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Upgrading Kubernetes in Kubespray

Description

Kubespray handles upgrades the same way it handles initial deployment. That is to say that each component is laid down in a fixed order. You should be able to upgrade from Kubespray tag 2.0 up to the current master without difficulty. You can also individually control versions of components by explicitly defining their versions. Here are all version vars for each component:

  • docker_version
  • kube_version
  • etcd_version
  • calico_version
  • calico_cni_version
  • weave_version
  • flannel_version
  • kubedns_version

Unsafe upgrade example

If you wanted to upgrade just kube_version from v1.4.3 to v1.4.6, you could deploy the following way:

ansible-playbook cluster.yml -i inventory/inventory.cfg -e kube_version=v1.4.3

And then repeat with v1.4.6 as kube_version:

ansible-playbook cluster.yml -i inventory/inventory.cfg -e kube_version=v1.4.6

Graceful upgrade

Kubespray also supports cordon, drain and uncordoning of nodes when performing a cluster upgrade. There is a separate playbook used for this purpose. It is important to note that upgrade-cluster.yml can only be used for upgrading an existing cluster. That means there must be at least 1 kube-master already deployed.

git fetch origin
git checkout origin/master
ansible-playbook upgrade-cluster.yml -b -i inventory/inventory.cfg -e kube_version=v1.6.0

After a successul upgrade, the Server Version should be updated:

$ kubectl version
Client Version: version.Info{Major:"1", Minor:"6", GitVersion:"v1.6.0", GitCommit:"fff5156092b56e6bd60fff75aad4dc9de6b6ef37", GitTreeState:"clean", BuildDate:"2017-03-28T19:15:41Z", GoVersion:"go1.8", Compiler:"gc", Platform:"darwin/amd64"}
Server Version: version.Info{Major:"1", Minor:"6", GitVersion:"v1.6.0+coreos.0", GitCommit:"8031716957d697332f9234ddf85febb07ac6c3e3", GitTreeState:"clean", BuildDate:"2017-03-29T04:33:09Z", GoVersion:"go1.7.5", Compiler:"gc", Platform:"linux/amd64"}

Upgrade order

As mentioned above, components are upgraded in the order in which they were installed in the Ansible playbook. The order of component installation is as follows:

  • Docker
  • etcd
  • kubelet and kube-proxy
  • network_plugin (such as Calico or Weave)
  • kube-apiserver, kube-scheduler, and kube-controller-manager
  • Add-ons (such as KubeDNS)

Upgrade considerations

Kubespray supports rotating certificates used for etcd and Kubernetes components, but some manual steps may be required. If you have a pod that requires use of a service token and is deployed in a namespace other than kube-system, you will need to manually delete the affected pods after rotating certificates. This is because all service account tokens are dependent on the apiserver token that is used to generate them. When the certificate rotates, all service account tokens must be rotated as well. During the kubernetes-apps/rotate_tokens role, only pods in kube-system are destroyed and recreated. All other invalidated service account tokens are cleaned up automatically, but other pods are not deleted out of an abundance of caution for impact to user deployed pods.