GFAL
Grid File Access Library
Annamaria Muoio
INFN Catania
I Corso di formazione INFN su aspetti pratici
dell'integrazione di applicazioni in GRID
Martina Franca, 13/11/2007
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SUMMARY
• This presentation covers the following points:
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GFAL Overview
GFAL Available APIs
GFAL C API Overview
GFAL Java API Overview
GFAL C API Practical (hands on session)
GFAL Java API Practical (hands on session)
GFAL References.
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GFAL: Introduction
• What is GFAL?
– It stands for Grid File Access Library!
– Grid storage interactions today require using some existing
software components:
– The file catalog services to locate valid replicas of files in order to
• Download them to the user local machine
• Copy them from a SE to another one
• Make job running on the worker node able to access and manage
files stored on remote storage element.
– The SRM to ensure:
• Files existence on disk or disk pool (they are recalled from mass
storage if necessary)
• Space allocation on disk for new files (they are possibly migrated
to mass storage later)
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GFAL: Main features
• The GFAL Features
– Hides interactions to the SRM to the end user
– Provides a Posix-like interface for File I/O Operation
– Based on shared libraries (both threaded e unthreaded version)
– Needs only one header file (gfal_api.h) to write C applications
– Supports following protocols :
file for local access nfs-like
dcap, gsidcap and kdcap for dCache access protocol
rfio for CASTOR/DPM access protocol.
– Access to SRMs in secure mode, i.e. using a valid Grid proxy
obtained by voms-proxy-init command.
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GFAL: File Names
• GFAL works with all Grid types name:
– Logical File Name (LFN)
lfn:baud/testgfal15
– Grid Unique IDentifier (GUID)
guid:2cd59291-7ae7-4778-af6d-b1f423719441
– File Replica (SURL)
srm://wacdr002d.cern.ch:8443/castor/cern.ch/user/b/baud/testgf
al
– Transport file name (TURL).
rfio:////castor/cern.ch/user/b/baud/testgfal15
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GFAL: Environment
• Auxiliary linked libraries
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libcgsi_plugin_gsoap_2.3
libglobus_gss
api_gsi_gcc32dbg
libglobus_gss_assist_gcc32dbg.
• Environment Variables
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LCG_GFAL_VO
LCG_GFAL_INFOSYS
LCG_CATALOG_TYPE
LCG_RFIO_TYPE
LFC_HOST
LD_LIBRARY_PATH
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GFAL: Available API
• C API
– The header file gfal_api.h needs to be included in the
application source code to get the prototype of the functions.
– The function names are obtained by prepending gfal_ to the
Posix names, for example gfal_open, gfal_read, gfal_close ...
– The argument lists and the values returned by the functions
are identical.
– The variable errno is set to the Posix Error Codes in the
case of failure.
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GFAL: Available API
• Java API (C API Wrapper)
– It provides three main Java Objects that need to be imported
in the java applications in order to hide the underlying C
functions.
GFalFile : to handle and read/write files
GFalDirectory : to handle and manage directories (create,
delete, list)
GFalUtilities : to manage file (rename, stat, lstat, delete)
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GFAL Java API
• GFAL API are available for C/C++ programmers
• We wrote a wrapper around the C APIs using Java
Native Interface and a the Java APIs on top of it
• More information can be found here:
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GFAL References
• Examples in gLite3 User Guide (Appendix F)
– https://edms.cern.ch/file/722398//gLite-3-UserGuide.pdf
• GFAL C API Description:
– http://grid-deployment.web.cern.ch/griddeployment/documentation/LFC_DPM/gfal/html/
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Evento, Luogo, Data odierna - 11
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Hands on
http://repository.gs.ba.infn.it/twiki/bin/view/GILDA/APIGFAL
http://repository.gs.ba.infn.it/twiki/bin/view/GILDA/APICGFAL
http://repository.gs.ba.infn.it/twiki/bin/view/GILDA/UsingGFAL
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