What is the recommended way to upgrade a kubernetes cluster as new versions are released?
I heard here it may be https://github.com/kubernetes/kubernetes/blob/master/cluster/kube-push.sh. If that is the case how does kube-push.sh relate to https://github.com/GoogleCloudPlatform/kubernetes/blob/master/cluster/gce/upgrade.sh?
I've also heard here that we should instead create a new cluster, copy/move the pods, replication controllers, and services from the first cluster to the new one and then turn off the first cluster.
I'm running my cluster on aws if that is relevant.
The second script you reference (gce/upgrade.sh) only works if your cluster is running on GCE. There isn't (yet) an equivalent script for AWS, but you could look at the script and follow the steps (or write them into a script) to get the same behavior.
The main different between upgrade.sh and kube-push.sh is that the former does a replacement upgrade (remove a node, create a new node to replace it) whereas the later does an "in place" upgrade.
Removing and replacing the master node only works if the persistent data (etcd database, server certificates, authorized bearer tokens, etc) reside on a persistent disk separate from the boot disk of the master (this is how it is configured by default in GCE). Remove and replacing nodes should be fine on AWS (but keep in mind that any pods not under a replication controller won't be restarted).
Doing an in-place upgrade doesn't require any special configuration, but that code path isn't as thoroughly tested as the remove and replace option.
You shouldn't need to entirely replace your cluster when upgrading to a new version, unless you are using pre-release versions (e.g. alpha or beta releases) which can sometimes have breaking changes between them.