Potential race condition when migrating ingress-nginx to traefik

[megabreit]

After reading Use ingress-nginx Resources in Traefik | Traefik Labs i tried this method with version 3.6.7 (bundled with RKE2). It is working fine so far if the ingressClassName is set to nginx. Both Ingress controllers are using the same Ingress at the same time. Now I compare this with the “official” migration documentation from Suse (sadly not available in public). They suggest a different way because there could be race conditions between the both ingress controllers trying to update the same ingress, and to avoid that, they set a different (non-empty) ingressClassName for the compatibility mode in their Helm values. In particular they set providers.kubernetesIngressNginx.ingressClass="rke2-ingress-nginx-migration". This is also working, but involves a downtime to switch over the traffic to the new loadbalancer. I like the other method better, because with it a real seamless migration would be possible. It’s just necessary to switch the ports of the existing loadbalancer service. But I can’t really judge the danger of such a configuration. In my tests I didn’t see a race condition in the logs, but this doesn’t mean that there is none, maybe I just don’t see it with the current log level? Has anybody here some insights about that?