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Dynamic and generic workflows in .NET

Dynamic and generic workflows in .NET. Bart De Smet. Agenda. Introduction Workflow: what and why? Research Dynamic workflows Methodologies Instrumentation framework Generic composition Generic data-driven workflows Design decisions Performance and conclusion. Introduction.

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Dynamic and generic workflows in .NET

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  1. Dynamic and generic workflows in .NET Bart De Smet Vakgroep Informatietechnologie – Breedbandcommunicatienetwerken (IBCN)

  2. Agenda • Introduction • Workflow: what and why? • Research • Dynamic workflows • Methodologies • Instrumentation framework • Generic composition • Generic data-driven workflows • Design decisions • Performance and conclusion Vakgroep Informatietechnologie – Breedbandcommunicatienetwerken (IBCN)

  3. Introduction • What is workflow? • Graphical construction of applications • Business processes, human workflows • State machines versus sequential workflows • Typically long-running processes • E.g. order processing with human approval • Key advantages • Graphical inspection by various stakeholders • Availability of runtime services • Raise the level of abstraction • E.g. persistentie, tracking, scheduling, etc Vakgroep Informatietechnologie – Breedbandcommunicatienetwerken (IBCN)

  4. Introduction • Windows Workflow Foundation • Workflow in a general purpose framework • Part of Microsoft’s .NET Framework 3.0 Vakgroep Informatietechnologie – Breedbandcommunicatienetwerken (IBCN)

  5. Introduction Sequential workflow definition If-Else Parallelism Activity Interactions Vakgroep Informatietechnologie – Breedbandcommunicatienetwerken (IBCN)

  6. Research • Dynamic workflows • Problem statement • Long-running versus changing business environment • Visual obstruction by aspects • Adaptation at run-time • Modification of workflow instances • Injection of aspects, e.g. logging, authorization, etc • Generic composition • Problem statement • Repetitive tasks, e.g. data querying and retrieval • Ultimate vision: composition by the end-users • Generic blocks for composition Vakgroep Informatietechnologie – Breedbandcommunicatienetwerken (IBCN)

  7. Agenda • Introduction • Workflow: what and why? • Research • Dynamic workflows • Methodologies • Instrumentation framework • Generic composition • Generic data-driven workflows • Design decisions • Performance and conclusion Vakgroep Informatietechnologie – Breedbandcommunicatienetwerken (IBCN)

  8. Dynamic workflows • What? • Dynamic adaptation of workflow instances • Examples • Changing business policy (e.g. extra order approval) • Injection of runtime aspects (e.g. logging, auth’z) • Inspection of workflow instances (e.g. debugging) • How? • WF Dynamic Updates • Flexible framework-level mechanism • Additional custom tools layered on top • Instrumentation framework Vakgroep Informatietechnologie – Breedbandcommunicatienetwerken (IBCN)

  9. WF Dynamic Updates • Internal modification • By code inside a running workflow instance • Access to internal state • Fast • Prior knowledge of adaptation kinds required • Requires pre-configured communications to the outside • External modification • By code at the host level • Access to external state • Adaptation in an ad-hoc manner • Relatively slow • Timing issues concerning the state an instance is in Vakgroep Informatietechnologie – Breedbandcommunicatienetwerken (IBCN)

  10. Instrumentation • Best of both worlds • External modification + internal modification • Suspension points for exact timing Instrument RuntimeEvent Handlers Inspect, inject,resume Vakgroep Informatietechnologie – Breedbandcommunicatienetwerken (IBCN)

  11. Instrumentation • Examples • Logging • Debugging • Time measurement • Authorization • Tracking • Real-time inspection • Execution history • Workflow Monitor Vakgroep Informatietechnologie – Breedbandcommunicatienetwerken (IBCN)

  12. Agenda • Introduction • Workflow: what and why? • Research • Dynamic workflows • Methodologies • Instrumentation framework • Generic composition • Generic data-driven workflows • Design decisions • Performance and conclusion Vakgroep Informatietechnologie – Breedbandcommunicatienetwerken (IBCN)

  13. Flowcharts Iterative Error handling Decision logic Calculations Reporting Vakgroep Informatietechnologie – Breedbandcommunicatienetwerken (IBCN)

  14. Generic composition • What? • Generic building blocks • Reusable blocks for workflow composition • Typical tasks such as data retrieval • Important design decisions • Easy translation from flowchart to workflow • Dataflow versus workflow • Combination with Service Oriented Architectures • Workflow versus procedural: what’s the cost? • How? • Custom activities in WF • Designer rehosting Vakgroep Informatietechnologie – Breedbandcommunicatienetwerken (IBCN)

  15. Generic blocks • Data retrieval • Data gathering block • IQueryManager • DBMS independent • PropertyBag storage • Iteration • Foreach block • Decision logic • IfElse + conditions • Reporting of results Vakgroep Informatietechnologie – Breedbandcommunicatienetwerken (IBCN)

  16. Design decisions • To iterate or not to iterate... • Stale data during iteration • Loop body long-running? • Persistence is your enemy • Granularity of workflow instances • Chatty or chunky? • Reduction of database communication • More logic at the database tier? • Introduces workflow need at a different layer • “Dataflow” isn’t trivial • Bindings required for explicit dataflow (no pipelining) • Generic & weakly typed versus specific & strongly typed Vakgroep Informatietechnologie – Breedbandcommunicatienetwerken (IBCN)

  17. Service oriented architecture • Workflow level • Granularity and invocation mechanism? • Block level • Publish block functionality (e.g. query manager) • Windows Communications Foundation (WCF) • Keep internal communication efficient • Make external communication WS-* compliant Vakgroep Informatietechnologie – Breedbandcommunicatienetwerken (IBCN)

  18. Result Vakgroep Informatietechnologie – Breedbandcommunicatienetwerken (IBCN)

  19. Rehosting Vakgroep Informatietechnologie – Breedbandcommunicatienetwerken (IBCN)

  20. Agenda • Introduction • Workflow: what and why? • Research • Dynamic workflows • Methodologies • Instrumentation framework • Generic composition • Generic data-driven workflows • Design decisions • Performance and conclusion Vakgroep Informatietechnologie – Breedbandcommunicatienetwerken (IBCN)

  21. Procedural versus workflow Iterative workflows • Procedural is better • WF scheduler overhead Data gathering • Parallelism reduces damage Let the runtime servicesdo useful work! Vakgroep Informatietechnologie – Breedbandcommunicatienetwerken (IBCN)

  22. Exploiting parallelism Intra-workflow Inter-workflow Boost scheduler Vakgroep Informatietechnologie – Breedbandcommunicatienetwerken (IBCN)

  23. Instrumentation • Internal modification • External modification Impact by scheduler • Instrumentation framework • Reduces # of ad-hoc external modifications • Workflow is set to idle by suspension points Vakgroep Informatietechnologie – Breedbandcommunicatienetwerken (IBCN)

  24. Conclusion Vakgroep Informatietechnologie – Breedbandcommunicatienetwerken (IBCN)

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