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Refactor to simplify the hard-traveled path of the KubeletConfiguration object
### There are two main goals of this PR:
- Make `NewMainKubelet` take `KubeletConfiguration` and `KubeletDeps` as its only arguments.
- Finally eliminate the legacy `KubeletConfig` type.
### Why am I doing this?
Long story short, I started adding an endpoint to the Kubelet to display the *current* config that the Kubelet was running with, and I realized a few things:
- There were so many transformations to the configuration, in so many different places, before it was used that I wasn't confident the values initially passed in on the `KubeletConfiguration` would be the correct values to report by the time someone used the endpoint to check on them.
- Trying to reconstruct a `KubeletConfiguration` object from a mix of the `Kubelet` object and the legacy `KubeletConfig` object would just add to the mess (not to mention maintenance burden), and it would be much easier if we passed the `KubeletConfiguration` all the way down to where we construct the `Kubelet` object, and then just store a reference to the `KubeletConfiguration` object on the `Kubelet` for later retrieval.
- My hope is that by eliminating unnecessary internal transformations to the config information, and by consolidating the remaining ones in a single place (`NewMainKubelet`), we can have a much clearer understanding of what happens to the config before it makes it to the `Kubelet` object, and also a better ability to report up-to-date information on the status of the Kubelet.
So I started cleaning things up :-).
### Discussion points
It was relatively simple to get `NewMainKubelet` to just take the legacy `KubeletConfig` as its only argument, because most of its arguments were just passing through `KubeletConfig` fields or passing information that was generated solely from `KubeletConfig` fields.
Completely eliminating the legacy `KubeletConfig` type has been more difficult, because the fields of the `KubeletConfiguration` do not have a one-to-one relationship with the fields of the `KubeletConfig`. While I was able to eliminate many of the `KubeletConfig` fields, I'm starting to get into the nontrivial stuff and I'd like to get a discussion started on what should happen with the remaining fields (pending cherry-picking notwithstanding).
On my `kconf-refactor` branch, the legacy `KubeletConfig` object is down to the following 27 fields (from the initial 93). I'd really appreciate any guidance people have on what should happen with these fields.
```
type KubeletConfig struct {
Auth server.AuthInterface
AutoDetectCloudProvider bool
Builder KubeletBuilder
CAdvisorInterface cadvisor.Interface
Cloud cloudprovider.Interface
ContainerManager cm.ContainerManager
DockerClient dockertools.DockerInterface
EventClient *clientset.Clientset
Hostname string
HostNetworkSources []string
HostPIDSources []string
HostIPCSources []string
KubeClient *clientset.Clientset
Mounter mount.Interface
NetworkPlugins []network.NetworkPlugin
NodeName string
OOMAdjuster *oom.OOMAdjuster
OSInterface kubecontainer.OSInterface
PodConfig *config.PodConfig
Recorder record.EventRecorder
Reservation kubetypes.Reservation
TLSOptions *server.TLSOptions
Writer kubeio.Writer
VolumePlugins []volume.VolumePlugin
EvictionConfig eviction.Config
ContainerRuntimeOptions []kubecontainer.Option
Options []Option
}
```
The patterns I've seen so far with respect to eliminating `KubeletConfig` fields may be of some help:
- Some fields could just be eliminated, because they were either the same on `KubeletConfiguration` or just a typecast away from being the same.
- Some fields from `KubeletConfiguration` just ended up in substructures of `KubeletConfig`; it was easy to just remove those substructure fields from `KubeletConfig` and construct them using local vars in `NewMainKubelet` instead.
- Some fields, e.g. `Runonce`, were able to move into the `KubeletConfiguration`.
**P.S.** Part of the way I'm making the transition is by adding an extra `KubeletConfiguration` argument to functions that originally took a `KubeletConfig`, and field-by-field, switching those functions over to using information from the `KubeletConfiguration`. Once the `KubeletConfig` is gone, I'll remove the `KubeletConfig` argument, and the transition will be complete.
**Final note:**
Please try to keep in mind that this is not a general Kubelet cleanup effort, it is just me cleaning things up that are directly in the path of what I'm trying to do. Let's keep this focused on cleanup related to the path that config takes on it's way to the Kubelet.
**Release note**:
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```
Removed Flags
- Removes the --auth-path flag. This has been deprecated in favor of --kubeconfig for two releases.
```
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