Currently, kubeadm would refuse to perfom an upgrade (or even planing for one)
if it detects a user supplied unsupported component config version. Hence,
users are required to manually upgrade their component configs and store them
in the config maps prior to executing `kubeadm upgrade plan` or
`kubeadm upgrade apply`.
This change introduces the ability to use the `--config` option of the
`kubeadm upgrade plan` and `kubeadm upgrade apply` commands to supply a YAML
file containing component configs to be used in place of the existing ones in
the cluster upon upgrade.
The old behavior where `--config` is used to reconfigure a cluster is still
supported. kubeadm automatically detects which behavior to use based on the
presence (or absense) of kubeadm config types (API group
`kubeadm.kubernetes.io`).
Signed-off-by: Rostislav M. Georgiev <rostislavg@vmware.com>
Until now, users were always asked to manually convert a component config to a
version supported by kubeadm, if kubeadm is not supporting its version.
This is true even for configs generated with older kubeadm versions, hence
getting users to make manual conversions on kubeadm generated configs.
This is not appropriate and user friendly, although, it tends to be the most
common case. Hence, we sign kubeadm generated component configs stored in
config maps with a SHA256 checksum. If a configs is loaded by kubeadm from a
config map and has a valid signature it's considered "kubeadm generated" and if
a version migration is required, this config is automatically discarded and a
new one is generated.
If there is no checksum or the checksum is not matching, the config is
considered as "user supplied" and, if a version migration is required, kubeadm
will bail out with an error, requiring manual config migration (as it's today).
The behavior when supplying component configs on the kubeadm command line
does not change. Kubeadm would still bail out with an error requiring migration
if it can recognize their groups but not versions.
Signed-off-by: Rostislav M. Georgiev <rostislavg@vmware.com>
kubeadm's current implementation of component config support is "kind" centric.
This has its downsides. Namely:
- Kind names and numbers can change between config versions.
Newer kinds can be ignored. Therefore, detection of a version change is
considerably harder.
- A component config can have only one kind that is managed by kubeadm.
Thus a more appropriate way to identify component configs is required.
Probably the best solution identified so far is a config group.
A group name is unlikely to change between versions, while the kind names and
structure can.
Tracking component configs by group name allows us to:
- Spot more easily config version changes and manage alternate versions.
- Support more than one kind in a config group/version.
- Abstract component configs by hiding their exact structure.
Hence, this change rips off the old kind based support for component configs
and replaces it with a group name based one. This also has the following
extra benefits:
- More tests were added.
- kubeadm now errors out if an unsupported version of a known component group
is used.
Signed-off-by: Rostislav M. Georgiev <rostislavg@vmware.com>
