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SVN Pilot: CVS Replacement

SVN Pilot: CVS Replacement. Manuel Guijarro Jonatan Hugo Hugosson Artur Wiecek David Horat Jonathan Brugge Michel Manent September 2008. Outline . Introduction Motivation Subversion Objectives Performance Tests Security Implementation Questions. Version Control Systems.

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SVN Pilot: CVS Replacement

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  1. SVN Pilot: CVS Replacement Manuel Guijarro Jonatan Hugo Hugosson Artur Wiecek David Horat Jonathan Brugge Michel Manent September 2008

  2. Outline • Introduction • Motivation • Subversion • Objectives • Performance Tests • Security • Implementation • Questions 2

  3. Version Control Systems • Maintain current and historical versions of files and data (source code) • There are many commercial and Open Source VC Systems: • (Centralised) CVS/SVN • (Distributed) GIT, Bazaar, Darcs, GNU arch, Mercurial, Monotone, etc • But subversion seems to be the most popular one (used by GCC, Phyton, PuTTY, Apache, GNOME, KDE, etc) • Physics User Community: (IN2P3, ROOT, Totem..) 3

  4. CERN Central CVS Service • Hosts over 330 Software Projects • 29 for Atlas • 46 for CMS • 8 for LHCb,….. • Over 3000 developers registered • Over 90 GBytes of source code • Creates 250 Remedy tickets per year • Over 100000 commits per month 4

  5. CERN Central CVS Service

  6. Central CVS service features • High Availability and Load Balancing • Web interface to repositories • Usage Statistics • Repository Remote Replication + Mirroring • Daily archive of Repositories and DR • Developers Mailing list • Pre/Post Commit Actions (such us e-mail notification, etc) • Various access method (ssh/kerberos) • Role split (CVS Admin/Librarian/Developer) 6

  7. Motivation for SVN Pilot • Originally designed to host less than 100 projects • Requests to provide a central SVN service: • From CMS • From ATLAS (case study in 2006) • And from many others • CVS is over 20 years old while SVN is this millennium technology • Requests for Read Access control

  8. SVN vs. CVS 8

  9. New Features (SVN 1.5) • Automatic update of working copy • Merge tracking • Subversion keeps track of what changes have been merged where • Sparse checkouts • Interactive conflict resolution 9

  10. Pilot Objectives • Provide current CVS service features • Add new features (available with SVN) • Control Read access per path (module) • Authenticated Web access • Binary files handling • Ease CVS to SVN migration • Improved usage statistics (SVN Stats) • Handling of first line support via the Help Desk • Delegate administrative tasks to Software Librarians of each project • Prevent uncontrolled setup of SVN servers • Manpower: 1.2 FTE project

  11. Timetable 11

  12. SVN Pilot study • Access methods • https • ssh • Shared storage • NFS 3/4 • AFS • Securing service • Restricted Shell • Chrooted hooks (commit scripts) • Infrastructure: • Librarian tools, Statistics, Web Interface,… 12

  13. Performance Tests • SVN check out of a 110 Mb project • Parameters • AFS/NFS3/NFS4 • HTTPS/SSH 13

  14. AFS vs NFS3 (1 server) 14

  15. AFS vs NFS4 (1 server) 15

  16. AFS vs NFS4 (3 servers) 16

  17. Preliminary Conclusions • AFS much faster than NFS • SSH much faster than https • SSH scales very well with high load • … • New tests ongoing (with mixture of read and write operations) 17

  18. Security • Project Isolation • Windows/Linux clients • Worldwide access • Shared file system independent • Hooks executed on servers • Librarians may put any script into the hooks • Librarians might need file system level access to repository – being studied Security risk!! 18

  19. Hooks (scripts) Client Server Svn commit Pre-commit hook is executed Post commit hook is executed SVN: Commit OK Email notification recieved 19

  20. Hook scripts chrooted: Server svnserer Librarian hooks: jailed hooks/post-commit hook Usr-hooks/post-commit hook Repository (1) Repositories System files 20

  21. Architecture • svn.cern.ch (rw) • Secured subversion server (only ssh) • Read and write access to repository • svnweb.cern.ch (ro) • User documentation • Project request • SVN web interface • Usage statistics 21

  22. Pilot Implementation Summary • SSH access for SVN clients • Restricted shell for all SVN clients • Hooks chrooted • SVN web (ro) • Web interfaces: websvn, trac • SSO Authenticated access • Administration delegated to librarian • Access rights • Hooks • Admin tools 22

  23. Conclusions • Secure service • This will replace CVS by end of 2009 • The service is supported (pre-production) • Pilot setup may differ from final setup • Access method, Web interface, shared file system, etc. • Changes will be transparent to the users 23

  24. Support http://cern.ch/svn • Try the pilot • Documentation Svn.support@cern.ch 24

  25. Questions? Thanks For Listening…. M. Guijarro, A. Wiecek, David Horat, Jonathan Bugge, M. Manent, H. Hugosson 25

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