Use request Context for admission Webhook handlers

Author: Steve Harris

pkg/webhook/admission/http.go

@@ -17,7 +17,6 @@ limitations under the License.
 package admission
 
 import (
-	"context"
 	"encoding/json"
 	"errors"
 	"fmt"
@@ -84,7 +83,7 @@ func (wh *Webhook) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	}
 
 	// TODO: add panic-recovery for Handle
-	reviewResponse = wh.Handle(context.Background(), req)
+	reviewResponse = wh.Handle(r.Context(), req)
 	wh.writeResponse(w, reviewResponse)
 }
 

pkg/webhook/admission/http_test.go

@@ -19,6 +19,7 @@ package admission
 import (
 	"bytes"
 	"context"
+	"fmt"
 	"io"
 	"net/http"
 	"net/http/httptest"
@@ -94,6 +95,32 @@ var _ = Describe("Admission Webhooks", func() {
 			webhook.ServeHTTP(respRecorder, req)
 			Expect(respRecorder.Body.Bytes()).To(Equal(expected))
 		})
+
+		It("should present the Context from the HTTP request, if any", func() {
+			req := &http.Request{
+				Header: http.Header{"Content-Type": []string{"application/json"}},
+				Body:   nopCloser{Reader: bytes.NewBufferString(`{"request":{}}`)},
+			}
+			type ctxkey int
+			const key ctxkey = 1
+			const value = "from-ctx"
+			webhook := &Webhook{
+				Handler: &fakeHandler{
+					fn: func(ctx context.Context, req Request) Response {
+						<-ctx.Done()
+						return Allowed(ctx.Value(key).(string))
+					},
+				},
+			}
+
+			expected := []byte(fmt.Sprintf(`{"response":{"uid":"","allowed":true,"status":{"metadata":{},"reason":%q,"code":200}}}
+`, value))
+
+			ctx, cancel := context.WithCancel(context.WithValue(context.Background(), key, value))
+			cancel()
+			webhook.ServeHTTP(respRecorder, req.WithContext(ctx))
+			Expect(respRecorder.Body.Bytes()).To(Equal(expected))
+		})
 	})
 })
 

pkg/webhook/admission/webhook.go

@@ -92,6 +92,10 @@ func (r *Response) Complete(req Request) error {
 
 // Handler can handle an AdmissionRequest.
 type Handler interface {
+	// Handle yields a response to an AdmissionRequest.
+	//
+	// The supplied context is extracted from the received http.Request, if any, allowing wrapping
+	// http.Handlers to inject values into and control cancelation of downstream request processing.
 	Handle(context.Context, Request) Response
 }