How Different Docker Engine Versions Led to Partial Traffic Unavailability in Docker Swarm
If different Docker Engine versions are running simultaneously in a Docker Swarm cluster, this may lead not to an obvious service outage but to a more subtle scenario: partial traffic degradation on individual nodes. In this case, the issue appeared on one of the manager nodes, Traefik started reporting an unavailable status (health=0) for the router-app service, and the cause, according to the working hypothesis, was related to differences in iptables rules and overlay networking between Docker
