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Using services in DIRAC

Explore the usage of services in DIRAC by A. Tsaregorodtsev at the 2nd ARDA Workshop in June 2004. Learn about the production manager, job monitor, resources, user interfaces, and more at CERN. Discover GT3 attempts and other OGSI implementations discussed at the event.

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Using services in DIRAC

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  1. Using services in DIRAC A.Tsaregorodtsev, CPPM, Marseille 2nd ARDA Workshop, 21-23 June 2004, CERN LHCb week, 27 May 2004, CERN

  2. DIRAC Services and Resources User interfaces Job monitor Production manager GANGA UI User CLI BK query webpage FileCatalog browser BookkeepingSvc FileCatalogSvc DIRAC Job Management Service DIRAC services JobMonitorSvc InfomarionSvc MonitoringSvc JobAccountingSvc AccountingDB Agent Agent Agent DIRAC resources DIRAC Storage LCG Resource Broker DIRAC Sites CE 3 DIRAC CE gridftp bbftp DIRAC CE DIRAC CE DiskFile CE 2 CE 1 rfio LHCb week, 27 May 2004, CERN

  3. GT3 attempt • JobReceiver prototype Grid Service was done • Service gets jobs, checks its integrity and stores in the Job DB (MySQL) • Notifies Optimizers via Jabber • Uses Tomcat and GT3 LHCb week, 27 May 2004, CERN

  4. DIRAC WM architecture • Submit (JDL) • Status job Source job (JDL) WMS WMS Job LHCb week, 27 May 2004, CERN

  5. Globus Toolkit 3 (aka GT3) • What is GT3? The Globus implementation of OGSI • Really just the new version of Globus, prepared predominantly by Argonne National Labs (ANL) and IBM • Re-implements much of Globus Toolkit v2.4, but in Java • Based on Web Services, and runs from Tomcat Java Application Server LHCb week, 27 May 2004, CERN

  6. OGSI vs. GT3 Concepts Implementations OGSA – idea “Physiology of the Grid” Dirac Service GT3 – Globus OGSI implementation OGSI – formal standard (v1.0) Axis - Web Service framework Web Services – foundation for OGSI Tomcat – java application server LHCb week, 27 May 2004, CERN

  7. GT3 attempt results • GT3 is currently difficult to install, configure, and administer • took 2+ weeks to get GT3 fully installed and running properly • discuss@globus.org mailing list is full of similar stories • Service development and deployment is not straight forward • Must define GWSDL, WSDD, XML Schemas, etc. (don’t worry about acronyms) • Service performance is very low: • More than a minute to submit one job • Good news: Client side is not too complicated, and should be language independent. LHCb week, 27 May 2004, CERN

  8. Other OGSI Implementations • OGSI::Lite • Perl version developed at Manchester • pyGridWare • 100% python OGSI implementation • Currently: client maybe ready, server isn’t • We are interested because • Possibility of Ganga OGSI client • Expect it to be lightweight, easy to deploy, robust, and high performance MUST CONFIRM THESE EXPECTATIONS LHCb week, 27 May 2004, CERN

  9. XML-RPC protocol • Standard, simple, available out of the box in the standard python library • Both server and client • Using expat XML parser • Server • Very simple socket based • Multithreaded • Client • Dynamically built service proxy LHCb week, 27 May 2004, CERN

  10. File catalog service • The LHCb Bookkeeping was not meant to be used as a File (Replica) Catalog • Main use as Metadata and Job Provenance database • Replica catalog based on specially built views • AliEn File Catalog was chosen to get a (full) set of the necessary functionality: • Hierarchical structure: • Logical organization of data – optimized queries; • ACL by directory; • Metadata by directory; • File system paradigm; • Robust, proven implementation • Easy to wrap as an independent service: • Inspired by the ARDA RTAG work LHCb week, 27 May 2004, CERN

  11. AliEn FileCatalog in DIRAC • AliEn FC SOAP interface was not ready in the beginning of 2004 • Had to provide our own XML-RPC wrapper • Compatible with XML-RPC BK File Catalog • Using AliEn command line “alien –exec” • Ugly, but works • Building service on top of AliEn which is run by the lhcbprod AliEn user • Not really using the AliEn security mechanisms • Using AliEn version 1.32 • So far in DC2004: • >100’000 files with >250’000 replicas • Very stable performance LHCb week, 27 May 2004, CERN

  12. File catalogs AliEn FileCatalog Service FileCatalog Client AliEn FC Client AliEn FC AliEn UI XML-RPC server MySQL DIRAC Application, Service FC Client BK FileCatalog Service BK FC Client LHCb BK DB XML-RPC server ORACLE LHCb week, 27 May 2004, CERN

  13. FileCatalog common interface addFile(lfn,guid,size,SE<opt>,pfn<opt>,poolType<opt>) rmFile(lfn) rmFileByGuid(guid) addPfn(lfn,pfn,SE<opt>) addPfnByGuid(guid,pfn) removePfn(lfn,pfn) getPfnsByLfn(lfn) getPfnsByGuid(guid) getGuidByLfn(lfn) getLfnByGuid(guid) exists(lfn) existsGuid(guid) getFileSize(lfn) LHCb week, 27 May 2004, CERN

  14. Reliability issues • Regular back-up of underlying database • Journaling of all the write operations • Running more than one instance of the service • Configuration service running at CERN and in Oxford • Running services reliably: • Runit set of tools LHCb week, 27 May 2004, CERN

  15. Runit service management toolhttp://smarden.org/runit/ • Runit package features • Automatic restart on failure • Automatic logging of standard output with time/date stamps • Automatic log rotation • Cleanup scripts on process completion • Simple interface to pause, stop, and send control signals to services • Runs service in daemon mode • Can be used entirely in user space • Light-weight service management LHCb week, 27 May 2004, CERN

  16. Using Instant Messaging • Mechanism to pass messages across the network (ICQ, MSN, etc): • Asynchronous, robust • Client needs only outbound connectivity for bidirectional message exchange • Jabber as IM protocol • Open source, mature server implementation • Using XML for message formatting • Possibility to build a network of Jabber servers • Load balancing, proxies • Client API exists in many languages: • Python included LHCb week, 27 May 2004, CERN

  17. Using Instant Messaging (2) • Initially used for WMS components communication: • JobReceiver notifies Optimizers using Jabber • Monitoring of Agents • Using Chat Room paradigm where agents are updating their “presence” status • Possibility of broadcasting messages to agents • Monitoring Jobs • Jabber client running near the job • Access to the job std.out/err • Interactive control channel to the job LHCb week, 27 May 2004, CERN

  18. Using Instant Messaging (3) • Services communicating via IM protocol • XML-RPC over Jabber works just fine • Agents deployed on the fly on a computing resource can work as a fully functional service • With outbound connectivity only (no firewall problems) • Using this paradigm to run jobs on LCG now • Proxy for message passing is just a matter of yet another Jabber server • Client and server are keeping connection open • Authenticate once • Scalability issues • Problems when monitoring thousands of jobs LHCb week, 27 May 2004, CERN

  19. Conclusions • Building services from the existing components is rather easy; • Secure services is not easy • Having more than one implementation of services is a must; • Instant Messaging is very promising for creating dynamically deployed, light-weight services – agents. LHCb week, 27 May 2004, CERN

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