Compose readiness and partial rollback boundaries

A running container may still lack a database connection, required tables, or an internal dependency. Liveness says the process is alive; readiness says it can receive user traffic.

Warragon PROD keeps the public entry at Caddy and binds app, database, Kafka, and Prometheus ports to loopback or the internal network. Java Actuator and Python /metrics are internal scrape paths, while Caddy blocks public management routes. Prometheus starts only in the optional observability profile.

Admin writes the Codingstairs upload host path and the public app mounts that same path read-only. A mismatch would make an upload appear successful while the public page cannot read it.

On failure, replace and roll back only target images rather than stopping the whole stack. Preserve logs and readiness results so the operator can judge impact and recovery.

Related course: Compose, readiness, reverse proxy, and rollback