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OGSA Lessons:
A Practical View
Getting OGSA Going 2
June 12, 2002
Dr. David Snelling - Fujitsu Laboratories of Europe
Fujitsu © 2002
Overview
Application Perspective
RealityGrid Application Steering
Implementation Architecture
(Web Services ∪ Unicore) = OGSA
Open Grid Services Architecture
Port Types, Service Types, Service Data, ...
Lessons
Based on implementation experience.
Future Directions
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Application Perspective
Supercomputer Site
Start
Sample
Steer
WS Client
Transfer Final Results
Data Archive Site
Results
Archive
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Application Black Box
Application Resource
Including (arbitrarily complex) runtime.
Configured and advertised by the site.
Basic Application
Input File
Output File
Control
Steerable Application
Sample
Basic Application +
Sample File created periodically
Control File re-read periodically
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Input
Black
Box
Output
Implementation Architecture
Web Services Client
Web Services
Authentication
http(s) + SOAP
Web Services Server (GLUE)
Unicore Servlet
Unicore
Authentication
Unicore Protocols
Unicore
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Client Side
OGSA Implementation
serviceTypes
Basic portTypes
GridService
Registry
HandleMap
Factory
Notification
Factory
RegistryAndMapper
Grid Service portTypes
JobGridService
SteeringGridService
NotificationService
JobGridService
SteeringGridService
NotificationService
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Easy OGSA Lessons
PrimaryKey portType is redundant.
Was thought to expose a useful hosting environment handle.
GSH + GSR model makes sense.
Separates finding from binding.
Compatibility assertions are a problem.
Say little more than “This one is like that one.”
Who says so?
Objects by the back door, please use the front door.
I like the idea of a Compatability portType.
GLUE + Unicore is an effective hosting platform.
2 person-months effort 3 months elapsed.
OGSA needs a lot more work.
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Interesting Lessons
Web Services alone can go a long way.
OGSA Architecture captured at Java level.
Web Services view is a flat projection.
Tooling and introspection are important for uptake.
Pull framework desirable for notification.
Clients live behind firewalls.
For GS to GS it is not as critical.
Unicore has a pull model only.
Object hierarchy of Grid Services makes sense.
A natural Super Type in GridService
Extension of JobGridService to SteeringGridService.
Aggregation of Resgistry and HandleMap”
However, proceed with caution.
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More Interesting Lessons
Object Issues
Interface inheritance and extension is a good thing.
No overloading?
Replaces ServiceImplementation and part of
CompatabilityAssertions
Multiple classes of ServiceData exist.
Static: Interface related, implementation independent.
Binding: Platform specific binding data.
Instantiation: In Unicore, site specific resources
Dynamic: Job state changes.
Performance aware bindings are needed.
HTTP/SOAP limited in performance and structure size.
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Very Interesting Lessons
Security provided at binding only is inadequate.
Unicore in ASP mode works fine.
Framework extensions needed for full Unicore.
Not clear if Unicore trust model is possible.
Next specification needed.
RPC vs Document “Look and Feel”
Most portTypes are RPC like - better portability.
Unicore is Document like, with a standardized document.
Some have structured arguments that determine function.
Globus implicit semantics appear here and there.
Good balance comparatively:
MPI: Too RPC like; qsub: Too Document like
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Future Directions
Let People Play, and then Listen
Visit www.unicore.org and follow Download and Server.
For Unicore side, try www.fz-juelich.de/unicore-test
Find a GridServices Platform
Support for serviceType and static ServiceData
Study the Security Issue
Extend/Re-architect the Demonstrator
Better internal API’s.
Include more flexible security framework.
Convert the AbstractJobObject to WSDL.
This would be interesting to compare to WSFL.
Pallas could develop an OGSA Client.
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Demonstration
Initial State
Gss = 2.0
Gss = 2.0
Gss = 0.5
Gss = 0.5
Gss = 1.8
Gss = 1.8
Gss = 1.8
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