Evolution of the CERN Tape Archive Scheduling System

The CERN Tape Archive (CTA) scheduling system implements the workflow and lifecycle of archive, retrieve and repack requests. The transient metadata for queued requests is stored in the Scheduler backend store (Scheduler DB). In our previous work, we presented the CTA Scheduler together with an object-store backend implementation of the Scheduler DB. Now, with four years of experience in production, the strengths and limitations of this approach are better understood. While highly efficient for FIFO queueing operations (archive/retrieve), non-FIFO operations (delete, priority queues) require some workarounds. Additionally, this backend imposes constraints on how the CTA Scheduler code can be modified and is an additional software dependency and technology for developers to learn. This paper discusses an alternative Scheduler DB implementation, based on relational database technology. We include a status report and roadmap.