client-go/rest: backoff with context support

The BackoffManager interface sleeps without considering the caller's context,
i.e. cancellation is not supported. This alone is reason enough to deprecate it
and to replace it with an interface that supports a context parameter.

The other reason is that contextual logging needs that parameter.

Kubernetes-commit: b15a1943d51adfb8c5e0185d58d25e038c3d6ade

rest/urlbackoff_test.go

@@ -17,10 +17,14 @@ limitations under the License.
 package rest
 
 import (
+	"context"
+	"errors"
 	"net/url"
 	"testing"
 	"time"
 
+	"github.com/stretchr/testify/assert"
+
 	"k8s.io/client-go/util/flowcontrol"
 )
 
@@ -77,3 +81,38 @@ func TestURLBackoffFunctionality(t *testing.T) {
 		t.Errorf("The final return code %v should have resulted in a backoff ! ", returnCodes[7])
 	}
 }
+
+func TestBackoffManagerNopContext(t *testing.T) {
+	mock := NewMockBackoffManager(t)
+
+	sleepDuration := 42 * time.Second
+	mock.On("Sleep", sleepDuration).Return()
+	url := &url.URL{}
+	mock.On("CalculateBackoff", url).Return(time.Second)
+	err := errors.New("fake error")
+	responseCode := 404
+	mock.On("UpdateBackoff", url, err, responseCode).Return()
+
+	ctx := context.Background()
+	wrapper := backoffManagerNopContext{BackoffManager: mock}
+	wrapper.SleepWithContext(ctx, sleepDuration)
+	wrapper.CalculateBackoffWithContext(ctx, url)
+	wrapper.UpdateBackoffWithContext(ctx, url, err, responseCode)
+}
+
+func TestNoBackoff(t *testing.T) {
+	var backoff NoBackoff
+	assert.Equal(t, 0*time.Second, backoff.CalculateBackoff(nil))
+	assert.Equal(t, 0*time.Second, backoff.CalculateBackoffWithContext(context.Background(), nil))
+
+	start := time.Now()
+	backoff.Sleep(0 * time.Second)
+	assert.WithinDuration(t, start, time.Now(), time.Minute /* pretty generous, but we don't want to flake */, time.Since(start), "backoff.Sleep")
+
+	// Cancel right away to prevent sleeping.
+	ctx, cancel := context.WithCancel(context.Background())
+	cancel()
+	start = time.Now()
+	backoff.SleepWithContext(ctx, 10*time.Minute)
+	assert.WithinDuration(t, start, time.Now(), time.Minute /* pretty generous, but we don't want to flake */, time.Since(start), "backoff.SleepWithContext")
+}