How can I migrate a live production kubernetes cluster to another cluster while minimizing downtime?

Question

I would like to migrate an application from one GKE cluster to another, and I'm wondering how to accomplish this while avoiding any downtime for this process.

The application is an HTTP web backend.

Usually how I'd usually handle this in a non GCP/K8S context is have a load balancer in front of the application, setup a new web backend and then just update the appropriate IP address in the load balancer to point from the old IP to the new IP. This would essentially have 0 downtime while also allowing for a seemless rollback if anything goes wrong.

I do not see why this should not work for this context as well however I'm not 100% sure. And if there is a more robust or alternative way to do this (GCP/GKE friendly way), I'd like to investigate that.

So to summarize my question, does GCP/GKE support this type of migration functionality? If not, is there any implications I need to be aware of with my usual load balancer approach mentioned above?

---

The reason for migrating is the current k8s cluster is running quite an old version (1.18) and if doing an GKE version upgrade to something more recent like 1.22, I suspect a lot of incompatibilities as well risk.

Answer 1

I see 2 approaches:

1. In the new cluster get a new IP address and update the DNS record to point to the new load balancer
2. See if you can switch to Multi-cluster gateways, however that would probably require you to use approach 1 to switch to multi-cluster gateways as well: https://cloud.google.com/kubernetes-engine/docs/how-to/deploying-multi-cluster-gateways