When performing an upgrade of an application, it may be desirable to fully stop the deployment at any sign of an error. A partially upgraded system with mixed versions may not work at all, so continuing with part of the infrastructure while leaving the failed systems behind can lead to big problems. Fortunately, Ansible provides a mechanism to decide when to reach a fatal error scenario.
By default, when Ansible is running through a playbook and encounters an error, it will remove the failed host from the list of play hosts and continue with the tasks or plays. Ansible will stop executing either when all the requested hosts for a play have failed, or when all the plays have been completed. To change this behavior, there are a couple of play controls that can be employed. Those controls are any_errors_fatal and max_fail_percentage.