Add Context() to enable per-request cancellation

pkg/client/restclient/request.go

@@ -18,6 +18,7 @@ package restclient
 
 import (
 	"bytes"
+	"context"
 	"encoding/hex"
 	"fmt"
 	"io"
@@ -105,16 +106,14 @@ type Request struct {
 	resource     string
 	resourceName string
 	subresource  string
-	selector     labels.Selector
 	timeout      time.Duration
 
 	// output
 	err  error
 	body io.Reader
 
-	// The constructed request and the response
-	req  *http.Request
-	resp *http.Response
+	// This is only used for per-request timeouts, deadlines, and cancellations.
+	ctx context.Context
 
 	backoffMgr BackoffManager
 	throttle   flowcontrol.RateLimiter
@@ -566,6 +565,13 @@ func (r *Request) Body(obj interface{}) *Request {
 	return r
 }
 
+// Context adds a context to the request. Contexts are only used for
+// timeouts, deadlines, and cancellations.
+func (r *Request) Context(ctx context.Context) *Request {
+	r.ctx = ctx
+	return r
+}
+
 // URL returns the current working URL.
 func (r *Request) URL() *url.URL {
 	p := r.pathPrefix
@@ -651,6 +657,9 @@ func (r *Request) Watch() (watch.Interface, error) {
 	if err != nil {
 		return nil, err
 	}
+	if r.ctx != nil {
+		req = req.WithContext(r.ctx)
+	}
 	req.Header = r.headers
 	client := r.client
 	if client == nil {
@@ -720,6 +729,9 @@ func (r *Request) Stream() (io.ReadCloser, error) {
 	if err != nil {
 		return nil, err
 	}
+	if r.ctx != nil {
+		req = req.WithContext(r.ctx)
+	}
 	req.Header = r.headers
 	client := r.client
 	if client == nil {
@@ -794,6 +806,9 @@ func (r *Request) request(fn func(*http.Request, *http.Response)) error {
 		if err != nil {
 			return err
 		}
+		if r.ctx != nil {
+			req = req.WithContext(r.ctx)
+		}
 		req.Header = r.headers
 
 		r.backoffMgr.Sleep(r.backoffMgr.CalculateBackoff(r.URL()))

pkg/client/restclient/request_test.go

@@ -18,6 +18,7 @@ package restclient
 
 import (
 	"bytes"
+	"context"
 	"errors"
 	"fmt"
 	"io"
@@ -1621,3 +1622,32 @@ func testRESTClient(t testing.TB, srv *httptest.Server) *RESTClient {
 	}
 	return client
 }
+
+func TestDoContext(t *testing.T) {
+	receivedCh := make(chan struct{})
+	block := make(chan struct{})
+	testServer := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
+		close(receivedCh)
+		<-block
+		w.WriteHeader(http.StatusOK)
+	}))
+	defer testServer.Close()
+	defer close(block)
+
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	go func() {
+		<-receivedCh
+		cancel()
+	}()
+
+	c := testRESTClient(t, testServer)
+	_, err := c.Verb("GET").
+		Context(ctx).
+		Prefix("foo").
+		DoRaw()
+	if err == nil {
+		t.Fatal("Expected context cancellation error")
+	}
+}