10 Sep 2005

NVO Summer School 2005 1

Managing VO data and process flows

Matthew J. GrahamCACR/Caltech

THE US NATIONAL VIRTUAL OBSERVATORY

10 Sep 2005

NVO Summer School 2005 2

Overview

• Astronomical data• VOStore/VOSpace• Workflows• Astrogrid workflow• CEA

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The importance of data

• Data is the raison d’être of the VO• LSST is the data source nonpareil

– data rates of 540MB/s ~16TB in 8 hrs– final archive > 3PB of data

VO Wheel™

• Well-established ways of handling distributed data:

– SRB– PVFS– OGSA-DAI

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Data use cases

• Client has data:– stored locally: transfers it to service– stored locally: service retrieves it– stored elsewhere: service retrieves it

• Service generates data:– stores it locally: notifies client of location– transfers it to the client’s local store– transfers it to a client-designated store

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VOStore

• Provides a uniform interface to existing or new data storage locations (Facade pattern)

• Structured/unstructured data both first level• Methods:

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• get• put• list / listAll• importInit• importData (sync/async)• exportInit• exportData (sync/async)

• delete• rename

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VOSpace

• Orchestrates VOStores:

– data collections: directories, user-defined– authorisation: user groups – processing efficiency: where is the nearest copy?

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• move• copy• identifiers

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A virtual super-peer data network?

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How to manage the flows?

• Way of describing a flow:– processes/steps, inputs/outputs, serial/parallel

execution, control logic, variables, inline scripting– preferably XML (verbose but rigourous)

• Way of controlling a flow: engine• e-Science vs. e-Business:

– open-ended vs. closed– verification and publication– static vs. dynamic workflows– volume and type of data– meta-transactions– customer, manager and user vs. scientist

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Workflow patterns

Sequence:

Parallel split Synchronisation

AND

XOR Exclusive choice

Simple Merge

Multi choice

Multi Multi Merge

Multi + Synchronizing Merge

Multi + Multi

Multi + Discriminator

Deferred choice

Multiple Instances with/out Synch

Implicit termination

Interleaved Parallel Routing

Milestone

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Workflow kerfuffle

• Workflow languages: BPEL (BPEL4WS, WSBPEL, WSFL, XLANG), BPML, WS-CDL (WSCL, WSCI) , XPDL, BPSS, PSL, AGWL, DGL, DPML, GJobDL, GSFL, GFDL, GWorkflowDL, MoML, SWFL, YAWL, SCUFL/Xscufl, WPDL, PIF, PSL, OWL-S, xWFL, XPL, INCA

• Workflow engines: Taverna, Kepler, Pegasus, DiscoveryNet, Triana, SPA, Geodise, ICENI, Askalon, GridNexus, BioPipe, BizTalk, BPWS4J, DAGMan, GridAnt, GJH, GRMS, GWFE, GWES, ITIEE, JIGSA, Karajan, ScyFLOW, SDSC Matrix, SHOP2, wftk, YAWL Engine, WFEE

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Astrogrid workflow components

• JES (Job Execution System)– Astrogrid workflow engine– Manages control flow– Runs steps in a controlled asynchronous fashion

• CEC (Common Execution Controller)– Manages step execution– Manages data flow

• CEA (Common Execution Architecture) apps– datacenters: support complex quesries against

archives– processing: consume data files and reduce them

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Astrogrid workflow schematic

Portal

Registry

MySpace

Command LineCEA

Datacenter CEA

JES

Clientlibrary

CEC

Save/load workflow Save/load data

Resolve application

Application list

Submit workflow

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Astrogrid workflow language

<workflow name=“a workflow”><description>description of the workflow</description>

<sequence/flow><set var=“dec” value=“15”/><step name=“a” result-var=“a-results”>

<tool name=“toolA” interface=“simpleInterface”><input>

<parameter name=“RA”><value>21</value></parameter>

<parameter name=“Dec”><value>${dec}</value></parameter>

</input><output>

<parameter name=“results ”indirect=“true”> <value>ftp://aServer/myResults</value></parameter>

</output></tool>

</step><step name=“b”>…

</sequence/flow><script>…<if test=…> <while test=…> <for var=… items=…> <parfor var=… items=…> <try>

<catch></workflow>

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CEA

• Create a uniform interface and model for an application and its parameters

• Provides higher level description than WSDL:– Restrict how interfaces can be expressed– Provide specific semantics for astronomical quantitites– Extra information, such as default values, GUI labels

• VOResource extensions for a general application• Provide asynchronous operation:

– callback, polling and job identification

• Allow separate data and control flows

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Minimum CEA compliance

• Must implement CommonExecutionConnector interface

• Must send a message to services implementing ResultsListener interface

• Should send messages to services implementing JobMonitor interface

• Should perform basic type checking on all parameter types during init phase