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

discovery/discovery_client.go

@@ -36,8 +36,12 @@ import (
 	restclient "k8s.io/client-go/rest"
 )
 
-// defaultRetries is the number of times a resource discovery is repeated if an api group disappears on the fly (e.g. ThirdPartyResources).
-const defaultRetries = 2
+const (
+	// defaultRetries is the number of times a resource discovery is repeated if an api group disappears on the fly (e.g. ThirdPartyResources).
+	defaultRetries = 2
+	// protobuf mime type
+	mimePb = "application/com.github.proto-openapi.spec.v2@v1.0+protobuf"
+)
 
 // DiscoveryInterface holds the methods that discover server-supported API groups,
 // versions and resources.
@@ -329,9 +333,18 @@ func (d *DiscoveryClient) ServerVersion() (*version.Info, error) {
 
 // OpenAPISchema fetches the open api schema using a rest client and parses the proto.
 func (d *DiscoveryClient) OpenAPISchema() (*openapi_v2.Document, error) {
-	data, err := d.restClient.Get().AbsPath("/swagger-2.0.0.pb-v1").Do().Raw()
+	data, err := d.restClient.Get().AbsPath("/openapi/v2").SetHeader("Accept", mimePb).Do().Raw()
 	if err != nil {
-		return nil, err
+		if errors.IsForbidden(err) || errors.IsNotFound(err) {
+			// single endpoint not found/registered in old server, try to fetch old endpoint
+			// TODO(roycaihw): remove this in 1.11
+			data, err = d.restClient.Get().AbsPath("/swagger-2.0.0.pb-v1").Do().Raw()
+			if err != nil {
+				return nil, err
+			}
+		} else {
+			return nil, err
+		}
 	}
 	document := &openapi_v2.Document{}
 	err = proto.Unmarshal(data, document)

discovery/discovery_client_test.go

@@ -326,9 +326,14 @@ var returnedOpenAPI = openapi_v2.Document{
 	},
 }
 
-func openapiSchemaFakeServer() (*httptest.Server, error) {
+func openapiSchemaDeprecatedFakeServer() (*httptest.Server, error) {
 	var sErr error
 	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
+		// old server returns 403 on new endpoint request
+		if req.URL.Path == "/openapi/v2" {
+			w.WriteHeader(http.StatusForbidden)
+			return
+		}
 		if req.URL.Path != "/swagger-2.0.0.pb-v1" {
 			sErr = fmt.Errorf("Unexpected url %v", req.URL)
 		}
@@ -349,6 +354,33 @@ func openapiSchemaFakeServer() (*httptest.Server, error) {
 	return server, sErr
 }
 
+func openapiSchemaFakeServer() (*httptest.Server, error) {
+	var sErr error
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
+		if req.URL.Path != "/openapi/v2" {
+			sErr = fmt.Errorf("Unexpected url %v", req.URL)
+		}
+		if req.Method != "GET" {
+			sErr = fmt.Errorf("Unexpected method %v", req.Method)
+		}
+		decipherableFormat := req.Header.Get("Accept")
+		if decipherableFormat != "application/com.github.proto-openapi.spec.v2@v1.0+protobuf" {
+			sErr = fmt.Errorf("Unexpected accept mime type %v", decipherableFormat)
+		}
+
+		mime.AddExtensionType(".pb-v1", "application/com.github.googleapis.gnostic.OpenAPIv2@68f4ded+protobuf")
+
+		output, err := proto.Marshal(&returnedOpenAPI)
+		if err != nil {
+			sErr = err
+			return
+		}
+		w.WriteHeader(http.StatusOK)
+		w.Write(output)
+	}))
+	return server, sErr
+}
+
 func TestGetOpenAPISchema(t *testing.T) {
 	server, err := openapiSchemaFakeServer()
 	if err != nil {
@@ -366,6 +398,23 @@ func TestGetOpenAPISchema(t *testing.T) {
 	}
 }
 
+func TestGetOpenAPISchemaFallback(t *testing.T) {
+	server, err := openapiSchemaDeprecatedFakeServer()
+	if err != nil {
+		t.Errorf("unexpected error starting fake server: %v", err)
+	}
+	defer server.Close()
+
+	client := NewDiscoveryClientForConfigOrDie(&restclient.Config{Host: server.URL})
+	got, err := client.OpenAPISchema()
+	if err != nil {
+		t.Fatalf("unexpected error getting openapi: %v", err)
+	}
+	if e, a := returnedOpenAPI, *got; !reflect.DeepEqual(e, a) {
+		t.Errorf("expected %v, got %v", e, a)
+	}
+}
+
 func TestServerPreferredResources(t *testing.T) {
 	stable := metav1.APIResourceList{
 		GroupVersion: "v1",