Structured Composition of Dataflow and Control-Flow for Reusable and Robust Scientific Workflows
Data-centric scientific workflows are often modeled as dataflow process networks. The simplicity of the dataflow framework facilitates workflow design, analysis, and optimization. However, some workflow tasks are particularly ''control-flow intensive'', e.g., procedures to make workflows more fault-tolerant and adaptive in an unreliable, distributed computing environment. Modeling complex control-flow directly within a dataflow framework often leads to overly complicated workflows that are hard to comprehend, reuse, schedule, and maintain. In this paper, we develop a framework that allows a structured embedding of control-flow intensive subtasks within dataflow process networks. In this way, we can seamlessly handle complex control-flows without sacrificing the benefits of dataflow. We build upon a flexible actor-oriented modeling and design approach and extend it with (actor) frames and (workflow) templates. A frame is a placeholder for an (existing or planned) collection of components with similar function and signature. A template partially specifies the behavior of a subworkflow by leaving ''holes'' (i.e., frames) in the subworkflow definition. Taken together, these abstraction mechanisms facilitate the separation and structured re-combination of control-flow and dataflow in scientific workflow applications. We illustrate our approach with a real-world scientific workflow from the astrophysics domain. This data-intensive workflow requires remote execution and file transfer in a semi-reliable environment. For such work-flows, we propose a 3-layered architecture: The top-level, typically a dataflow process network, includes Generic Data Transfer (GDT) frames and Generic remote eXecution (GX) frames. At the second level, the user can specialize the behavior of these generic components by embedding a suitable template (here: transducer templates for control-flow intensive tasks). At the third level, frames inside the transducer template are specialized by embedding the desired implementation. Our approach yields workflows that are more robust (fault-tolerance strategies can be define by control-flow driven transducer templates) and at the same time more reuseable, since the embedding of frames and templates yields more structured and modular workflows.
- Research Organization:
- Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 883516
- Report Number(s):
- UCRL-CONF-215235; TRN: US200615%%86
- Resource Relation:
- Conference: Presented at: Symposium on Applied Computing, Dijon , France, Apr 23 - Apr 27, 2006
- Country of Publication:
- United States
- Language:
- English
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