[Clas_offline] CLAS_PACK and clasdb, again

[Nathan Baltzell]

Hi All,

Now we have another clasdb.jlab.org issue, this time with too many connections to the server.
This problem recently became exasperated after batch farm upgrades allowed us to run more
simultaneous jobs, while clasdb cannot handle so many simultaneous connections.  It is affecting
rungroups reconstrucing real data for analysis, simulation jobs, clas wikis, shift database, etc …
Probably the server will be upgraded soon, but we should address the issue on our side too by
getting rid of persistent connections.

All users should implement this change in their code if you are running or plan to run many
simultaneous jobs on the batch farm.  This is known to be an issue in user_ana, but it could
also be anywhere that uses CLAS's libcaldbMap.  If you are currently running many batch
farm jobs with persistent connections, you should at least implement this change and recompile
ASAP before allowing any more jobs to run:

caldb/Map/calib_disconnect.c
Uncomment the "mysql_close(&mysql)".
This one-liner fix is now in CVS and SVN, and it has the effect of closing every connection
after the query is done.  Subsequent queries will automatically reconnect and disconnect,
leaving no persistent connections.

HOWEVER, you must also have the previous fix of correcting the test of mysql_ping
in caldb/Map/calib_connect.c, which is also in both repositories, in order for this new
fix to work:

https://mailman.jlab.org/pipermail/clas_offline/2014-September/000874.html

-Nathan