DuplicateJobs cookies can fail to get deleted when upgrading to 15.6
Recently we changed the format of the Redis data stored by the DuplicateJobs Sidekiq middleware: gitlab-com/gl-infra/scalability#1954 (closed). In GitLab 15.6, the new format got enabled for self-managed via !102646 (merged).
In gitlab-com/gl-infra/scalability#1954 (comment 1236430898) we learned this can cause problems for zero-downtime upgrade to 15.6. Some Sidekiq cronjobs fail to get scheduled for 6 hours. This happens when an old (pre-15.6) Sidekiq process picks up a job scheduled by a 15.6 Sidekiq process.
We have found a workaround for this problem. This issue is for tracking the problem and the shipping of the workaround.
Edited by Jacob Vosmaer