1. GFAL Grid File Access Library
Salvatore Scifo
INFN - Catania
Tutorial per utenti Palermo, Dicembre 2007

2. SUMMARY This presentation covers the following points: GFAL Overview
GFAL Available APIs
GFAL C API Overview
GFAL Java API Overview
GFAL References
GFAL C API Practical (hands on session)
GFAL Java API Practical (hands on session).
Tutorial per utenti - Palermo (Italy), Dic 10th - 12th 2007

3. GFAL: Introduction Grid Data Management System
FTS - File Transfer Service
Basic service to move files to/from Storage Elements
File Catalog
Keep trace about the location of files with in the distributed FS
Replicate files on several sites
Make job running on the worker node able to discover and take files stored on remote storage element.
SRM – Storage Resource Manager
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)
Many other functions…
Metadata Catalog
Associate descriptive attributes to file
Database virtualization (simple schemas)
Tutorial per utenti - Palermo (Italy), Dic 10th - 12th 2007

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 of low level protocols (dCache, CASTOR, …)
Fully compliance with the GSI (Grid Security Infrastructure), interaction to SRM in secure mode.
Tutorial per utenti - Palermo (Italy), Dic 10th - 12th 2007

5. GFAL: File Names GFAL works with all Grid types name:
Logical File Name (LFN)
lfn:/grid/cometa/tutorial/testgfal.dat
users level usage
Grid Unique IDentifier (GUID)
guid:/2cd ae af6d-b1f
basic services level usage
Site URL (SURL)
srm:/wacdr002d.cern.ch:8443/castor/cern.ch/user/b/baud/testgfal
replica management level usage
Transport URL (TURL).
rfio:/castor/cern.ch/user/b/baud/testgfal15
SE transfers levele usage
Tutorial per utenti - Palermo (Italy), Dic 10th - 12th 2007

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
Tutorial per utenti - Palermo (Italy), Dic 10th - 12th 2007

7. GFAL: Available APIs C API -> functions oriented
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) -> Object Oriented
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)
Tutorial per utenti - Palermo (Italy), Dic 10th - 12th 2007

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):
Tutorial per utenti - Palermo (Italy), Dic 10th - 12th 2007

9. Than you very much for your kind attention!
Questions…
Than you very much for your kind attention!
Tutorial per utenti - Palermo (Italy), Dic 10th - 12th 2007