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Orchestration of an OGSI-enabled scientific application using the Business Process Execution Language Ben Butchart Wolfgang Emmerich University College London [email protected] [email protected] Grids and Applied Language Theory (GAL2003)

Ben Butchart Wolfgang Emmerich University College London [email protected]

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Orchestration of an OGSI-enabled scientific      application using the Business Process Execution Language. Grids and Applied Language Theory (GAL2003). Ben Butchart Wolfgang Emmerich University College London [email protected] [email protected]. Overview. - PowerPoint PPT Presentation

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Page 1: Ben Butchart  Wolfgang Emmerich University College London b.butchart@cs.ucl.ac.uk

Orchestration of an OGSI-enabled scientific     application using the Business Process Execution Language

Ben Butchart

Wolfgang Emmerich

University College London

[email protected]

[email protected]

Grids and Applied Language Theory (GAL2003)

Page 2: Ben Butchart  Wolfgang Emmerich University College London b.butchart@cs.ucl.ac.uk

Overview

• How we became interested in workflow• Why we chose BPEL• A BPEL appetizer• Shortcomings of existing BPEL implementations• Shortcomings of BPEL language itself• Overcoming some problems• Comparison with GSFL• Conclusion and future work• Discussion

Page 3: Ben Butchart  Wolfgang Emmerich University College London b.butchart@cs.ucl.ac.uk

The Beginning…

A messy but beautiful data flow diagram

Page 4: Ben Butchart  Wolfgang Emmerich University College London b.butchart@cs.ucl.ac.uk

Control logic of the Polymorph prediction application (not distributed)

configure system

loop 1..29 space groups

loop 1..X high denisty structurescollate results

molpak

dmarel

yes

is last structure ?

no

yes

no

is last spacegroup ?

Page 5: Ben Butchart  Wolfgang Emmerich University College London b.butchart@cs.ucl.ac.uk

Control logic of the distributed polymorph prediction application

molpak molpak molpak

dmarel dmarel dmarel dmarel dmarel dmarel

collate results

configure system

Page 6: Ben Butchart  Wolfgang Emmerich University College London b.butchart@cs.ucl.ac.uk

So why BPEL ?

• WSFL and XLANG deprecated• Microsoft, IBM, BEA triumvirate powerful

market force• Submitted to OASIS for standardization• First implementations already available for

evaluation (IBM BPWS4J, Collaxa)• Do not want to diverge from standard Web

Services technology set

Page 7: Ben Butchart  Wolfgang Emmerich University College London b.butchart@cs.ucl.ac.uk

Instantiating SOAP message

<soapenv:Body> <runPoly xmlns="http://poly"> <ns1:atomArray xmlns:ns1="http://www…/cml2/core"> <ns1:atom elementType="H" x="3.17" y="2.43“ z="0.02"/> <ns1:atom elementType="H" x="-1.74" y="2.61" z="-0.38"/> </ns1:atomArray> <spacegroups> <spacegroupLabel>AA</spacegroupLabel> <spacegroupLabel>AB</spacegroupLabel> </spacegroups> <ns2:crystal z="1" xmlns:ns2="http://www…/cml2/core"> <ns2:scalar title="alpha" units="deg">0</ns2:scalar> <ns2:symmetry id="" spaceGroup=""/> </ns2:crystal> </runPoly> </soapenv:Body>

Page 8: Ben Butchart  Wolfgang Emmerich University College London b.butchart@cs.ucl.ac.uk

BPEL Example

<sequence name="sequence"> <receive name="receive" partner=“user" portType="p:PolyPort" operation="runPoly" container="request“ createInstance="yes"/> <assign> <copy> <from container="request" part="atomArray"/> <to container="molpakrequest" part="atomArray"/> </copy> </assign>

<assign> <copy> <from container="request" part="crystal"/> <to container="molpakrequest" part="crystal"/> </copy> </assign>

Page 9: Ben Butchart  Wolfgang Emmerich University College London b.butchart@cs.ucl.ac.uk

BPEL Example

<assign> <copy> <from container="request" part="spacegroups“

query="./spacegroupLabel[position()=1]" /> <to container="molpakrequest" part="crystal"

query="./ns2:symmetry/@id" /> </copy></assign>

<invoke name="invoke1" partner="provider" portType="mpak:MolpakPort"

operation="runMolpak" inputContainer="molpakrequest"

outputContainer="molpakresponse"/>…

</sequence>

Page 10: Ben Butchart  Wolfgang Emmerich University College London b.butchart@cs.ucl.ac.uk

BPEL Features

• Loop and control logic• XPath query assignment• Recursive Composition• Synchronous and asynchronous

communication• Concurrent execution• Correlated messages• Event handling• Fault handling

Page 11: Ben Butchart  Wolfgang Emmerich University College London b.butchart@cs.ucl.ac.uk

Shortcomings of BPEL implementations

• Binding to a URL expected at deployment time

• Early implementations could not cope with OGSI extensions to WSDL

• Or properly handle imports• Dynamic creation of new process instances to

improve scalability• Steering – change process during execution

Page 12: Ben Butchart  Wolfgang Emmerich University College London b.butchart@cs.ucl.ac.uk

Shortcomings of BPEL language

• Need placeholder objects to support some assignments

• Data aggregation - No way to temporarily collate results

• Cannot specify mechanism for binding (WSDL, UDDI, OGSAFactory)

• Limited lifecycle interface (just receive, pick terminate)

• Verbose• Does not support peer communication

Page 13: Ben Butchart  Wolfgang Emmerich University College London b.butchart@cs.ucl.ac.uk

The scalability problem

After Krishnam, Wagstrom, LaszewskiGSFL: A Workflow Framework for Grid Services

Workflow Engine Workflow Engine

Compute Service

Compute Service

Compute Service

Compute Service

Compute Service

Compute Service

Page 14: Ben Butchart  Wolfgang Emmerich University College London b.butchart@cs.ucl.ac.uk

<invoke name="invoke1" partner="provider" portType="mpak:MolpakPort" operation="runMolpak" inputContainer="molpakrequest" outputContainer="molpakresponse"/>

getBindingURL(PortType)

BPEL Parser

AbstractBinding

WSDLBinding

UDDIBinding

OGSA Registry

OGSA FactoryBinding

OGSA Registry

UDDI Registry

Molpak serviceCreate instance

<service name="MolpakService"><port><soap:address location= "http://tapas.cs.ucl.ac.uk: 8080/ogsa/services/"/></port></service>

Late binding

Page 15: Ben Butchart  Wolfgang Emmerich University College London b.butchart@cs.ucl.ac.uk

Scalability

Workflow Engine

Compute Service

Compute Service

Compute Service

Workflow Engine

Compute Service

Compute Service &Workflow Engine

Compute Service

compute1

compute2

compute3

Page 16: Ben Butchart  Wolfgang Emmerich University College London b.butchart@cs.ucl.ac.uk

How we solve the problems

• late binding: extra URL binding mechanisms• scalability: recursive composition• scalability: group binaries into single WS port type • scalability: dynamic deployment and delegation• steering: use BPEL event handling functionality• aggregation: use a dedicated web service• verbose: use GUI/XSLT

Page 17: Ben Butchart  Wolfgang Emmerich University College London b.butchart@cs.ucl.ac.uk

Other Web Service Workflow Languages

• WSFL and XLANG – now superseded by BPEL

• GSFL – extension to WSFL to support Grid requirements

• SWFL – another extension to WSFL • Scufl (taverna) / Freefluo

Page 18: Ben Butchart  Wolfgang Emmerich University College London b.butchart@cs.ucl.ac.uk

Comparison with GSFL

• recursive composition

• correlated messages

• separates data flow

• peer data flow modelling

• binding mechanism configurable

• WS standard

• cross vendor support

• fault handling and compensation

• concurrent control flow

• message part assignment

• Xpath assignment

• implementations available

• recursive composition

• correlated messages

• separates data flow

• peer data flow modelling

• binding mechanism configurable

• WS standard

• cross vendor support

• fault handling and compensation

• concurrent control flow

• message part assignment

• Xpath assignment

• implementations available

GSFL BPEL

Page 19: Ben Butchart  Wolfgang Emmerich University College London b.butchart@cs.ucl.ac.uk

Conclusion

• Can use BPEL for modelling grid applications – no real need for extensions

• But we need an implementation that is Grid enabled

• Might not need full implementation • We should stick with WS technology set if at

all possible

Page 20: Ben Butchart  Wolfgang Emmerich University College London b.butchart@cs.ucl.ac.uk

Integration with Scheduler (Sun Grid Engine)

2.getBindingURL(PortType)Trader

Binding

SGE

3. Run a proxy job (jobID, traderURL)

molpak serviceisntance

OGSARegistry

Trader

SGE Wrapper

4. Run a proxy job (jobID, traderURL)

Dummy Process(blocks)

5. runDummy.sh(jobID,traderURL)

BPEL Engine

1.getBindingURL(PortType)

9.invocation completed

6. SGEchooseMe(jobID,myURL)

10.kill

7. search for instance

8.invoke service

compute node

Page 21: Ben Butchart  Wolfgang Emmerich University College London b.butchart@cs.ucl.ac.uk

Late binding: deployment descriptor

<service name="poly/PolyProviderFactoryService/poly1"> <requestFlow> <handler type="BPELRequestHandler"/> </requestFlow> <responseFlow> <handler type="BPELResponseHandler"/> </responseFlow> <parameter name="name" value="Polymorph process workflow"/> <parameter name="className" value="poly.PolyProvider“ <parameter name=“bindingMechanism" value=“Registry"/></service>