi-Fi system [Move Strategy] music library Copy of Keyboard 22

23 Retract Operation with Move Strategy. ambient music player Hi-Fi system Retract [Move Strategy] music library Copy of Keyboard 23

24 After Retract Operation with Move Strategy. ambient music player Hi-Fi system [Move Strategy] music library Keyboard 24

25 Stretch Operation with Copy Strategy. ambient music player Laptop [Copy Strategy] Copy of music library music library [Move Strategy] Keyboard 25

26 Retract Operation with Copy Strategy. ambient music player Laptop Retract [Copy Strategy] Copy of music library music library [Move Strategy] Keyboard 26

27 After Retract Operation with Copy Strategy. ambient music player Laptop [Copy Strategy] music library [Move Strategy] Keyboard 27

28 Stretch Operation with Rebind Strategy. ambient music player Laptop [Rebind Strategy] music library Another resilient actor providing same service [Copy Strategy] [Move Strategy] Keyboard Keyboard 28

29 Retract Operation with Rebind Strategy. ambient music player Laptop Retract [Rebind Strategy] music library Another resilient actor providing same service [Copy Strategy] [Move Strategy] Keyboard Keyboard 29

30 After Retract Operation with Rebind Strategy. ambient music player Laptop [Rebind Strategy] music library Another resilient actor providing same service [Copy Strategy] [Move Strategy] Keyboard Keyboard 30

31 Resolution of Strategies Resilient strategies can be defined on resilient actors and elastic bindings ambient music player [Rebind Strategy] [Move Strategy] 31

32 Resolution of Strategies Resilient strategies can be defined on resilient actors and elastic bindings ambient music player Which resilient strategy will be applied? [Rebind Strategy] [Move Strategy] 32

33 Resolution of Strategies Resilient strategies can be defined on resilient actors and elastic bindings ambient music player Which resilient strategy will be applied? [Rebind Strategy] Resilient strategy on elastic binding standstill Resilient strategy on the resilient Actor {move, copy, rebind, standstill} rebind {move, copy, rebind, standstill} move {move, copy, rebind, standstill} [Move Strategy] copy {move, copy, rebind, standstill} 33

34 Resilient Actors in AmbientTalk AmbientTalk: Actor-based language for pervasive computing (Van Cutsem et. al, 2007) Mechanisms for handling network failures We extend AmbientTalk with four language constructs for resilient partitioning: actor: resilientas: and bindto: resilientas: stretch: and retract: 34

35 Resilient Actors in AmbientTalk (cont d) Implementation of the ambient music player using the resilient actor model ambientmusicplayer A Definition of a resilient actor def musiclibrary := actor: {.} resilientas: [copy]; def := actor: { } resilientas: [standstill]; B C musiclibrary def ambientmusicplayer := actor: { def thecontroller := bindto: resilientas: [move];. } resilientas: [standstill]; A def := actor: {, musiclibrary deftype musiclibraryservice; B def theaudio := bindto: resilientas: [standstill]; C def themusiclib := bindto: musiclibrary resilientas: [rebind(musiclibraryservice)]; } resilientas: [move]; 35

36 Resilient Actors in AmbientTalk (cont d) Implementation of the ambient music player using the resilient actor model ambientmusicplayer A Definition of a resilient actor def musiclibrary := actor: {.} resilientas: [copy]; def := actor: { } resilientas: [standstill]; B C musiclibrary def ambientmusicplayer := actor: { def thecontroller := bindto: resilientas: [move];. def cellphone := actor: {.}; } resilientas: [standstill]; A ambientmusicplayer <- stretch: cellphone; def := actor: {, musiclibrary deftype musiclibraryservice; def theaudio := bindto: resilientas: [standstill]; def themusiclib := bindto: musiclibrary resilientas: [rebind(musiclibraryservice)]; B C } resilientas: [move]; 36

37 Implementation of Resilient Actors Resilient Actor mirror Resilient actor s behavior Meta Level nil object Base Level Resilient actor s behavior mirror Resilient strategy Meta Level Base Level isolate object encapsulating behavior 37

38 Implementation of Elastic Binding mirror Strategy object Base Level Meta Level Resilient Actor 38

39 Extensible Implementation New Resilient Strategies by Extension e.g. Proactive state replication as an extension of the copy strategy def replicationstrategy := extend: copystrategy with: { def stretch: location { super^stretch: location; whenever: seconds(10) elapsed: { //update resilient actor state }; }; } 39

40 Requirements and Solution Revisited Runtime Application Partitioning Resilient Actors User Controlled Application Partitioning Stretch Operation Retractable Application Partitioning Retract Operation Resilient to Network Failures Automatic Retraction 40

41 Future Work Identifying more Resilient Strategies Context-Dependent Selection of Resilient Strategies Integration with Service Discovery Applying the resilient actor model to large pervasive applications 41

42 Conclusion Need for Resilient Partitioning of Pervasive Computing Services The Resilient Actor Model Resilient actors Elastic bindings Resilient strategies Extensible Implementation (Resilient Strategies) 42