Post mortem: A bug from the past

In a post-mortem analysis, Ivar Conradi Østhus discusses a bug that affected Unleash, an open-source feature management tool, when a user encountered issues after upgrading from version 3.17.6 to 4.4.4. The problem originated from an incomplete database migration file mistakenly included in version 3.13.0, which did not manifest as an issue until the upgrade to version 4 exposed it. This incomplete migration was inadvertently left in the release due to a caveat of using TypeScript, where files not processed by the compiler were not removed from the distribution folder. The Unleash team resolved the issue by creating a new migration to correct the database state and implemented process improvements to prevent future occurrences, such as clearing the distribution folder before building releases and shifting the release process to a GitHub action rather than local developer machines. This approach enhances reliability and simplifies the release process for new team members, ensuring a more consistent and error-free release pipeline.