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

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.

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)

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.

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

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

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.

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)

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:

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/grid- deployment/documentation/LFC_DPM/gfal/html/

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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