1. A Novel Approach to Workflow Management in Grid Environments Frank Berretz*, Sascha Skorupa*, Volker Sander*, Adam Belloum** 15/04/2010 * FH Aachen - University of Applied Science, GER ** University of Amsterdam, NL

2. © FH AACHEN UNIVERSITY OF APPLIED SCIENCES15. April 2010 | 2 Taxonomy of Grid Workflow Systems >Common Architecture Push-based Job Distribution >Requirements >UNICORE Workflow System >Consequences Pull-based Approach >Benefits & Challenges >General Architecture Prototype Implementation >UNICORE Grid Middleware >jBPM Workflow Engine Outline

3. © FH AACHEN UNIVERSITY OF APPLIED SCIENCES15. April 2010 | 3 Taxonomy of Grid Workflow Systems Common Architecture Workflow Design & Definition Grid Users Build Time Run Time Workflow Execution & Control Interaction with Grid resources Grid Workflow Application Modeling & Definiton Tools Workflow Scheduling Data MovementFault Movement Grid Workflow Enactment Service Grid Middleware Grid Resources Grid Information Services Resource Info Service Application Info Service interaction with inforamtion services workflow change Grid Workflow Specification Source: Jia Yu and Rajkumar Buyya

4. © FH AACHEN UNIVERSITY OF APPLIED SCIENCES15. April 2010 | 4 Push-based job distribution requires >Efficient resource discovery and selection processes >Detailed knowledge of available resources >Well-defined interfaces of resources >Up-to-date and confidential information systems >Adapt VO schedulers and local schedulers >Proper Access Control Lists from resource providers Push-based Job Distribution Requirements

5. © FH AACHEN UNIVERSITY OF APPLIED SCIENCES15. April 2010 | 5 Push-based Job Distribution UNICORE Workflow System 1.Splitting workflow into sequence of WAs and send them to a orchestrator. 2.Filter appropriate resources by requesting an information service. 3.Information Service requests all available Grid sites. 4.Evaluate requests from multiple VOs. 5.Response concrete resource endpoint. 6.Service Orch. forwards JSDL to known interface. 7.Site performs authorization by mapping CA to a local account. 8.XNJS sends job through the TSI to a physical computing resource. 9. – 11. Callback chain Workflow Engine Service Orchestrator Target System Interface UNICORE Atomic Services OGSA Interface XNJS Workflow Management System Computing Resource WA JSDL Information Service (CIS / GLUE 2.0) XUUDB 1 2 3 4 5 6 7 89 10 11

6. © FH AACHEN UNIVERSITY OF APPLIED SCIENCES15. April 2010 | 6 Scalability: Information systems and schedulers may become bottlenecks with respect to the amount of… >Users and resources >Parallel branches inside a workflow (parameter studies) Cross Grid Scheduling: >Side effects caused by resources in multiple Grids >Limitation of resource candidates to resources of a particular Grid (Open community approach?) Heterogeneity: Grid Workflow Systems typically deal with computational resources >Cumbersome integration of special resources like human interaction (lack of integrating emerging standards) >Complex decision processes by humans might influence further workflow steps (e.g. qualitative assessment criteria) Push-based Job Distribution Consequences

7. © FH AACHEN UNIVERSITY OF APPLIED SCIENCES15. April 2010 | 7 Alternative Idea Pull-based Job Distribution Strategy Workflow system sends task to an intermediary repository Resources act autonomously and adapt to the repository Any kind of resource can actively request the repository Resources apply for defined roles to receive tasks according to their capabilities Resources have to authenticate against the task repository

8. © FH AACHEN UNIVERSITY OF APPLIED SCIENCES15. April 2010 | 8 Architectural Concept for the Pull Model

9. © FH AACHEN UNIVERSITY OF APPLIED SCIENCES15. April 2010 | 9 Benefits >Scheduler and brokering components are now optional >Simplified integration of special resources like humans, telescopes or medical devices >Reduced administrative VO management overhead at resource sites >Support actors across organizational boundaries (community approaches) Challenges >Bottleneck problem should not be shifted to the task repository >Submitted jobs run the risk of starvation (SLAs!) >Appropriate security and provenance frameworks needed Benefits & Challenges of Pull-based Approach

10. © FH AACHEN UNIVERSITY OF APPLIED SCIENCES15. April 2010 | 10 Integrate Pull Approach to an existing Grid Middleware Extending UNICORE Grid middleware Use existing XML Tuple Space as repository Integrate jBPM Workflow Engine as client for the space 1.User starts workflow 2.Engine writes job to space 3.Resource takes job from space 4.Resource executes job locally 5.Resource finishes job 6.Engine receives notification by the space and resumes workflow Grid User(s) UNICORE Rich Client jBPM Engine Workflow Management System WA 1 1 Resource Provider(s) Job Taker XML Space(s) 2 35 6 4 UNICORE Hosting Env.

11. © FH AACHEN UNIVERSITY OF APPLIED SCIENCES15. April 2010 | 11 Conclusions: >Pull-based job distribution strategies are currently missing in Grid systems >But it could be used as an alternative model for certain application scenarios (heterogeneous resources, high-throughput computing, …) Summary and Outlook

12. © FH AACHEN UNIVERSITY OF APPLIED SCIENCES15. April 2010 | 12 Further steps: >XML space should be replaced by a scalable task repository >Among the simple Job-Takers more complex client systems should be implemented to integrate special resources (humans) into Grids >Hybrid push/pull distribution strategies as an option >Performance and scalability analysis This work should result in a refined architecture to address the challenges of pull-based approaches Summary and Outlook

13. FH Aachen University of Applied Science Campus Jülich Ginsterweg 1 52428 Jülich T +49. 241. 6009 53277 berretz@fh-aachen.de, skorupa@fh-aachen.de www.fh-aachen.de © FH AACHEN UNIVERSITY OF APPLIED SCIENCES | FRANK BERRETZ, SASCHA SKORUPA | GINSTERWEG 1 | 52428 JÜLICH | WWW.FH-AACHEN.DE