Gratia is an accounting system used in OSG. At each grid site it gathers usage information from the local batch system using a _probe_ that is specific to the type of batch system being used. -So for example on the gatekeeper for a site running Condor, the HTCondor probe will be run out of cron every so often. When it runs, it queries HTCondor's history as maintained by the SchedD and for each newly completed job it finds it will take usage information out of that job's ClassAd, reformat it into a Gratia _usage record_, and send it to the Gratia database. +So for example on the gatekeeper for a site running HTCondor, the HTCondor probe will be run out of cron every so often. When it runs, it queries HTCondor's history as maintained by the SchedD and for each newly completed job it finds it will take usage information out of that job's ClassAd, reformat it into a Gratia _usage record_, and send it to the Gratia database. The Gratia probe for HTCondor was initially developed at Fermi. In its initial implementation it worked by scanning a directory for user log files for jobs run via GRAM. These user log files were generated via a patched version of the HTCondor job manager for GRAM. For any eviction record or completion record found in these log files, the probe would then use condor_history to get full details for the given job and send a record to Gratia. There were a few drawbacks to this approach, most significantly the potential for lost records and the common occurrence of duplicate records.
