Stability of the CMS Submission Infrastructure for the LHC Run 3

The CMS Submission Infrastructure is the main computing resource provisioning system for CMS workflows, including data processing, simulation and analysis. It currently aggregates nearly 400k CPU cores distributed worldwide from Grid, HPC and cloud providers. CMS Tier-0 tasks, such as data repacking and prompt reconstruction, critical for data-taking operations, are executed on a collection of computing resources at CERN, also managed by the CMS Submission Infrastructure. All this computing power is harnessed via a number of federated resource pools, supervised by HTCondor and GlideinWMS services. Elements such as pilot factories, job schedulers and connection brokers are deployed in high-availability mode across several ``availability zones'', providing stability to our services via hardware redundancy and numerous failover mechanisms. Right before the start of the LHC Run 3, the Submission Infrastructure stability was tested in a series of controlled exercises, performed without interruption of our services. These tests demonstrated the resilience of our systems, and additionally provided useful information in order to further refine our monitoring and alarming system. This report will describe the main elements in the CMS Submission Infrastructure design and deployment, along with the performed failover exercises, proving that our systems are ready to serve their critical role in support of CMS activities.