Order of Volumes and VolumeMounts in the pod objects created by
kubeadm is undefined as they're represended as maps in the
controlPlaneHostPathMounts struct.
This influences 'kubeadm upgrade' logic in a way that even when
manifest of the component is not changed kubeadm tries to upgrade
it because most of the time current and new pods are not equal
due to the different order of Volumes and VolumeMounts.
For example 'kubeadm apply diff' almost always shows difference
in Volumes and VolumeMounts because of this:
volumeMounts:
+ - mountPath: /etc/kubernetes/pki
+ name: k8s-certs
+ readOnly: true
- mountPath: /etc/ssl/certs
name: ca-certs
+ readOnly: true
+ - mountPath: /etc/pki
+ name: etc-pki
+ readOnly: true
+ - mountPath: /usr/share/ca-certificates
+ name: usr-share-ca-certificates
readOnly: true
- mountPath: /etc/ca-certificates
name: etc-ca-certificates
readOnly: true
- - mountPath: /etc/pki
- name: etc-pki
- readOnly: true
- - mountPath: /etc/kubernetes/pki
- name: k8s-certs
- readOnly: true
- - mountPath: /usr/share/ca-certificates
- name: usr-share-ca-certificates
- readOnly: true
Sorting Volumes and VolumeMounts should fix this issue and help
to avoid unnecessary upgrades.
When doing upgrades kubeadm generates new manifest and
waits until kubelet restarts correspondent pod.
However, kubelet won't restart pod if there are no changes
in the manifest. That makes kubeadm stuck waiting for
restarted pod.
Skipping upgrade if new component manifest is the same as
current manifest should solve this.
Fixes: kubernetes/kubeadm#1054
