Version control and DevOps for accelerator and experiments: experience and outlook

GitLab has been in operation at CERN since 2012. It is a self-service code hosting application based on Git that provides collaboration and code review features, becoming one of the key infrastructures at CERN. It is extensively utilised at CERN, with more than 17 000 active users, hosting more than 120 000 projects and triggering more than 5 000 jobs per hour. During the initial stages, a custom-made solution was deployed. However, with the exponential increase of projects, workflows, and continuous integrations, the GitLab infrastructure became hard and complex to scale and maintain. The recent migration, which involved adopting a new supported Cloud Hybrid infrastructure, has enabled CERN to align its GitLab infrastructure with industry standards and best practices. This has resulted in a significantly more robust and high-performing infrastructure, leading to notable benefits throughout the entire deployment process. This paper will address how this deployment process, on the road to success, has presented a series of challenges and pitfalls that have been faced during this complex migration process.