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Quicksilver: Live Distributed Object

Quicksilver: Live Distributed Object. Siun-Wai Seow. Introduction Live Distributed Object Objective and Framework Quicksilver Multicast. Introduction.

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Quicksilver: Live Distributed Object

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  1. Quicksilver: Live Distributed Object Siun-Wai Seow

  2. Introduction • Live Distributed Object • Objective and Framework • Quicksilver Multicast

  3. Introduction • Modern integrated development environment (IDE) provides comprehensive tools (code editor, compiler/interpreter, runtime environment and debugger) that make software development seamless.

  4. Introduction • Framework for developing distributed applications face a more difficult challenge. • Especially for applications that require replication, scalable and fast response.

  5. Introduction • Researchers at Cornell University has been exploring ways to bridge the gap. • They created Live Distributed Objects.

  6. Live Distributed Objects • “Look and feel” of ordinary objects • Need not reside at a single location • Live = Real time.

  7. Objective of Live Object • From programmer’s perspective, live objects should fit easily into integrated environment such as .NET and J2EE. • From end-users’ perspective, they should be able to use live object as though it is a local object.

  8. Framework of Quicksilver System

  9. Functionality provided by a live object • Each object has an Internet-wide unique name and is registered in a global distributed “directory” resembling a DNS, where it can be located by the software components that wish to access it. • Live objects have “distributed” types. Among other things, type-checking helps verify that the communication “type” beneath an object matches the developer’s intent.

  10. Functionality provided by a live object • A live object provides a “natural” interface to its clients. An object representing a video stream would provide methods to send or receive video frames. An object that represents a replicated variable would provide get/set methods, etc.

  11. Functionality provided by a live object • Each object also has object-specific “logic” implementing some abstraction: a room, a medical record, a gossip-based overlay network, etc. This logic is translated into code that is deployed on and executed by the components accessing the live object. The protocols for replicating the object’s data among components and for multicasting events among them are provided by type-specific underlying “communication drivers”.

  12. Functionality provided by a live object • When a component tries to access a live object, an authentication and join protocol executes. This is used to enforce security, fetch the object’s “logic” from the distributed live objects directory, obtain a snapshot of the object’s state, initialize it etc. The object’s code maintains its state in response to event notifications.

  13. Multicast Protocols for Quicksilver • Quicksilver Scalable Multicast (QSM) • Quicksilver 2 (QS/2) • GO (Gossip Objects)

  14. Quicksilver Scalable Multicast (QSM) • Optimized to support large numbers of live objects that may represent streams of events, such as video channels, file backup folders, or stock price update notifications in a trading system.

  15. Quicksilver Scalable Multicast • IP Multicast • Hierarchy • Group Remapping • Repair Mechanism for Lost Packet

  16. Group Remapping

  17. Remapping and use IP Multicast

  18. Repair Mechanism for Packet Loss • The basic approach starts by constructing a logical token-ring that links the computers in the region. • Each token can work for multiple objects.

  19. Partition region into multiple token groups

  20. Protocol for inter/intra token groups

  21. Demo • http://www.cs.cornell.edu/projects/quicksilver/

  22. Programming • Programming with Live Distributed Objects, Krzysztof Ostrowski, Ken Birman, Danny Dolev, and Jong Hoon Ahnn

  23. Reference • Live Distributed Objects: Enabling the Active Web, Krzysztof Ostrowski, Ken Birman, Danny Dolev • Quicksilver Scalable Multicast, Krzysztof Ostrowski, Ken Birman, Danny Dolev

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