When a Docker Major Upgrade Took Down the Reverse Proxy (Traefik): An Incident Log
An investigation and recovery log of an outage where running apt-get upgrade bumped the Docker Engine to a new major version, after which the Traefik reverse proxy could no longer talk to the Docker API, and the Drupal site behind it became unreachable. The Docker Engine had raised the minimum supported API version, while Traefik's built-in Docker client kept trying to connect with an older API.
dockertraefikdrupalreverse-proxy