TU / e /AIS Group Technische Universiteit Eindhoven University of Technology Modeling Grid Workflows...

TU/e

/AIS GroupTechnische UniversiteitEindhovenUniversity of Technology

Modeling Grid Workflows withColored Petri Nets

Carmen Bratosin, Wil van der Aalst, and Natalia Sidorova

October 22-24, 2007 Aarhus, Denmark

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What is a Grid? A world wide distributed infrastructure

composed by heterogeneous resources linked by common standards.

Status1. Grid technologies available: Globus,

Condor, OGSA-DAI , Taverna etc.2. Workflows for organizing the job flow


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Grid architecture

Resource allocation

User processes

Middleware

Resources layer

User request

s

Resource informati

on

Resource ids

Job descriptions


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Resources

colset Props = list Prop;colset ResID = string;colset Res = product ResID * Props * Props;

- Computing or Storage Elements- Characterized by a set of properties: e.g. CPU etc.


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Grid Workflow

• Two different types of elements:

• Jobs running

• Control elements


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Grid jobs

Requirements: minimal set of properties that a resource should fulfill

Running job: characterized by process instance id and the allocated resource id


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Middleware

fun en((rid,free,busy),req) = m_leq(req,free);fun take((rid,free,busy),req) = (rid,m_min(free,req),m_add(busy,req));fun return((rid,free,busy),req) = (rid,m_add(free,req),m_min(busy,req));


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Patterns: multiple allocation


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Patterns: multiple allocation


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Process mining example

start endprepare log analyze log select algorithm

heuristic miner

check conformance

return results

alpha miner

genetic miner

...+ -

start set parameters

partition log for 10 fold checking

1

+

check results

10

2

...

run algorithm

-

endreturn results


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Verification of grid workflows

Two steps process:1.Structural verification without

resource constraints2.Structural verification with resource

constraints


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Verification of grid workflows: Step 1 (“infinite” resources)

• Wanted property: soundness

• Two additional conditions:

1. the marking of the requirements places remains the same for all the reachable markings and

2. the resource pool place marking in the final state has the same value as in the initial state.

Home Properties-----------------------

Home Markings [28]

Liveness Properties-----------------------

Dead Markings [28] Dead Transition Instances None Live Transition Instances None


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Verification of grid workflows: Step 1

• Wanted property: soundness

• Two additional conditions:

1. the marking of the requirements places remains the same for all the reachable markings and

2. the resource pool place marking in the final state has the same value as in the initial state.

Home Properties-----------------------

Home Markings [28]

Liveness Properties-----------------------

Dead Markings [28] Dead Transition Instances None Live Transition Instances None


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Verification of grid workflows: Step 2 limited amount of resources

• Wanted property: no deadlocks

• Analysis of a grid model with multiple instances and a limited set of resources

Home Properties

-----------------------

Home Markings

None

Liveness Properties

-----------------------

Dead Markings

[420,456,952]


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Correcting process mining workflow

Identified problem: multiple resources are claimed without being released

Solution: Claiming/releasing more resources


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Conclusions• A structural method to design grid workflows

• CPN Tools helped in finding model problems

Future work

• Extend the model with time

• Extend model such that resources can become unreliable

• Analysis of different allocation policies base d on resource history

TU / e /AIS Group Technische Universiteit Eindhoven University of Technology Modeling Grid Workflows...

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