Speaker
Description
The ATLAS experiment is redesigning its Conditions database infrastructure in preparation for Run 4. The new system (CREST - Conditions REST) adopts a multi-tier architecture in which interactions with all databases including the Trigger physics configuration database are mediated through a web-based server layer using a REST API. The data caching is provided via Varnish HTTP proxies. We present the current status of the associated software and infrastructure developments, illustrating progress through concrete workflow examples ranging from High-Level Trigger (HLT) usage to Monte Carlo Upgrade simulations for Run 4.
To validate performance and functionality, a dedicated demonstrator has been developed for a typical HLT workflow. This workflow poses unique challenges compared to later data-processing stages, as it requires both efficient data caching and rapid updates of frequently changing conditions, such as luminosity and beamspot parameters, during raw data processing. We describe the demonstrator setup along with results from performance and scalability tests.
Finally, we outline the migration strategy from the current COOL conditions database to CREST system, which enables large scale validation using HLT reprocessing, data reprocessing, and Monte Carlo simulation workflows. This represents a key milestone toward certifying a grid-ready Conditions database service and ensuring full compatibility across the experiment’s software ecosystem for HL-LHC operations.