Thanks for the email.

This is a discussion that should be shared on the hps-software mailing list, as there are several people working with this more closely that should be in the loop, namely Matt, Sho, and Omar.  Maurik should also be aware of this because he's in charge of the HPS software effort.  I've added all of these people and the list to this message.

My opinion is that a MySQL database is overly complicated for what we're currently doing, and I don't see anyone needing anything like this for now.  Recently a bunch of files were removed from the hps-detectors CVS, which is the source for HPS conditions, and put into the resources area of the hps-java project where they can be accessed as plain old Java resources.  This data was from the test run, and reason for doing this was that the conditions had to all be copied between the different detector model directories to be accessed, which, as you can imagine, involves an enormous amount of data duplication.  And many of these data sets are being used to analyze ALL data from the test run across all runs, so putting them into a conditions system by run or time does not make that much sense.

The problem with a database, as I see it, is that the user either has to run this themselves on their local machine, which is an extra amount of installation and setup, OR there has to be a shared instance that hps-java accesses, especially for jobs run on batch farms or the grid.  (The database also has to be kept up to date, which is more complicated than the current method of 'cvs up' to get new text files.)  Either one of these working methods could cause problems with how we currently do things.  For one, many batch systems are not that friendly when it comes to connecting out to databases unless this is preconfigured by their admins to allow it.  And having users run their own MySQL database just strikes me as an unnecessary headache.  We already have enough troubles getting people to install and run the software on their own machines, and this would add another hurdle that frankly isn't necessary right now.

For the analysis of test run data and for the foreseeable future, we are fine in terms of LCSim infrastructure in this area, in my opinion.  Given that the next HPS "run" is not going to be for several years, at least, as the JLab schedule was pushed back, I'd like to see attention focused elsewhere, namely on JAS/AIDA development.  

We've started to collect a list of requested features and bug fixes here.

What you added to the current conditions system for accessing databases should be fine, at least for people just to play around with and experiment.  There isn't anything on that list having to do with conditions, but people can add it if they wish or see the need.  To me, the need for this kind of "proper" conditions system with run/time tagging and a database backend is just so far into the future that it is practically irrelevant right now.

That's mostly just my opinion though.  I wonder if others have anything to add to the discussion...?


-----Original Message-----
From: Onoprienko, Dmitry 
Sent: Friday, September 14, 2012 11:24 AM
To: Neal, Homer A.; Johnson, Tony; McCormick, Jeremy I.; Graf, Norman A.; Nelson, Timothy Knight
Subject: HPS conditions framework

Hello Everyone,

I just want to touch base regarding the HPS use of org.lcsim conditions framework.

A few months ago, I was asked by Tony (the original request came from Homer I believe) to modify the framework and enable reading conditions from MySQL database instead of a zip file. I was also asked to make it possible for conditions to be run-dependent. Since HPS was preparing for the beam test at that time, Norman and Jeremy stressed the importance of keeping changes to org.lcsim code to absolute minimum. I also found that HPS was already using the conditions framework in the traditional way - getting data from zip files - so that capability had to be preserved.

Given these constraints, I made a few minor changes to standard implementations on ConditionManager and ConditionsReader, and created a hook that can be used to load experiment-specific conditions reader. The changes are backward compatible and transparent to the user - the framework will still look for a conditions archive or directory with a name derived from the detector name it finds in the org.lcsim event. However, if the file in that archive contains a line in
"ConditionsReader: <ClassName>" format, the framework will instantiate <ClassName> class and use it in place of the standard reader.

There is an example of use in org.lcsim.hps.conditions package (hps-java project, see package javadoc for instructions on how to run it). Since we knew nothing about the structure of the actual HPS conditions data, the example is just a trivial demo that shows how to fetch something from a database and retrieve it through the conditions framework.

Now that people seem to be actually using conditions, I wonder if it's time to take the next step. Is the scheme of loading a custom conditions reader through an entry in the file convenient ? There are alternatives that would make the framework behavior a bit more transparent at a price of requiring more substantial changes to the codebase. Is anyone familiar with HPS data interested in working with me to get some more realistic conditions into the database ?

Best Regards,
- Dmitry.

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