FWWG

Wednesday 26 Mar 2008, 14:00 → 16:00 Europe/Zurich

14/4-002

Present: Jim, Olivier (Pisano), Fernando (Lucas), Lennart, Peter, Manuel, Clara, Carmen, Svetozar, Dirk, Fernando Varela, Francisca, Frank, Piotr, Wayne 1) News Piotr reported that the Qt 3-D viewer is nearing completion to the level of functionality provided by the CMS Java implementation and that this would be presented at a future meeting. Wayne asked about the possibility to organize a meeting to discuss web access to PVSS data. ALICE requested that this not take place before the week of the 21st April. 2) External Access to PVSS Archive Data Piotr presented the proposed functionality as described in Twiki: https://twiki.cern.ch/twiki/bin/view/Controls/OracleArchiverExternalAPIRequirements There are two types of function foreseen; Query and Management. These would be implemented in PLSQL functions in the database such that they could be called from any application in any language. There was a discussion as to whether a higher level API should be provided in the most popular language e.g. C++ or Java. There seemed to be a wish for this although it was not clear which language was the most used - C/C++, ROOT (C++), Java, Coral, Python. Of the four Query functions the first (getHistory) seems to be the most important and certainly the highest priority. Of the two management functions the second (getSystemInfo) seems to have a slightly higher priority than the first but still fairly low. The following points were raised: - The getHistory function foresees to be able to use dpName, dpAlias or dpComment. There was a question as to whether the dpComment would be unique. This is only really requested for ATLAS and they have a policy to ensure that these are unique within a PVSS system. As the system name has to be given in this function, then it should be ok. - Although the function requires the system name it is clear that the final application given to the end user should not require this knowledge of the end user but rather should hide this complexity. - Is it necessary to retrieve dynamic arrays? Yes, at least for LHCb. - Is the 'bonus parameter' required? Yes. - Should the getTimestamps function allow AND conditions? No, this should be implemented at the level of the client application as it is not possible to standardize this in an easy way. - However, in general what can be implemented in the database should be as the database is not likely to be CPU-limited. Nonetheless, this should be considered carefully to make sure that it makes sense from the overall end-to-end point of view. - The getReducedHistory function may in fact be of interest to ETM as a way of improving the performance and robustness of the trending tool. To be followed up with Martin Koller. - It was stressed that measures would need to be taken to protect the database from overloading. Manuel noted that certain possibilities exist at the level of the DBA. Another possibility is to follow the approach adopted by ALICE with AMANDA. Essentially there is a single server which accesses the database and all clients requesting data do so via this server. In this way measures to limit the load on the database can be implemented in this server. - Peter noted that to avoid the low performance when using the 'bonus parameter' in ALICE, the archive bit is toggled at the start of a run to ensure a valid value is available with that timestamp in the database. - There was a discussion as to whether such functions required for external applications were not also required within PVSS. It was agreed that they should be available in PVSS and that a generic way to call any PLSQL function in the database from PVSS was required. Manuel stated that this would be straightforward. There was then a discussion on whether a generic tool at a higher level would be desirable and possible. ATLAS has 5 plotting tools, although two seem to be more generic and popular; one based on ROOT and the second, the PVSS Data Viewer - a Java trending-type tool. It was agreed to review these and others in ALICE and CMS at a future FWWG meeting towards the end of April.