Merge pull request #59293 from roycaihw/openapi_endpoint

Automatic merge from submit-queue (batch tested with PRs 60011, 59256, 59293, 60328, 60367). If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.

Serve OpenAPI spec with single /openapi/v2 endpoint

**What this PR does / why we need it**:
We are deprecating format-separated endpoints (`/swagger.json`, `/swagger-2.0.0.json`, `/swagger-2.0.0.pb-v1`, `/swagger-2.0.0.pb-v1.gz`) for OpenAPI spec, and switching to a single `/openapi/v2` endpoint in Kubernetes 1.10. The design doc and deprecation process are tracked at: https://docs.google.com/document/d/19lEqE9lc4yHJ3WJAJxS_G7TcORIJXGHyq3wpwcH28nU

Requested format is specified by setting HTTP headers

header | possible values
-- | --
Accept | `application/json`, `application/com.github.proto-openapi.spec.v2@v1.0+protobuf`
Accept-Encoding | `gzip`

This PR changes dynamic_client (and kubectl as a result) to use the new endpoint. The old endpoints will remain in 1.10 and 1.11, and get removed in 1.12.

**Which issue(s) this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close the issue(s) when PR gets merged)*:
Fixes #

**Special notes for your reviewer**:

**Release note**:

```release-note
action required: Deprecate format-separated endpoints for OpenAPI spec. Please use single `/openapi/v2` endpoint instead.
```

/sig api-machinery

Kubernetes-commit: d6153194d929ad6c036d5bbbf67a6f892e75feb5

vendor/k8s.io/client-go/tools/cache/delta_fifo.go

@@ -38,9 +38,22 @@ import (
 // TODO: consider merging keyLister with this object, tracking a list of
 //       "known" keys when Pop() is called. Have to think about how that
 //       affects error retrying.
-// TODO(lavalamp): I believe there is a possible race only when using an
-//                 external known object source that the above TODO would
-//                 fix.
+// NOTE: It is possible to misuse this and cause a race when using an
+//       external known object source.
+//       Whether there is a potential race depends on how the comsumer
+//       modifies knownObjects. In Pop(), process function is called under
+//       lock, so it is safe to update data structures in it that need to be
+//       in sync with the queue (e.g. knownObjects).
+//
+//       Example:
+//       In case of sharedIndexInformer being a consumer
+//       (https://github.com/kubernetes/kubernetes/blob/0cdd940f/staging/
+//       src/k8s.io/client-go/tools/cache/shared_informer.go#L192),
+//       there is no race as knownObjects (s.indexer) is modified safely
+//       under DeltaFIFO's lock. The only exceptions are GetStore() and
+//       GetIndexer() methods, which expose ways to modify the underlying
+//       storage. Currently these two methods are used for creating Lister
+//       and internal tests.
 //
 // Also see the comment on DeltaFIFO.
 func NewDeltaFIFO(keyFunc KeyFunc, knownObjects KeyListerGetter) *DeltaFIFO {
@@ -199,8 +212,6 @@ func (f *DeltaFIFO) Delete(obj interface{}) error {
 		if err == nil && !exists && !itemsExist {
 			// Presumably, this was deleted when a relist happened.
 			// Don't provide a second report of the same deletion.
-			// TODO(lavalamp): This may be racy-- we aren't properly locked
-			// with knownObjects.
 			return nil
 		}
 	}
@@ -485,8 +496,6 @@ func (f *DeltaFIFO) Replace(list []interface{}, resourceVersion string) error {
 	}
 
 	// Detect deletions not already in the queue.
-	// TODO(lavalamp): This may be racy-- we aren't properly locked
-	// with knownObjects. Unproven.
 	knownKeys := f.knownObjects.ListKeys()
 	queuedDeletions := 0
 	for _, k := range knownKeys {