CORBA/RMI issues in Nile

Authors:

F. Handfield (University of Texas, Austin, TX USA)

D. Mimnagh (University of Texas, Austin, TX USA)

M. Ogg (University of Texas, Austin, TX USA)

L. Zhou (University of Florida, Gainesville, FL USA)

Presented by:

D. Mimnagh (University of Texas, Austin, TX USA)

CHEP 2000

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Overview

• What is Nile?

• Distributed Object Architecture– CORBA– RMI

• Future work

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What is Nile?

• Nile: Distributed computing solution for CLEO

– fault-tolerant (recover from resource failure)– self-managing (sophisticated resource scheduling) – heterogeneous (will run anything anywhere)

• Designed for HEP– track reconstruction– data analysis– simulation

• But very generic

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Nile Architecture

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History of Nile• Initially

– C++– Electra, for the CORBA ORB – Isis for replication

• Isis product was eventually abandon by its vendor

• C++ was hard to use portably

• Nile rewritten in Java with CORBA

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Distributed Object Architecture• Computation is distributed

• Should we distribute the control system?– scalability– resilience– separation of function– additional failure modes– error handling

• Choices available:– CORBA, RMI, DCOM

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Nile with CORBA• Code specified by IDL to Java bindings

– write interfaces in IDL– compile IDL to Java for interfaces, proxies

helper classes etc...– implement Java interfaces

• Successful robust Nile implementation achieved– HERA-B MC– CLEO II MC

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• Restrictive object model– pass data only– not Serializable– members are public – classes are final

• Under specified– OMG politics?

• Name Service is single point of failure• ORB supplier

– bug reporting

• Scaling problems

CORBA Issues

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Nile with RMI• No code mappings needed

– write interfaces in Java– implement Java interfaces – compile implementation to proxies classes

• Improved Nile prototype (see E301)– no deadlocks– no scalability problems with 60 CPUs

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RMI Issues• Less complex

– only the essentials functions are provided– fewer lines of code– Java only (could use JNI to get to others)– rudimentary registry service

• Real objects– data + code

• One vendor – better integration– no alternatives

• It does the job!

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Future Work• Complete port to RMI

– robust fault-tolerance,GUIs, etc...

• CLEO III data processing and analysis– scheduling– data management– comprehensive security

• Enhance Nile with RMI technologies– Jini

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Jini• Lookup Service

– Name Service– transparent replication– object database

• Lease mechanism

• Distributed events