1. Clara Gaspar, November 2002 DIM As DIP candidate

2. Clara Gaspar, November 2002 2 DIM’s philosophy zPublish/Subscribe (client/server) zServices ySingle items, arrays or structured data yFree name space (should be hierarchical and well defined for DIP) yCan be time-stamped (and have a quality flag) zName Server ykeeps the coordinates of available services

3. Clara Gaspar, November 2002 3 DIM Dataflow zInternal mechanism

4. Clara Gaspar, November 2002 4 DIM’s functionality zPublisher yDeclares Services yCan update services on change zSubscriber yCan subscribe on change or on time basis or both (+ current value). yCan execute a “callback” when new data arrives. yWill be informed when data not available

5. Clara Gaspar, November 2002 5 Client Error handling zClient error notification (callback) yQuality flag from Server yTimeout for periodic services and for on change with timeout yServer (or it’s machine) down zClient error recovery yAutomatic reconnection when: xServer up (also if it moved to a new machine) xName Server restart (also if it moved) zNote: Any pre-established connections will continue working without DNS

6. Clara Gaspar, November 2002 6 Server Error Handling zServer error detection and recovery yAutomatic disconnection from a “blocked” client (the client will automatically reconnect if it comes back) yAutomatic (re)declaration of services when Name Server (re)starts zName Server yServers have a watchdog mechanism A hanging server will automatically be “removed” from the system yA server trying to publish an existing service will be killed (service names must be unique)

7. Clara Gaspar, November 2002 7 Dynamic Behaviour Summary zServers yCan declare and un-declare services dynamically yCan be started/restarted anywhere anytime zClients yCan subscribe or un-subscribe dynamically yWill be informed in case of errors zName Server yCan be restarted (in a different machine)

8. Clara Gaspar, November 2002 8 DIM Availability zDIM is available under GPL (GNU Public License) yAs Server and Client libraries: xAPI: C, C++ and Java (needs integration) xat http://www.cern.ch/dim yFor the platforms: xVMS (VAX and APHA) xUNIX flavours (HP-UX, Sun-OS, Sun-Solaris, IBM-AIX, DEC-OSF, Linux) xWindows NT/2000 xReal-time OSs (OS9, LynxOS, VxWorks)

9. Clara Gaspar, November 2002 9 Usage zDelphi y> 35000 services y450 servers y60 machines (VMS and OS9) zL3 and L3 cosmics yFor exchanges between: UNIX (hp-ux, solaris, linux),VMS (vax and alpha), LynxOS and OS9 zBabar, fixed target exps. and several LHC exp. sub-systems (Linux, Windows and Solaris)

10. Clara Gaspar, November 2002 10 Usage  Skyguide recently “bought” DIM yLarge number of heterogeneous systems: xRadars, Radar trackers, multi-radar computers, radar displays, radio switches, radio transmitter and receivers, flight plan systems, navigation aids, telephone switches, legal recording, environmental information system, international communication systems, infrastructure, … xSome systems have been bought, some other developed by skyguide, all with different technologies. xUntil now, each system had its own supervision console  Needed to exchange information for global supervision -> DIM & PVSSII

11. Clara Gaspar, November 2002 11 DIM Browsing/Monitoring zLarge distributed systems are normally difficult to Test, Debug and Monitor zDue to the DIM publishing mechanism: yDIM components (the Name Server and the Servers) publish a set of standard Services used for monitoring yA tool - DID - (using the standard DIM client API) allows access to all information yA specialized browsing API is also available Can ask for “LHC/magnets/*/current” and then subscribe

12. Clara Gaspar, November 2002 12 DIM Browsing - DID

13. Clara Gaspar, November 2002 13 DIM Performance Fast Ethernet (100Mb/s) Gigabit Ethernet (1000Mb/s) Throughput (kB/s) Message Size (bytes)

14. Clara Gaspar, November 2002 14 DIM Performance results

15. Clara Gaspar, November 2002 15 DIM example

16. Clara Gaspar, November 2002 16 DIM as DIP yThe DIM API could almost directly become the DIP API yA small layer could be written on top to adapt to any new features: xDimService -> DipTopic xDIP data format xSome form of security/authentication (none in DIM) yEach domain would then use the DIP API to publish/subscribe to data

17. Clara Gaspar, November 2002 17 Proposals zData Format yWhy not leave it free? It’s a “contract” between publisher and subscribers xSome data could be XML xSome could be structures (time stamp, etc.) xBrowsing tools could help checking (offline) zSecurity/Authentication yWhat do we want to protect against? xNo commands, so no problem there... xNot twice the same service xIf no client is interested no traffic Do we need more?