I'd like to upgrade my GKE cluster to enable VPC-Native networking.
For that, I'm in need of creating new GKE Cluster. While I more or less know how to migrate my own deployments there and have a general strategy to not make a disruption, one thing that I'm unable to figure out is how to migrate the traffic from one cluster to another.
Let's label the clusters as OLD-GKE one I want to migrate off of, and NEW-GKE to which I want to migrate onto.
I've a HTTP(s) reverse proxy deployment in the OLD-GKE that handles the traffic and distributes it further to respective services inside the OLD-GKE. That reverse proxy has K8s Service of type LoadBalancer associated with it, and in Google Cloud, IP associated with that LB is marked as static.
I'd like to replicate the setup in NEW-GKE, but one problem I'm facing with is that NEW-GKE will not be able to create LB Service with that same IP until that IP is released from OLD-GKE service.
Removing service in OLD-GKE with that IP will cause a downtime between that removal and until NEW-GKE service controller picks up the IP and starts accepting traffic.
I'm aware of multi-cluster Services, however at most there will be always a single cluster and I just want to be able to handle the transition without downtime (and that might happen every half a year or so, just for testing disaster recovery scenarios for example).
I'm trying to come up with a solution to migrate Static IP to a new GKE LB Service without downtime, what are available solutions to that problem?
Best if it could be done using managed services in GCP so I can manage it through terraform and make that independent of what it is directed at (be it GKE services, or VM, or anything in the future).
