backporting fix for default exponential backoff calculation (knative#…

…4116) (knative#848)

Co-authored-by: Travis Minke <travis.minke@sap.com>

pkg/kncloudevents/message_sender.go

@@ -165,7 +165,7 @@ func RetryConfigFromDeliverySpec(spec duckv1.DeliverySpec) (RetryConfig, error)
 		switch *spec.BackoffPolicy {
 		case duckv1.BackoffPolicyExponential:
 			retryConfig.Backoff = func(attemptNum int, resp *nethttp.Response) time.Duration {
-				return time.Duration(math.Pow(float64(delayDuration*2), float64(attemptNum)))
+				return delayDuration * time.Duration(math.Exp2(float64(attemptNum)))
 			}
 		case duckv1.BackoffPolicyLinear:
 			retryConfig.Backoff = func(attemptNum int, resp *nethttp.Response) time.Duration {

pkg/kncloudevents/message_sender_test.go

@@ -0,0 +1,122 @@
+/*
+Copyright 2020 The Knative Authors
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package kncloudevents
+
+import (
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+	duckv1 "knative.dev/eventing/pkg/apis/duck/v1"
+)
+
+// Test The RetryConfigFromDeliverySpec() Functionality
+func TestRetryConfigFromDeliverySpec(t *testing.T) {
+
+	// Define The TestCase Structure
+	type TestCase struct {
+		name                     string
+		retry                    int32
+		backoffPolicy            duckv1.BackoffPolicyType
+		backoffDelay             string
+		expectedBackoffDurations []time.Duration
+		wantErr                  bool
+	}
+
+	// Create The TestCases
+	testcases := []TestCase{
+		{
+			name:          "Successful Linear Backoff 2500ms",
+			retry:         int32(5),
+			backoffPolicy: duckv1.BackoffPolicyLinear,
+			backoffDelay:  "PT2.5S",
+			expectedBackoffDurations: []time.Duration{
+				2500 * time.Millisecond,
+				2500 * time.Millisecond,
+				2500 * time.Millisecond,
+				2500 * time.Millisecond,
+				2500 * time.Millisecond,
+			},
+			wantErr: false,
+		},
+		{
+			name:          "Successful Exponential Backoff 1500ms",
+			retry:         int32(5),
+			backoffPolicy: duckv1.BackoffPolicyExponential,
+			backoffDelay:  "PT1.5S",
+			expectedBackoffDurations: []time.Duration{
+				3 * time.Second,
+				6 * time.Second,
+				12 * time.Second,
+				24 * time.Second,
+				48 * time.Second,
+			},
+			wantErr: false,
+		},
+		{
+			name:          "Successful Exponential Backoff 500ms",
+			retry:         int32(5),
+			backoffPolicy: duckv1.BackoffPolicyExponential,
+			backoffDelay:  "PT0.5S",
+			expectedBackoffDurations: []time.Duration{
+				1 * time.Second,
+				2 * time.Second,
+				4 * time.Second,
+				8 * time.Second,
+				16 * time.Second,
+			},
+			wantErr: false,
+		},
+		{
+			name:          "Invalid Backoff Delay",
+			retry:         int32(5),
+			backoffPolicy: duckv1.BackoffPolicyLinear,
+			backoffDelay:  "FOO",
+			wantErr:       true,
+		},
+	}
+
+	// Loop Over The TestCases
+	for _, testcase := range testcases {
+
+		// Execute The TestCase
+		t.Run(testcase.name, func(t *testing.T) {
+
+			// Create The DeliverySpec To Test
+			deliverySpec := duckv1.DeliverySpec{
+				DeadLetterSink: nil,
+				Retry:          &testcase.retry,
+				BackoffPolicy:  &testcase.backoffPolicy,
+				BackoffDelay:   &testcase.backoffDelay,
+			}
+
+			// Create The RetryConfig From The DeliverySpec
+			retryConfig, err := RetryConfigFromDeliverySpec(deliverySpec)
+			assert.Equal(t, testcase.wantErr, err != nil)
+
+			// If Successful Then Validate The RetryConfig (Max & Backoff Calculations)
+			if err == nil {
+				assert.Equal(t, int(testcase.retry), retryConfig.RetryMax)
+				for i := 1; i < int(testcase.retry); i++ {
+					expectedBackoffDuration := testcase.expectedBackoffDurations[i-1]
+					actualBackoffDuration := retryConfig.Backoff(i, nil)
+					assert.Equal(t, expectedBackoffDuration, actualBackoffDuration)
+				}
+			}
+		})
+	}
+}