[release-1.9] Fixes issue where a CE response is truncated (#6784)

```release-note
🐛 Fixes an issue where a Cloud Event in a response from a sink was truncated to 1024 bytes
```

pkg/channel/message_dispatcher.go

@@ -239,30 +239,28 @@ func (d *MessageDispatcherImpl) executeRequest(ctx context.Context,
 	}
 	execInfo.Time = dispatchTime
 
-	body := make([]byte, attributes.KnativeErrorDataExtensionMaxLength)
+	body := new(bytes.Buffer)
+	_, readErr := body.ReadFrom(response.Body)
 
 	if isFailure(response.StatusCode) {
 		// Read response body into execInfo for failures
-		readLen, err := response.Body.Read(body)
-		if err != nil && err != io.EOF {
-			d.logger.Error("failed to read response body into DispatchExecutionInfo", zap.Error(err))
+		if readErr != nil && readErr != io.EOF {
+			d.logger.Error("failed to read response body", zap.Error(err))
 			execInfo.ResponseBody = []byte(fmt.Sprintf("dispatch error: %s", err.Error()))
 		} else {
-			execInfo.ResponseBody = body[:readLen]
+			execInfo.ResponseBody = body.Bytes()
 		}
 		_ = response.Body.Close()
 		// Reject non-successful responses.
 		return ctx, nil, nil, &execInfo, fmt.Errorf("unexpected HTTP response, expected 2xx, got %d", response.StatusCode)
 	}
 
 	var responseMessageBody []byte
-	// Read response body into responseMessage for message accepted
-	readLen, err := response.Body.Read(body)
-	if err != nil && err != io.EOF {
-		d.logger.Error("failed to read response body into cloudevents' Message", zap.Error(err))
+	if readErr != nil && readErr != io.EOF {
+		d.logger.Error("failed to read response body", zap.Error(err))
 		responseMessageBody = []byte(fmt.Sprintf("Failed to read response body: %s", err.Error()))
 	} else {
-		responseMessageBody = body[:readLen]
+		responseMessageBody = body.Bytes()
 	}
 	responseMessage := http.NewMessage(response.Header, io.NopCloser(bytes.NewReader(responseMessageBody)))
 

pkg/channel/message_dispatcher_test.go

@@ -723,6 +723,69 @@ func TestDispatchMessage(t *testing.T) {
 			},
 			lastReceiver: "deadLetter",
 		},
+		"no restriction on message response size": {
+			sendToDestination: true,
+			sendToReply:       true,
+			hasDeadLetterSink: false,
+			header: map[string][]string{
+				// do-not-forward should not get forwarded.
+				"do-not-forward": {"header"},
+				"x-request-id":   {"id123"},
+				"knative-1":      {"knative-1-value"},
+				"knative-2":      {"knative-2-value"},
+			},
+			body: "destination",
+			eventExtensions: map[string]string{
+				"abc": `"ce-abc-value"`,
+			},
+			expectedDestRequest: &requestValidation{
+				Headers: map[string][]string{
+					"x-request-id":   {"id123"},
+					"knative-1":      {"knative-1-value"},
+					"knative-2":      {"knative-2-value"},
+					"prefer":         {"reply"},
+					"traceparent":    {"ignored-value-header"},
+					"ce-abc":         {`"ce-abc-value"`},
+					"ce-id":          {"ignored-value-header"},
+					"ce-time":        {"2002-10-02T15:00:00Z"},
+					"ce-source":      {testCeSource},
+					"ce-type":        {testCeType},
+					"ce-specversion": {cloudevents.VersionV1},
+				},
+				Body: `"destination"`,
+			},
+			expectedReplyRequest: &requestValidation{
+				Headers: map[string][]string{
+					"x-request-id":   {"id123"},
+					"knative-1":      {"knative-1-value"},
+					"traceparent":    {"ignored-value-header"},
+					"ce-abc":         {`"ce-abc-value"`},
+					"ce-id":          {"ignored-value-header"},
+					"ce-time":        {"2002-10-02T15:00:00Z"},
+					"ce-source":      {testCeSource},
+					"ce-type":        {testCeType},
+					"ce-specversion": {cloudevents.VersionV1},
+				},
+				Body: strings.Repeat("a", 2000),
+			},
+			fakeResponse: &http.Response{
+				StatusCode: http.StatusAccepted,
+				Header: map[string][]string{
+					"do-not-passthrough": {"no"},
+					"x-request-id":       {"id123"},
+					"knative-1":          {"knative-1-value"},
+					"ce-abc":             {`"ce-abc-value"`},
+					"ce-id":              {"ignored-value-header"},
+					"ce-time":            {"2002-10-02T15:00:00Z"},
+					"ce-source":          {testCeSource},
+					"ce-type":            {testCeType},
+					"ce-specversion":     {cloudevents.VersionV1},
+				},
+				Body: io.NopCloser(bytes.NewBufferString(strings.Repeat("a", 2000))),
+			},
+
+			lastReceiver: "reply",
+		},
 	}
 	for n, tc := range testCases {
 		t.Run(n, func(t *testing.T) {

test/rekt/broker_test.go

@@ -202,3 +202,18 @@ func TestBrokerDeliverLongMessage(t *testing.T) {
 
 	env.TestSet(ctx, t, broker.BrokerDeliverLongMessage())
 }
+
+func TestBrokerDeliverLongResponseMessage(t *testing.T) {
+	t.Parallel()
+
+	ctx, env := global.Environment(
+		knative.WithKnativeNamespace(system.Namespace()),
+		knative.WithLoggingConfig,
+		knative.WithTracingConfig,
+		k8s.WithEventListener,
+		environment.Managed(t),
+		environment.WithPollTimings(5*time.Second, 4*time.Minute),
+	)
+
+	env.TestSet(ctx, t, broker.BrokerDeliverLongResponseMessage())
+}

test/rekt/features/broker/feature.go

@@ -617,3 +617,96 @@ func brokerSubscriberLongMessage() *feature.Feature {
 	)
 	return f
 }
+
+/*
+Following test sends an event to the first sink, Sink1, which will send a long response destined to Sink2.
+The test will assert that the long response is received by Sink2
+
+EventSource ---> Broker ---> Trigger1 ---> Sink1(Transformation) ---> Trigger2 --> Sink2
+*/
+
+func BrokerDeliverLongResponseMessage() *feature.FeatureSet {
+	fs := &feature.FeatureSet{
+		Name: "Knative Broker - Long Response Message",
+
+		Features: []*feature.Feature{
+			brokerSubscriberLongResponseMessage(),
+		},
+	}
+	return fs
+}
+
+func brokerSubscriberLongResponseMessage() *feature.Feature {
+	f := feature.NewFeatureNamed("Broker, chain of Triggers, long response message from first subscriber")
+
+	source := feature.MakeRandomK8sName("source")
+	sink1 := feature.MakeRandomK8sName("sink1")
+	sink2 := feature.MakeRandomK8sName("sink2")
+	trigger1 := feature.MakeRandomK8sName("trigger1")
+	trigger2 := feature.MakeRandomK8sName("trigger2")
+
+	eventSource1 := "source1"
+	eventSource2 := "source2"
+	eventType1 := "type1"
+	eventType2 := "type2"
+	eventBody := `{"msg":"eventBody"}`
+	transformedEventBody := `{"msg":"` + strings.Repeat("X", 36000) + `"}`
+	event := cloudevents.NewEvent()
+	event.SetID(uuid.New().String())
+	event.SetType(eventType1)
+	event.SetSource(eventSource1)
+	event.SetData(cloudevents.TextPlain, []byte(eventBody))
+
+	//Install the broker
+	brokerName := feature.MakeRandomK8sName("broker")
+	f.Setup("install broker", broker.Install(brokerName, broker.WithEnvConfig()...))
+	f.Requirement("broker is ready", broker.IsReady(brokerName))
+	f.Requirement("broker is addressable", broker.IsAddressable(brokerName))
+
+	// Sink1 will transform the event so it can be filtered by Trigger2
+	f.Setup("install sink1", eventshub.Install(
+		sink1,
+		eventshub.ReplyWithTransformedEvent(eventType2, eventSource2, transformedEventBody),
+		eventshub.StartReceiver,
+	))
+
+	f.Setup("install sink2", eventshub.Install(sink2, eventshub.StartReceiver))
+
+	// Install the Triggers with appropriate Sinks and filters
+	f.Setup("install trigger1", trigger.Install(
+		trigger1,
+		brokerName,
+		trigger.WithSubscriber(svc.AsKReference(sink1), ""),
+		trigger.WithFilter(map[string]string{"type": eventType1, "source": eventSource1}),
+	))
+	f.Setup("trigger1 goes ready", trigger.IsReady(trigger1))
+
+	f.Setup("install trigger2", trigger.Install(
+		trigger2,
+		brokerName,
+		trigger.WithSubscriber(svc.AsKReference(sink2), ""),
+		trigger.WithFilter(map[string]string{"type": eventType2, "source": eventSource2}),
+	))
+	f.Setup("trigger2 goes ready", trigger.IsReady(trigger2))
+
+	// Install the Source
+	f.Requirement("install source", eventshub.Install(
+		source,
+		eventshub.StartSenderToResource(broker.GVR(), brokerName),
+		eventshub.InputEvent(event),
+	))
+
+	f.Assert("receive long event on sink1 exactly once",
+		eventasssert.OnStore(sink1).
+			MatchEvent(test.HasData([]byte(eventBody))).
+			Exact(1),
+	)
+
+	f.Assert("receive long event on sink2 exactly once",
+		eventasssert.OnStore(sink2).
+			MatchEvent(test.HasData([]byte(transformedEventBody))).
+			Exact(1),
+	)
+
+	return f
+}