Jargon of the SRB

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Jargon of the SRB

• Java Programming in the Data Grid.
• Lucas Gilbert

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Introduction

• JARGON is a pure java API for interacting with a
  data grid.
• The API provides functionality matching the SRB C
  client API. Including file I/O for local and SRB
  file systems, querying and modifying metadata.

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The Transparent Grid

• The APIs structure, factory methods and
  programming model, unify diverse file systems
  into a single simple interface.
• File handling exactly matches Suns java.io API.
• Factory methods even hide the type of file
  system, e.g. if it is local or remote.
• The API has been developed to allow for the easy
  inclusion of other grid file systems.

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Class Structure

• java.lang.Object      -edu.sdsc.grid.io.Genera
  l            -edu.sdsc.grid.io.Local       
       -edu.sdsc.grid.io.Remote                 
   -edu.sdsc.grid.io.srb.SRB                  -
  ...(other filesystems)

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Connecting to a File System

• Create an account object with your user info
• SRBAccount account
• new SRBAccount( userInfo )
• Then connect to the SRB filesystem.
• SRBFileSystem fileSystem
• new SRBFileSystem( account )

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General, Local, and SRB File

• The filesystem object is used to instantiate new
  file objects
• SRBFile file new SRBFile( fileSystem,
  /home/testuser.sdsc )
• LocalFile localfile
• new LocalFile( localParent, test.txt )

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The FileFactory Class

• The FileFactory class helps abstract away from a
  particular filesystem
• GeneralFileSystem fileSystem
• FileFactory.newFile( uri )
• GeneralFile file FileFactory.newFile(
  fileSystem, Test.txt )
• GeneralFile file FileFactory.newFile( uri )

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Common File Operations

• From the GeneralFile object, all the methods
  common to the java.io.File class are available,
  such as
• file.mkdir()
• boolean read file.canRead()
• String list file.list()
• Of course, SRB specific functionality requires an
  SRB declaration or casting the General object.
• ((SRBFile) file).replicate( )

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Reading and Writing a File

• The GeneralFile.copyTo( GeneralFile ) can be used
  to copy files to/from any supported file systems.
• Up/downloading using the SRB and a local system
• Large files will automatically use the SRBs
  parallel file transfer protocol.
• Directories will use the SRBs bulk load protocol.

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Reading and Writing a File

• GeneralRandomAccessFile supports random access
  (read, write, seek) matching java.io.RandomAccessF
  ile.
• GeneralRandomAccessFile raf
• FileFactory.newRandomAccessFile(
• file, "rw" )
• raf.write( new String( "This is a test.\n" ))
• File stream classes are also available.

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Query the file system.

• Queries are simplified from SQL.
• MetaDataCondition where
• MetaDataSet.newCondition(
• SRBMetaDataSet.OFFSET,
• MetaDataCondition.LESS_THAN, 999)
• MetaDataSelect select
• MetaDataSet.newSelection(
  GeneralMetaData.FILE_NAME )

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Query the file system.

• An array of the conditions and selections forms
  the query.
• MetaDataRecordList rl
• fileSystem.query( conditions, selects )
• MetaDataRecordList rl
• fileSystem.query( conditions, selects,
  numberOfResults, orderBy, nonDistinct )

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Retrieve the results

• Results from the query are return as a
  MetaDataRecordList rl
• rl0.getRecordCount()
• rl0.getIntValue(0)
• rl0.getValue(
• GeneralMetaData.FILE_NAME )

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Get further results from the query.

• By default a query will only return the first 300
  values.
• MetaDataRecordList methods are used to retrieve
  further results from the query.
• MetaDataRecordList getMoreResults()
• boolean isQueryComplete()

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Change the metadata of a file.

• Change the metadata with a new or existing
  MetaDataRecordList and send it to the file
  system.
• recordList.addRecord( SRBMetaDataSet.getField(
  SRBMetaDataSet.FILE_COMMENTS ),
• "new comments" )
• file.modifyMetaData( recordList )

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Query the definable metadata.

• Simliar to querying other metadata, but the
  MetaDataTable class is used instead of a scalar
  value.
• For example, finding files with user definable
  metadata matching
• aaa 123 AND bbb lt 456

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Query the definable metadata.

• String values aaa", "123",
  bbb", "456"
• int op
• MetaDataCondition.EQUAL, MetaDataCondition.L
  ESS_THAN
• MetaDataTable metaDataTable
• new MetaDataTable( op, values )

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Set the definable metadata.

• Setting the definable metadata is the same as
  other metadata.
• recordList.addRecord( SRBMetaDataSet.getField(
  SRBMetaDataSet.
• DEFINABLE_METADATA_FOR_FILES ),
  metaDataTable )
• file.modifyMetaData( recordList )

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Online Examples

• http//www.sdsc.edu/srb/jargon/
• Test.java
• MetaDataTest.java
• FactoryTest.java
• CopyTest.java
• Scommand-like examples
• And more

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Jargon as Scommands

• For those familiar with the
• Scommands, see Test.java for
• a non-exhaustive list of Scommands
• and their Jargon equivalent.

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Jargon Gui Components

• SRB and local files viewable in a single tree
• File metadata viewable and modifiable

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SRB Content Manager
Written by Daniel Moore
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Where to Get More Info

• http//www.sdsc.edu/srb/jargon
• iktome_at_sdsc.edu
• srb-chat_at_sdsc.edu