Support for apply command

[jhavero]

Does this gem support applying yaml files declaratively? For example 'kubectl apply -f file.yml'

[cben]

Not currently.
You can completely replace an object with update_pod() etc.
You can patch specific parts of an object with patch_pod() etc. (currently using "strategic merge patch", want to add others, see #357).
There are several hurdles to process a yaml file with many objects — #329. The next step to make that easier is #332.

But kubectl apply has considerate client-side smarts for not trampling over "external" changes to the object — it records the last applied input in an annotation, and then does something akin to 3-way merge of "last applied" — "new to apply" — "actual".
I'm not sure it's productive to replicate this merging in kubeclient...

Any PRs welcome of course :)

I must say at this point, if what you need is exactly the functionality of apply, shelling out to kubectl is the easy path...

[rhysm]

Server Side Apply is now available as Alpha in Kubernetes 1.14.

Server Side Apply allows clients other than kubectl to perform the Apply operation, and will eventually fully replace the complicated Client Side Apply logic that only exists in kubectl. If the Server Side Apply feature is enabled, the PATCH endpoint accepts the additional application/apply-patch+yaml content type. Users of Server Side Apply can send partially specified objects to this endpoint. An applied config should always include every field that the applier has an opinion about.

I haven't had a chance to look at it yet but if you can also specify application/apply-patch+json to the PATCH endpoint then this is supported already specifying apply-patch as the strategy to patch_entity.

[cben]

• This adds a new metadata.managedFields field. Do we need anything special to support metadata fields?
  UPDATE: looking at do not crash when reverting with server-side-apply zendesk/samson#3699, maybe this is not a concern of kubeclient needs to do, just calling code has to be careful about?

• This allows a new fieldManager param to various operations, required on apply operation
  => tracked in issue support params for patch #427

[grosser]

FYI: samson now uses server-side-apply via header-hacks to do this zendesk/samson#3676

[benlangfeld]

Abstract server-side apply support is in #448. I didn't address any more generic interface.