fix(client): Metadata refresh should skip updates when metadata respo…

…nse is empty

Fix #2664

We should skip the metadata refresh if the startup phase broker returns empty brokers in metadata response. The Java client skips the empty response to update the metadata cache (https://github.com/apache/kafka/blob/trunk/clients/src/main/java/org/apache/kafka/clients/NetworkClient.java#L1149) and we should make a feature parity in Sarama too

Signed-off-by: Hao Sun <[email protected]>

client.go

@@ -1035,6 +1035,13 @@ func (client *client) tryRefreshMetadata(topics []string, attemptsRemaining int,
 		var kerror KError
 		var packetEncodingError PacketEncodingError
 		if err == nil {
+			// When talking to the startup phase of a broker, it is possible to receive an empty metadata set. We should remove that broker and try next broker (https://issues.apache.org/jira/browse/KAFKA-7924).
+			if len(response.Brokers) == 0 {
+				Logger.Println("client/metadata receiving empty brokers from the metadata response when requesting the broker #%d at %s", broker.ID(), broker.addr)
+				_ = broker.Close()
+				client.deregisterBroker(broker)
+				continue
+			}
 			allKnownMetaData := len(topics) == 0
 			// valid response, use it
 			shouldRetry, err := client.updateMetadata(response, allKnownMetaData)

client_test.go

@@ -23,7 +23,9 @@ func safeClose(t testing.TB, c io.Closer) {
 func TestSimpleClient(t *testing.T) {
 	seedBroker := NewMockBroker(t, 1)
 
-	seedBroker.Returns(new(MetadataResponse))
+	metadataResponse := new(MetadataResponse)
+	metadataResponse.AddBroker(seedBroker.Addr(), seedBroker.BrokerID())
+	seedBroker.Returns(metadataResponse)
 
 	client, err := NewClient([]string{seedBroker.Addr()}, NewTestConfig())
 	if err != nil {
@@ -92,6 +94,7 @@ func TestClientDoesntCachePartitionsForTopicsWithErrors(t *testing.T) {
 	}
 
 	metadataResponse = new(MetadataResponse)
+	metadataResponse.AddBroker(seedBroker.Addr(), seedBroker.BrokerID())
 	metadataResponse.AddTopic("unknown", ErrUnknownTopicOrPartition)
 	seedBroker.Returns(metadataResponse)
 
@@ -111,6 +114,7 @@ func TestClientDoesntCachePartitionsForTopicsWithErrors(t *testing.T) {
 	}
 
 	metadataResponse = new(MetadataResponse)
+	metadataResponse.AddBroker(seedBroker.Addr(), seedBroker.BrokerID())
 	metadataResponse.AddTopic("unknown", ErrUnknownTopicOrPartition)
 	seedBroker.Returns(metadataResponse)
 
@@ -358,6 +362,7 @@ func TestClientReceivingUnknownTopicWithBackoffFunc(t *testing.T) {
 	seedBroker := NewMockBroker(t, 1)
 
 	metadataResponse1 := new(MetadataResponse)
+	metadataResponse1.AddBroker(seedBroker.Addr(), seedBroker.BrokerID())
 	seedBroker.Returns(metadataResponse1)
 
 	retryCount := int32(0)
@@ -375,6 +380,7 @@ func TestClientReceivingUnknownTopicWithBackoffFunc(t *testing.T) {
 
 	metadataUnknownTopic := new(MetadataResponse)
 	metadataUnknownTopic.AddTopic("new_topic", ErrUnknownTopicOrPartition)
+	metadataUnknownTopic.AddBroker(seedBroker.Addr(), seedBroker.BrokerID())
 	seedBroker.Returns(metadataUnknownTopic)
 	seedBroker.Returns(metadataUnknownTopic)
 
@@ -395,6 +401,7 @@ func TestClientReceivingUnknownTopic(t *testing.T) {
 	seedBroker := NewMockBroker(t, 1)
 
 	metadataResponse1 := new(MetadataResponse)
+	metadataResponse1.AddBroker(seedBroker.Addr(), seedBroker.BrokerID())
 	seedBroker.Returns(metadataResponse1)
 
 	config := NewTestConfig()
@@ -406,6 +413,7 @@ func TestClientReceivingUnknownTopic(t *testing.T) {
 	}
 
 	metadataUnknownTopic := new(MetadataResponse)
+	metadataUnknownTopic.AddBroker(seedBroker.Addr(), seedBroker.BrokerID())
 	metadataUnknownTopic.AddTopic("new_topic", ErrUnknownTopicOrPartition)
 	seedBroker.Returns(metadataUnknownTopic)
 	seedBroker.Returns(metadataUnknownTopic)
@@ -481,6 +489,53 @@ func TestClientReceivingPartialMetadata(t *testing.T) {
 	leader.Close()
 }
 
+func TestClientRefreshBehaviourWhenEmptyMetadataResponse(t *testing.T) {
+	seedBroker := NewMockBroker(t, 1)
+	broker := NewMockBroker(t, 2)
+
+	metadataResponse1 := new(MetadataResponse)
+	metadataResponse1.AddBroker(seedBroker.Addr(), seedBroker.BrokerID())
+	seedBroker.Returns(metadataResponse1)
+
+	c, err := NewClient([]string{seedBroker.Addr()}, NewTestConfig())
+	if err != nil {
+		t.Fatal(err)
+	}
+	client := c.(*client)
+	if len(client.seedBrokers) != 1 {
+		t.Error("incorrect number of live seeds")
+	}
+	if len(client.deadSeeds) != 0 {
+		t.Error("incorrect number of dead seeds")
+	}
+	if len(client.brokers) != 1 {
+		t.Error("incorrect number of brokers")
+	}
+
+	// Empty metadata response
+	seedBroker.Returns(new(MetadataResponse))
+	metadataResponse2 := new(MetadataResponse)
+	metadataResponse2.AddBroker(seedBroker.Addr(), seedBroker.BrokerID())
+	metadataResponse2.AddBroker(broker.Addr(), broker.BrokerID())
+	seedBroker.Returns(metadataResponse2)
+	err = c.RefreshMetadata()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(client.seedBrokers) != 1 {
+		t.Error("incorrect number of live seeds")
+	}
+	if len(client.deadSeeds) != 0 {
+		t.Error("incorrect number of dead seeds")
+	}
+	if len(client.brokers) != 2 {
+		t.Error("incorrect number of brokers")
+	}
+	broker.Close()
+	seedBroker.Close()
+	safeClose(t, client)
+}
+
 func TestClientRefreshBehaviour(t *testing.T) {
 	seedBroker := NewMockBroker(t, 1)
 	leader := NewMockBroker(t, 5)
@@ -633,8 +688,9 @@ func TestClientGetBroker(t *testing.T) {
 
 func TestClientResurrectDeadSeeds(t *testing.T) {
 	initialSeed := NewMockBroker(t, 0)
-	emptyMetadata := new(MetadataResponse)
-	initialSeed.Returns(emptyMetadata)
+	metadataResponse := new(MetadataResponse)
+	metadataResponse.AddBroker(initialSeed.Addr(), initialSeed.BrokerID())
+	initialSeed.Returns(metadataResponse)
 
 	conf := NewTestConfig()
 	conf.Metadata.Retry.Backoff = 0
@@ -643,7 +699,6 @@ func TestClientResurrectDeadSeeds(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	initialSeed.Close()
 
 	client := c.(*client)
 
@@ -658,6 +713,7 @@ func TestClientResurrectDeadSeeds(t *testing.T) {
 	safeClose(t, client.seedBrokers[0])
 	client.seedBrokers = []*Broker{NewBroker(addr1), NewBroker(addr2), NewBroker(addr3)}
 	client.deadSeeds = []*Broker{}
+	client.brokers = map[int32]*Broker{}
 
 	wg := sync.WaitGroup{}
 	wg.Add(1)
@@ -676,7 +732,9 @@ func TestClientResurrectDeadSeeds(t *testing.T) {
 	seed3.Close()
 
 	seed1.Close()
-	seed2.Returns(emptyMetadata)
+	metadataResponse2 := new(MetadataResponse)
+	metadataResponse2.AddBroker(seed2.Addr(), seed2.BrokerID())
+	seed2.Returns(metadataResponse2)
 
 	wg.Wait()
 
@@ -767,6 +825,7 @@ func TestClientMetadataTimeout(t *testing.T) {
 			// Use a responsive broker to create a working client
 			initialSeed := NewMockBroker(t, 0)
 			emptyMetadata := new(MetadataResponse)
+			emptyMetadata.AddBroker(initialSeed.Addr(), initialSeed.BrokerID())
 			initialSeed.Returns(emptyMetadata)
 
 			conf := NewTestConfig()
@@ -996,6 +1055,7 @@ func TestClientCoordinatorWithoutConsumerOffsetsTopic(t *testing.T) {
 	coordinator := NewMockBroker(t, 2)
 
 	metadataResponse1 := new(MetadataResponse)
+	metadataResponse1.AddBroker(seedBroker.Addr(), seedBroker.BrokerID())
 	seedBroker.Returns(metadataResponse1)
 
 	config := NewTestConfig()
@@ -1011,11 +1071,13 @@ func TestClientCoordinatorWithoutConsumerOffsetsTopic(t *testing.T) {
 	seedBroker.Returns(coordinatorResponse1)
 
 	metadataResponse2 := new(MetadataResponse)
+	metadataResponse2.AddBroker(seedBroker.Addr(), seedBroker.BrokerID())
 	metadataResponse2.AddTopic("__consumer_offsets", ErrUnknownTopicOrPartition)
 	seedBroker.Returns(metadataResponse2)
 
 	replicas := []int32{coordinator.BrokerID()}
 	metadataResponse3 := new(MetadataResponse)
+	metadataResponse3.AddBroker(seedBroker.Addr(), seedBroker.BrokerID())
 	metadataResponse3.AddTopicPartition("__consumer_offsets", 0, replicas[0], replicas, replicas, []int32{}, ErrNoError)
 	seedBroker.Returns(metadataResponse3)
 
@@ -1049,6 +1111,7 @@ func TestClientAutorefreshShutdownRace(t *testing.T) {
 	defer seedBroker.Close()
 
 	metadataResponse := new(MetadataResponse)
+	metadataResponse.AddBroker(seedBroker.Addr(), seedBroker.BrokerID())
 	seedBroker.Returns(metadataResponse)
 
 	conf := NewTestConfig()
@@ -1105,7 +1168,9 @@ func TestClientConnectionRefused(t *testing.T) {
 func TestClientCoordinatorConnectionRefused(t *testing.T) {
 	t.Parallel()
 	seedBroker := NewMockBroker(t, 1)
-	seedBroker.Returns(new(MetadataResponse))
+	metadataResponse := new(MetadataResponse)
+	metadataResponse.AddBroker(seedBroker.Addr(), seedBroker.BrokerID())
+	seedBroker.Returns(metadataResponse)
 
 	client, err := NewClient([]string{seedBroker.Addr()}, NewTestConfig())
 	if err != nil {
@@ -1130,7 +1195,10 @@ func TestClientCoordinatorConnectionRefused(t *testing.T) {
 func TestInitProducerIDConnectionRefused(t *testing.T) {
 	t.Parallel()
 	seedBroker := NewMockBroker(t, 1)
-	seedBroker.Returns(&MetadataResponse{Version: 4})
+	metadataResponse := new(MetadataResponse)
+	metadataResponse.AddBroker(seedBroker.Addr(), seedBroker.BrokerID())
+	metadataResponse.Version = 4
+	seedBroker.Returns(metadataResponse)
 
 	config := NewTestConfig()
 	config.Producer.Idempotent = true
@@ -1161,7 +1229,9 @@ func TestInitProducerIDConnectionRefused(t *testing.T) {
 func TestMetricsCleanup(t *testing.T) {
 	seedBroker := NewMockBroker(t, 1)
 	defer seedBroker.Close()
-	seedBroker.Returns(new(MetadataResponse))
+	metadataResponse := new(MetadataResponse)
+	metadataResponse.AddBroker(seedBroker.Addr(), seedBroker.BrokerID())
+	seedBroker.Returns(metadataResponse)
 
 	config := NewTestConfig()
 	metrics.GetOrRegisterMeter("a", config.MetricRegistry)

client_tls_test.go

@@ -197,7 +197,9 @@ func doListenerTLSTest(t *testing.T, expectSuccess bool, serverConfig, clientCon
 	seedBroker := NewMockBrokerListener(childT, 1, seedListener)
 	defer seedBroker.Close()
 
-	seedBroker.Returns(new(MetadataResponse))
+	metadataResponse := new(MetadataResponse)
+	metadataResponse.AddBroker(seedBroker.Addr(), seedBroker.BrokerID())
+	seedBroker.Returns(metadataResponse)
 
 	config := NewTestConfig()
 	config.Net.TLS.Enable = true

offset_manager_test.go

@@ -78,7 +78,9 @@ func initPartitionOffsetManager(t *testing.T, om OffsetManager,
 
 func TestNewOffsetManager(t *testing.T) {
 	seedBroker := NewMockBroker(t, 1)
-	seedBroker.Returns(new(MetadataResponse))
+	metadataResponse := new(MetadataResponse)
+	metadataResponse.AddBroker(seedBroker.Addr(), seedBroker.BrokerID())
+	seedBroker.Returns(metadataResponse)
 	defer seedBroker.Close()
 
 	testClient, err := NewClient([]string{seedBroker.Addr()}, NewTestConfig())

sync_producer_test.go

@@ -271,6 +271,7 @@ func TestSyncProducerToNonExistingTopic(t *testing.T) {
 	}
 
 	metadataResponse = new(MetadataResponse)
+	metadataResponse.AddBroker(broker.Addr(), broker.BrokerID())
 	metadataResponse.AddTopic("unknown", ErrUnknownTopicOrPartition)
 	broker.Returns(metadataResponse)