1 / 37

Dynamic and Selective Combination of Extension in Component-based Applications

Dynamic and Selective Combination of Extension in Component-based Applications Eddy Truyen, Bart Vanhaute, Wouter Joosen, Pierre Verbaeten, Bo N. Jørgensen Outline Motivation: Dynamic customization of distributed services Overview of wrapper-based model Lasagne

paul
Download Presentation

Dynamic and Selective Combination of Extension in Component-based Applications

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. Dynamic and Selective Combination of Extension in Component-based Applications Eddy Truyen, Bart Vanhaute, Wouter Joosen, Pierre Verbaeten, Bo N. Jørgensen

  2. Outline • Motivation: Dynamic customization of distributed services • Overview of wrapper-based model Lasagne • Problem statement: analysis of problems with wrappers • Detailed overview of Lasagne • Lessons learned • Conclusion

  3. Motivation • Support for dynamic and client-specific customization of distributed services is needed • An example: web service on the Internet • Multiple clients are accessing service instance simultaneously • Different clients have different customization needs • One client must be able to customize the web service for use in its own context, • without affecting other clients (service behavior delivered to other clients must not be affected)

  4. Motivation (ctd) • Customization process = context-sensitive and dynamic combination of extensions to a minimal core system • Extensions can be functional (e.g. refined core service) and non-functional (e.g authentication, authorization) • Revisiting example: web service on the Internet • Each client must be able to select a subset of extensions into the core service • for use in its own context: • per client request, per client session • without interfering with other clients

  5. Short overview of Lasagne • A programming, deployment and run-time model that supports dynamic combination of extensions per client request • Inspired by wrapper-based design patterns • Decorator and Role Object • Advantages of wrappers • already support combination of extensions to a component • operate at instance-level => customization of online services • Deal with disadvantages of wrappers • object identity problems

  6. Agenda Decorator 2 Decorator 1 Decorator 1 Decorator 2 Wrapper-based design patterns • Decorator [Gamma et al] • Disjunctive chaining supports selective combination

  7. Role 2 Role 1 Wrapper-based design patterns • Role Object [Baumer et al] • Component type widening • Dynamically adds new service interface • selection of roles by means of specification object Component getRole(specification)

  8. Problem Statement System-wide interaction refinement

  9. DatingSystem Agenda Authoriz. Check Wrapper Authoriz. Check Wrapper AccessDenied Exception Handler AccessDenied Exception Handler Group App. Service Group App. Service Object Identity Problem Atomic Agenda Atomic Agenda Spaghetti Problem

  10. DatingSystem Agenda Authoriz. Check Wrapper Authoriz. Check Wrapper AccessDenied Exception Handler AccessDenied Exception Handler Group App. Service Group App. Service Object Identity Problem Atomic Agenda Atomic Agenda Spaghetti Problem

  11. DatingSystem Agenda Authoriz. Check Wrapper Authoriz. Check Wrapper AccessDenied Exception Handler AccessDenied Exception Handler Group App. Service Group App. Service Object Identity Problem Atomic Agenda Atomic Agenda Spaghetti Problem

  12. DatingSystem Agenda Authoriz. Check Wrapper Authoriz. Check Wrapper authorization & access control AccessDenied Exception Handler AccessDenied Exception Handler Group App. Service Group App. Service Object Identity Problem Atomic Agenda Atomic Agenda Spaghetti Problem

  13. DatingSystem Agenda Authoriz. Check Wrapper Authoriz. Check Wrapper authorization & access control AccessDenied Exception Handler AccessDenied Exception Handler Group App. Service Group App. Service Object Identity Problem Atomic Agenda Atomic Agenda Spaghetti Problem

  14. DatingSystem Agenda Authoriz. Check Wrapper Authoriz. Check Wrapper AccessDenied Exception Handler AccessDenied Exception Handler Group App. Service Group App. Service Atomic Agenda Atomic Agenda Coordination Problem

  15. DatingSystem Agenda Authoriz. Check Wrapper Authoriz. Check Wrapper AccessDenied Exception Handler AccessDenied Exception Handler Group App. Service Group App. Service Inconsistency Atomic Agenda Atomic Agenda Coordination Problem

  16. DatingSystem Agenda Authoriz. Check Wrapper Authoriz. Check Wrapper AccessDenied Exception Handler AccessDenied Exception Handler Group App. Service Group App. Service Calling context must be propagated over entire core system Atomic Agenda Atomic Agenda Coordination Problem

  17. DatingSystem Agenda Authoriz. Check Wrapper Authoriz. Check Wrapper AccessDenied Exception Handler AccessDenied Exception Handler Group App. Service Group App. Service Calling context must be propagated over entire core system Atomic Agenda Atomic Agenda Coordination Problem

  18. DatingSystem Agenda Authoriz. Check Wrapper Authoriz. Check Wrapper AccessDenied Exception Handler AccessDenied Exception Handler Group App. Service Group App. Service Contextual change must be propagated over entire core system Atomic Agenda Atomic Agenda Coordination Problem

  19. Other problems solved • Partial ordering constraints between wrappers • Some wrapper composition logic should not be under control of the clients • Use of design patterns must be anticipated by core application developer. • Technical problems • Problems with delegation and common self • State consistency between multiple instances of the same wrapper definition

  20. Turning Spaghetti into Lasagne • Externalize wrapper composition logic from the code of core system and extensions • Clients can customize the wrapper composition logic on a per collaboration basis

  21. Agenda 2 DatingSystem Agenda 1 collaboration High-level overview of Lasagne • Introductory terms • Component-based, distributed core system • Component type =< {services}, {dependencies}> • Connection supported by COTS middleware • Client request initiates collaboration between core components • Lasagne customization process consists of three phases: extension programming, deployment of extensions to a core system, and selective combination per collaboration connection dependency service

  22. Group App. Service Atomic Agenda High-level overview of Lasagne • The extension programming model • An extensions is implemented as layer of wrappers • Wrappers are programmed in hybrid form between Decorator and Role Object • Each wrapper definition is meant for decorating a specific minimalcomponent type <{Dating}, {Negotiation}> <{Negotiation}, {}> *

  23. High-level overview of Lasagne • Deployment of extensions to core application • Declarative specification of how to integrate wrappers to a specific core application • specify fine-grained partial ordering constraints

  24. Authoriz. Check Wrapper AccessDenied Exception Handler :Agenda :DatingSystem Group App. Service dynamic adjustment of message flow through appropriate chain of wrappers Atomic Agenda High-level overview of Lasagne • Selective combination per client request

  25. Lasagne Concepts • Component Identity • Aggregates core instance and its wrappers into one identity • Removes the spaghetti of wrapper references • Extension Identifier • qualified name that uniquely identifies an extension • Is used to designate wrappers as belonging to a specific extension • Composition Policy {…} • specifies the subset of extension identifiers for a specific collaboration between client and core system • A composition policy propagates with the collaboration flow

  26. Lasagne concepts • Contextual properties • e.g client-specific preferences, message flow history • defined as <name, value> pairs that propagate with the collaboration flow • Interceptors • define contextual properties of collaboration • select or unselect extensions. Typical selection rule: • If <condition> is satisfied within <context> thenattach/discard <extension identifier> to composition policy • Variation point • Extension to runtime component model • Generic message dispatch mechanism • Dynamically constructs wrapper chain • Interprets composition policy and ordering constraints

  27. Agenda 2 DatingSystem Agenda 1 authorization & access control Component Identity

  28. Agenda 2 DatingSystem Agenda 1 authorization & access control Extension Identifiers <“group”> <“authoriz”>

  29. add <“authoriz”> Agenda 2 DatingSystem Agenda 1 authorization & access control Interceptors and Composition Policy {<“authoriz”>} { } <“group”> {<“authoriz”>} <“authoriz”> { } {<“authoriz”>} Interceptor definitions Attach client_localhost, client_identity as contextual properties to collaboration. Ifclient_localhoston remote subnet then attach <“authoriz”>to composition policy

  30. add <“authoriz”> Agenda 2 DatingSystem Agenda 1 authorization & access control Underlying runtime mechanisms {<“authoriz”>} <“group”> {<“authoriz”>} <“authoriz”> { } {<“authoriz”>} • Propagation of composition policy • Propagation of contextual properties • Variationpoint performs automatic adjustment of message flow

  31. Lessons learned • Lasagne is suitable for customization at the coarse-grained architectural level • Extensions are reusable over multiple applications • is supported in Java implementation of Lasagne (co-work with Renaud Pawlak) • Wrappers are reusable over different types of components • Deployment-time operation that dynamically connects extension operation to core operation.

  32. Lessons Learned (ctd) • Lasagne is too low-level and complex to use • Need to build higher-level tool or language on top of Lasagne framework • feedback from advanced separation of concerns community • Aspect-oriented programming • Aspectual Components • GenVoca and Mixin layers • Multidimensional separation of concerns

  33. Conclusion • Customization of distributed services • non-invasive customization • dynamic combination of system-wide extensions • consistency and scalability • context-sensitiveness • simultaneous client-specific views • message flow history • Lasagne prototypes • Programming Languages with an open implementation • Correlate, Java • Reflective middleware platforms • Java RMI, Lasagne ORB

  34. Other problems solved • Partial ordering constraints between wrappers • Multiple instances of the same wrapper definition due disjunctive wrapper chains • difficult to keep the states of different wrapper instances consistent to each other • No Delegation • Self-call of core component is not redirected through wrappers • Some wrapper composition logic should not be under control of the clients

  35. DatingSystem Agenda Authoriz. Check Wrapper Authoriz. Check Wrapper AccessDenied Exception Handler AccessDenied Exception Handler Group App. Service Group App. Service Calling context must be propagated over entire core system Atomic Agenda Atomic Agenda Coordination Problem

  36. DatingSystem Agenda Authoriz. Check Wrapper Authoriz. Check Wrapper AccessDenied Exception Handler AccessDenied Exception Handler Group App. Service Group App. Service Calling context must be propagated over entire core system Atomic Agenda Atomic Agenda Coordination Problem

  37. Lasagne mechanisms • Underlying run-time component model

More Related