Never Take the Whole Tier Down

Batch a rollout so at least one web server is always in service.

A advanced Ansible challenge worth 20 points. Solve it hands-on in a real Ansible environment in your browser - no local setup, no fake shells.

The Challenge

Scenario: Post-incident 6120 - the 09:40 deploy took the entire web tier offline for forty seconds because both nodes drained at once.

Turn it into a real rolling update: an independent monitor samples both nodes' health files throughout the run and both must never be out of service simultaneously. Both must finish on 4.2.0 and healthy, and the play must abort the rollout the moment a batch fails. Then run check.