The retry labels (Traefik retry middleware, Caddy lb_try_duration)
changed the labels of every application. On the first rolling update
after a settings save, the old and the new container defined the same
Traefik router differently, so Traefik dropped the route and returned
503 until the old container stopped.
Remove the retry labels from this release. The rolling update drain
wait stays.
Traefik and Caddy routes of applications now retry a failed connection
on another container, and the rolling update waits a configurable drain
time (default 5 seconds) after the new container is healthy before it
stops the old containers. The wait is skipped when no old container runs
or when the proxy labels changed, because the proxy drops a route that
two containers define differently.
Fixes#8627
Andras Bacsai