Unified Experiment Monitoring

The Unified Experiment Monitoring (UEM) is the project in WLCG with the objective to harmonize the WLCG job accounting reports across the LHC experiments, in order to provide aggregated reports of the compute capacity used by WLCG as a function of time. This accounting overview of all LHC experiments is vital for the strategy planning of WLCG and therefore it finds the strong support of the LHC Experiments Committee (LHCC). However, creating common overviews is challenging, due to the different internals of each experiment monitoring system and also due to the long time-scale of the reports to cover at least a decade of data. These monitoring systems evolved largely independently over time, implying that the UEM project has to design and implement different approaches to couple the multiple data sources within the CERN IT monitoring tools which will be used. Last but not least, the different terminologies have to be aligned into a useful and coherent set. This contribution summarizes the motivations of the project, the challenges faced, the design adopted to overcome them, and the presentation of the state of the art.