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QoS Enhanced Middleware

QoS Enhanced Middleware. Jürgen Dittrich & Marcin Solarski (GMD Fokus). Middleware: Shields Developer from underlying Technology changes Clear description of Customer/Provider interfaces Functional interfaces typically described in OMG/IDL OMG CORBA focused on QoS bindings with IIOP/TCP

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QoS Enhanced Middleware

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  1. QoS Enhanced Middleware Jürgen Dittrich & Marcin Solarski (GMD Fokus)

  2. Middleware: • Shields Developer from underlying Technology changes • Clear description of Customer/Provider interfaces • Functional interfaces typically described in OMG/IDL • OMG CORBA focused on QoS bindings with IIOP/TCP • Open issue: Expressing QoS req’s & Map them on bindings • Extended Object Bindings (UDP, LRMP, RSVP) • Extended Object Implementations (Replications)? • Example Application: Jonathan based Online Auction • Expressing QoS Req’s: Quality Modeling Language (QML, HP Labs) • Mapping QML on Extended DOT (bindings&impl’s)

  3. Quality Modeling Language (QML, HP labs) • Specification of QoS requirements • Related to ISO concepts • Declarative language related/similar to OMG UML/IDL • Language constructs: • contract type (QoS category: performance, availability, ..) • type AuctionPerformance = contract • { • response_time : decreasing numeric msec; • failure_rate : decreasing numeric no/sec; • }; • contracts (independent from functional IDL interface) • profile (associates contracts and IDL interfaces)

  4. Quality Modeling Language (QML, HP labs) • Relationships of QML constructs

  5. Quality Modeling Language (QML, HP labs) • QML in Middleware

  6. Modular ORB and QoS Agents • QoS Agent maps & negotiates QoS requirements/offers • Part of object binding Provided QoS Requested QoS server client QoS mapping Binding (inter-object protocol, ...) QoS on creation bindingfactory

  7. Dutch Flower Auction in Aalsmeer/NL

  8. Computational View of Online Dutch Auction Dealer 2. bid(); Multicast binding Mediator Dealer 1. offer(); Dealer

  9. Example Application:Jonathan based Online Auction

  10. Some QoS Requirements of the Dutch auction system • Reliability • Reliable communication channels • Scalability • Hunderts of dealers • All dealers need the same QoS of the communication. • Availability • The mediator has to be functional during the whole auction. • Mediator crashes have to be tolerated

  11. Solution mechanisms • Reliability • light-weight reliable multicast channel (LRMP) • reliable pt-to-pt channel for back channel (IIOP) • Scalability • Level-based architecture for mediators • Availability • Mediator Replication

  12. Choice of the QoS attribute on the example of the replication mechanism • Replication scheme • Active • high availability • replica implementation determinism • Passive • lower availability • No determinism requirement • Hybrids • semi-active, etc. • How to automate the choice the right mech? • QoS mapping

  13. Conclusions • Specification of QoS in QML • QoS Mapping/Translation & Tuning w/ QoS Agents • QoS Enhanced bindings build upon Modular ORB/Middlew. • QoS Enhanced bindings encompass communication and execution aspects • Online Auction for Evaluation of QoS Enhanced Middleware

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