The ATLAS Event Monitoring Service - Peer-to-Peer Data Distribution in High Energy Phyisics

The ATLAS Event Monitoring service (Emon) is a CORBA-based Peer-to-Peer data distribution framework, which has been implemented for CERN's forthcoming particle physics experiment ATLAS. Its purpose is to sample collision events from various stages of the data flow chain and efficiently distribute them to the users. Starting from a centralized predecessor version, this paper discusses various technical details of the current implementation along with a comparative study of communication complexity and scalability and a presentation of practical test results obtained during the HLT/DAQ large scale and performance test period in July 2005. Apart from that, a recent addition allowing users the parallel analysis of event data will be presented.