OpenShift 4 Migration: A sample path
The Problem
Moving stuff between Kubernetes clusters can be a pain in the butt. You have to do this when:
- Migrating between container platforms, such as EKS -> AKS
- Upgrading clusters when you want to upgrade in parallel (move everything from old to new) as opposed to upgrading in-place (update one cluster from old to new). This would be something like what we’ll talk about in a minute, going from OpenShift 3.x to OpenShift 4.x
- Moving work/applications between clusters, e.g. two clusters in different datacenters
Migrating work between clusters requires some thought and planning, and good solid processes. Specifically, the migration from OpenShift 3.x to OpenShift 4.x requires a parallel upgrade, because there is no in-place upgrade available for all of the new goodies in RHEL CoreOS (the underlying infrastructure of the cluster). OpenShift 4.2 released recently, so we thought it would be good timing to put our migration thoughts down here. However, the advice below is generally good for any Kubernetes cluster parallel upgrade or other migration.
So you’re a Java/C++/web developer and you’ve heard about all of these “cloud native” technologies, and containers, and you’re wondering “excuse me, what is a Kubernetes please, and why do I care?”