An Interactive Browser For BaBar Databases

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An Interactive Browser ForBaBar Databases

• Adeyemi Adesanya
• Stanford Linear Accelerator Center

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Why?

• We need an interactive Objectivity/DB utilities,
  for physicists and administrators
• Program supplied by vendor offers limited
  functionality and does not scale

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BaBars Functional Demands

• Scalability! 64k database files
• Presenting the right abstraction
• No general external product is BaBar-aware
• A logical, BaBar database hierarchy needs to be
  incorporated

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Java

• Suitability
• Comprehensive set of GUI components
• Platform independent for wide deployment
• Objectivity/Java binding has limitations related
  to language interoperability (today).

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CORBA

• A STANDARD for distributed inter-object
  communication (http//www.omg.org)
• ORBs form the middleware layer along with the
  IIOP
• Java/C ORB bindings readily available

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The framework

• 100 Java provides the client GUI
• C servers handle Objectivity access
• 1 server process per Objectivity federation
• NamingService stores server addresses

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Key features

• View the Database Event collection hierarchy
• Iterate through collections using simple
  selection (tags)
• Access individual events and browse their headers
• Identify cloned components
• Scan a collection for databases

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CORBA performance

• A high-level protocol, not an alternative to
  TCP-IP!
• Data marshalling is a major factor
• Consider size/complexity of data types
• Database IO overshadows CORBA latency

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Minimizing the overhead

• Server Models the GUI components
• No persistent objects are converted to CORBA
• Transactions are kept as short as possible
• Warn user of locking issues if necessary

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The TAO ORB

• Designed for real-time environments
• Aim is reliable, predictable CORBA service
• Optimized client server stubs
• Fine grained thread control

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Multithreading

• Reduce idle CPU time during IO tasks
• Exploit multiprocessor hardware
• Priority control
• two models currently in use
• thread-per-connection
• thread pool

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Future admin. tools

• Browser database tasks strictly read-only
• Develop separate GUI for administrators
• Aid import/export of files between sites
• Search engine
• Drag and drop files and event collections

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Summary

• CORBA offers
• distributed object communication
• platform interoperability
• more than just a transport protocol
• 100 Java for platform independent GUIs
• Not all ORBs are created equally