[Halld-offline] CCDB access at JLab changed to MySQL database by default

[Mark Ito]

Folks,

This morning, as I mentioned earlier, we had a problem accessing 
anything from our webserver, halldweb.jlab.org. You may be aware that 
other webservers and functions around the Lab were affected including 
www.jlab.org. Turns out this was due to a large number of farm jobs 
trying to copy the RCDB in its SQLite form onto the local disk of the 
farm node. This was being done to avoid overloading the MySQL database 
server. Unfortunately, it caused problems lab-wide.

*We have decided to go back to using the MariaDB database server 
(hallddb.jlab.org) as the default choice for CCDB and RCDB, rather than 
the SQLite file.* The default is set by the gluex_env_jlab.(c)sh script. 
Folks who over-ride the defaults will continue to over-ride the 
defaults, of course. The change has been made on the scripts and 
installed in /group/halld/Software/build_scripts.

In the past we have said that farm jobs should use the SQLite form of 
the CCDB and changed the default to align with that recommendation. That 
got us out of the situation of farm jobs using up all of the available 
connections on the database server. This change is indeed a reversal and 
may expose us to such incidents going forward.

The idea is to go back to the original configuration and study problems 
as they arise in more detail than we have in the past. This avoids 
having our farm jobs interfere with computing activities at the Lab 
outside Hall D immediately. It should also enable us to systematically 
craft a effective long-term fix. Dmitry Romanov is on-site now and has 
agreed to help us with solutions.

   -- Mark


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