How to safely upgrade Bamboo and perform a rollback if needed?

Upgrading a Bamboo server safely depends on having a verified backup, applying the new binaries, and confirming that core functions such as plan execution, agent connectivity, and integrated tools operate as expected before declaring the upgrade successful. However, it is uncertain what specific verification criteria should trigger a rollback, how to ensure the backup itself is not corrupted or incomplete, and which early‑warning signals in startup logs or runtime metrics indicate a problematic upgrade.

What criteria should be used to decide that a rollback is necessary during the verification phase? How can backup integrity be validated prior to attempting a restore? Which logs, metrics, or health checks provide early detection of upgrade‑related failures that warrant a rollback?