Speaker
Sergey Kalinin
(Universite Catholique de Louvain)
Description
As the Large Hadron Collider (LHC) at CERN, Geneva, has begun operation in
September, the large scale computing grid LCG (LHC Computing Grid) is meant
to process and store the large amount of data created in simulating,
measuring and analyzing of particle physic experimental data. Data acquired
by ATLAS, one of the four big experiments at the LHC, are analyzed using
compute jobs running on the grid and utilizing the ATLAS software
framework 'Athena'. The analysis algorithms themselves are written in C++ by
the physicists using Athena and the ROOT toolkit.
Identifying the reason for a job failure (or even the occurance of the
failure itself) in this context is a tedious, repetitive and - more often than not -
unsuccessful task. The debugging of such problems was not foreseen and tracing back problems is even more difficult by the fact that the output-sandbox,
which contains the jobs' output and error logs, is discarded by the grid middleware if the job failed. So, valuable information that could aid in finding the failure reason is lost. These issues result in high job failure
rates and less than optimal resource usage.
As part of the High Energy Particle Physics Community Grid project (HEPCG)
of the German D-Grid Initiave, the University of Wuppertal has developed the
Job Execution Monitor (JEM). JEM helps finding job failure reasons by two means: It periodically provides vital worker node system data and collects jobrun-time monitoring data. To gather this data, a supervised line-by-line
execution of the user job is performed. JEM is providing new possibilities
to find problems in largely distributed computing grids and to analyze these
problems in nearly real-time.
All monitored information is presented to the user almost instantaneously
and additionally stored in the jobs' output sandbox for further analysis. As a
first step, JEM has been seamlessly integrated into ATLAS' and LHCb's grid
user interface 'ganga'. In this way, submitted jobs are monitored transparently, requiring no additional effort by the user.
Author
Sergey Kalinin
(Universite Catholique de Louvain)
