1 / 16

A Framework for Object-Based Event Composition in Distributed Systems

A Framework for Object-Based Event Composition in Distributed Systems. Peter Pietzuch and Brian Shand {Peter.Pietzuch,Brian.Shand}@cl.cam.ac.uk June 2002 – 12 th PhDOOS Workshop, Malaga, Spain. Motivation. Large-scale systems require new middleware paradigms

ameghan
Télécharger la présentation

A Framework for Object-Based Event Composition in Distributed Systems

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. A Framework for Object-Based Event Composition in Distributed Systems Peter Pietzuch and Brian Shand {Peter.Pietzuch,Brian.Shand}@cl.cam.ac.uk June 2002 – 12th PhDOOS Workshop, Malaga, Spain

  2. Motivation • Large-scale systems require new middleware paradigms • need: scalability, loose coupling of components, reliability • O-O middleware (request/reply) limitations: • synchronous, tight coupling, one-to-one communication • New m/w paradigm: Event-Based Communication • require additional, expressive middleware services • Framework for Composite Event Detection • handle complexity of many events • distributed composite event detection (scalability)

  3. Overview • Introduction to Event-Based Systems • Event-based Middleware Systems • Composite Event Detection • Our Composite Event (CE) Framework • Composite Event Language • Composite Event Objects • Mobile Detection Objects • Distributed Composite Event Detection • Future Work

  4. Event-based Systems publish notify • Notion of an Event: • Examples: PrinterFinishedEvent, SalesOrderEvent • Event Publishers publish events; Event Subscriber subscribe to events with a subscription (filter expression) Event Publisher Pub/Sub System Event Subscriber subscribe • asynchronous occurrence in time • contains data that describes the occurrence • can be implemented as an object

  5. Event-Based Middleware • Middleware using the Pub/Sub paradigm • built on top of an existing O-O/M-O middleware • Scalable and fault-tolerant event dissemination algorithms • Properties: • Must be able to: • integrate with O-O app programming language • handle large number of events • Publisher/Subscriber are decoupled • asynchronous notification • many-to-many communication  Composite Event Detection

  6. Management Plant A CED Plant B Supplier B Client A Sales Supplier A Plant C Department Composite Event Detection • Composite Events denote patterns of events • Composite Event Detectors • Example: “Client A submits new order” ; “Sales Dept. authorises order” ; “Plant A rejects order” • Scalability  Distributed detection

  7. Our CE Framework • Design Guidelines • Integration with an O-O middleware • Facilitate distributed detection • Little assumptions about pub&sub mechanisms • Components: • Composite Event Language • Composite Event Objects • Mobile Detection Objects

  8. Composite Event Language • Regular-expression based • can be detected by (extended) finite state automata • bounded resource usage • minimal set of operators • Examples • A followed by B, or C(A;B)|C • Any number of A inparallel with B<A*,B> • Distribution: • Decomposable alongsyntax tree • explicit input alphabet e.g. [A|B in A,B,C]

  9. Composite Event Objects • Represent composite events • Published by detectors • Example: (A|B);(C;D) • Interface to access primitive event instances

  10. Mobile Detection Objects • Detect composite events • Are Event Subscriber + Publisher • Encapsulate extended FSM with explicit input alphabet • Example: • Distribution: Agent-like behaviour • migrate to different location to optimise detection • can cooperate by decomposing expressions

  11. Distribution Example I • Example: new expression (A|B);(C;D) notify C;D A|B MDO MDO A|B C;D Composite Event A B Object (CEO) C D notify Mobile Detection notify MDO Object (MDO)

  12. Distribution Example II notify (A|B);(C;D) MDO (A|B);(C;D) notify C;D A|B MDO MDO A|B C;D Composite Event A B Object (CEO) C D notify Mobile Detection notify MDO Object (MDO)

  13. Distribution Example III

  14. Distributed Detection • Distribution Policy handles • MDO placement and migration (optimise for bandwidth, latency, …) • Degree of CE expression decomposition • Degree of replication (reliability and load-balancing) • Distribution Issues (Network delay) • Out of order arrival of events due to network delays • Best-Effort Detection vs. Guaranteed Detection • Event Publisher failure?

  15. Future Work • Implementation in Hermes Pub/Sub Simulator • investigate different Distribution Policies • performance/cost of the framework? • temporal issues… • Higher-level, domain-specific CE specification languages • user-friendly language • language-binding • GUI

  16. Conclusions • Event-Based Middleware • good for building large-scale systems • must provide additional services • Composite Event Detection • handle large number of events • should be part of the middleware • Framework for Distributed CE Detection • object-based (CEOs & MDOs) • distributed (CE detectors as agents) • composite event language (extended FSMs) • distribution policies

More Related