ExplainingApel

Context

Our CE is an HTCondor CE, and the underlying batch system is htcondor.

These CEs are equipped with an Apel software stack. The role of this machinery is to extract information about jobs from logfiles, and feed a local database with them. Everyday, the database is read, records are extracted from it and sent to a remote Apel accounting server.

From HTCondor job history files to batch and blah files

Each time a job is finished, a job record is created in the directory /var/lib/condor/history.

Thanks to a systemd timer (see /usr/lib/systemd/system/condor-ce-apel.timer), every hour, a script (/usr/share/condor-ce/condor_ce_apel.sh) is run to parse these history records and to generate the blah and batch files from them via the script /usr/share/condor-ce/condor_batch_blah.py. The blah and batch files are created in the directory /var/lib/condor-ce/apel. If for some reason, it fails to parse an history file, this file is moved to the subdirectory quarantine. Otherwise, it is removed.

After the blah and batch files have been generated, the script condor_ce_apel.sh will call /usr/bin/apelparser, a Python script whose role is to update the local Apel Mysql database with the content of the blah and batch files.