Babel RMI using CORBA

1
Babel RMI using CORBA

• Nanbor Wang and Rooparoni Pundaleeka
  nanbor,roopa_at_txcorp.comTech-X
  CorporationBoulder, CO

CCA Meeting, Jan 25, 2007
Funded by DOE OASCR SBIR Grant DE-FG02-04ER84099
2
DistComp Mixing Distributed Technologies and
Parallelism

• Provide another high-level abstraction for HPC
  infrastructure
• A new dimension for partitioning application
  compositions
• Goal explore the challenges of developing DPHPC
  applications
• Existing CCA implementations are beginning to
  support both models
• Demo on integration done before but not part of
  distributions

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Remoting CCA Components

• Connect distributed parallel computations by
  composing remote-capable proxy components into
  applications
• Hide the distributed aspect from the localized
  parallel CCA framework
• Provide low-cost mechanisms for connecting
  incompatible CCA infrastructures, e.g., Ccafeine,
  Dune, Ccain, and SciRUN

4
Babel RMI Support

• Babel now generates mapping for remote
  invocations
• Allow users to take advantage of different
  remoting technologies through 3rd-party RMI
  Libraries
• We are developing a Babel RMI library
  implementation for CORBA support
• Main developer Rooparoni Pundaleeka
• Summer interns Akshay Dabholkar and Jaiganesh
  Balasubramanian
• And me

5
TaoIIOP Design

• Goal
• Support interoperability with existing CORBA
  objects
• Performance
• Possible approaches
• Encapsulating Babel communication with CORBA Any
  objects
• Mapping Babel communication to CORBA protocols
  directly
• Direct mapping best suits our goal but it
  requires support of certain Babel types
• Still exchange messages in CORBA format
• Allow development of new SIDL-compatible CORBA
  objects
• There exists no direct mapping for SIDL to CORBA
  anyway remoting components can provide
  adaptability for such services
• Based on TAO ORB version 1.5.1 or later
• All special mappings defined under namespace
  taoiiop_rmi

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Special Mappings Complex

• CORBA structs for fcomplex and dcomplex
• struct fcomplex float realfloat imaginary
• Struct dcomplex double realdouble
  imaginary

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Special Mappings Arrays

• CORBA struct for describing layout of
  multi-dimentional arrays
• typedef sequence ltshortgt ArrayDimsenum Types
  A_BOOL, A_CHAR, A_INT, A_LONG, A_OPAQUE,
  A_FLOAT, A_DOUBLE, A_FCOMPLEX, A_DCOMPLEX,
  A_STRING, A_SERIALIZABLEstruct Array_Info
  string key short ordering short
  ndims ArrayDims dims boolean
  reuse_array Types type
• Payloads are flattened into unbounded CORBA
  sequences
• No need to use Array_Info for 1-D arrays
• Need to support user-defined structs in the future

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Server Configurations

• Objects are managed under a Portable Object
  Adapter (POA)
• POAs can be arranged hierarchically
• Each ORB has a RootPOA object
• Our design interoperates with Babels URL parsing
  scheme
• A single child POA handles all Babel
  communications using the default servant policy
• A TaoObject implements the default servant
• Handles local and remote object creation requests
• Manages Babel object instances
• De-multiplexes incoming Babel invocations to
  proper instances
• Other CORBA servants can still co-exist on other
  POAs

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Client-side Operation Invocations

• Common Data Representation (CDR) a binary
  serialization format
• An Operation_Details object encapsulates all
  information related to invocations in TAO
  outgoing CDR and incoming CDR strings
• TaoIIOPvocation class support both Invocation and
  Response interfaces to share the operation
  details object
• Need to extend Operation_Details to expose
  internal CDR data members
• Need to de-optimize TAO argument handling
• No longer requies full argument lists

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Server-side Request Handling

• CDR handling is similar to the client-side
• Need to extend TAOs ServerRequest class to
  expose internal data members
• A default servant handles all babel invocations
• The default servant is always installed under a
  specific chile POA
• Requests are demultiplexed to babel objects based
  on the instance ID
• Perhaps we want to manage Babel objects in a
  hierarchical manner to enhance performance?
• Currently does not support system assigned
  instance IDs (requires explicit registration to
  the ORB)

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Client-side initialization

• Need to register TaoIIOP Protocol Factory
• sidlrmiProtocolFactory (taoiiophandle,
  taoiiop.rmi.TaoIIOPHandle)
• Create/connect to remote objects
• URL in the form of taoiiop//serverport/objid
• TaoIIOP convert it to CORBA URLs automatically

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Current Status

• Support
• Both client and server side
• Interoperability with regular CORBA server
• Most primitive types, complexes, strings, and
  arrays of them
• Things to do
• Exception support
• Opaque and serializable support
• Non-blocking and oneway supports CORBA supports
  it
• Remotable object incarnation strategies
• Regression tests?
• We will package TaoIIOP and make it available on
  the web soon
• Email (nanbor_at_txcorp.com) if you would like to
  try it out

13
Future Works in Distcomp

• Planned tasks
• Benchmarking r-array and SIDL array access time
• Support user-defined data struct for FORTRAN 2003
• Distributed-component generator tools
• Examine and review different composition
  strategies for DPHPC applications
• Develop example DPHPC applications