1. GFAL: Grid File Access Library
Salvatore Scifo
INFN - Catania
Tutorial TriGrid su gLite 3.0 Catania,

2. SUMMARY This presentation covers the following points: 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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3. GFAL: Introduction What is GFAL for?
Grid storage interactions today require using some existing software components:
The replica catalog services to locate valid replicas of files in order to :
Download them to the user local machine
Move 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 software 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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4. 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 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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5. GFAL: File Names GFAL works with all Grid types name:
Logical File Name (LFN)
lfn:baud/testgfal15
Grid Unique IDentifier (GUID)
guid:2cd ae af6d-b1f
File Replica (SURL)
srm://wacdr002d.cern.ch:8443/castor/cern.ch/user/b/baud/testgfal
Transport file name (TURL).
rfio:////castor/cern.ch/user/b/baud/testgfal15
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6. GFAL: Environment Auxiliary linked libraries Environment Variables
libcgsi_plugin_gsoap_2.3
libglobus_gss
api_gsi_gcc32dbg
libglobus_gss_assist_gcc32dbg).
Environment Variables
LCG_GFAL_VO
LCG_GFAL_INFOSYS
LCG_CATALOG_TYPE
LCG_RFIO_TYPE
LFC_HOST
LD_LIBRARY_PATH
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7. GFAL: Available API C API Java API (C API Wrapper)
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.
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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8. GFAL References Examples in gLite3 User Guide (Appendix F)
GFAL C API Description:
GFAL JAVA API
GFAL Java API code and libraries:
On-line JavaDoc of Java API:
GFAL Excercises (C/Java):
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