fix: stuck on the batch with zero records length

consumer.go

@@ -629,6 +629,10 @@ func (child *partitionConsumer) parseResponse(response *FetchResponse) ([]*Consu
 					child.fetchSize = child.conf.Consumer.Fetch.Max
 				}
 			}
+		} else if block.LastRecordsBatchOffset != nil && *block.LastRecordsBatchOffset < block.HighWaterMarkOffset {
+			// check last record offset to avoid stuck if high watermark was not reached
+			Logger.Printf("consumer/broker/%d received batch with zero records but high watermark was not reached, topic %s, partition %d, offset %d\n", child.broker.broker.ID(), child.topic, child.partition, *block.LastRecordsBatchOffset)
+			child.offset = *block.LastRecordsBatchOffset + 1
 		}
 
 		return nil, nil

consumer_test.go

@@ -1734,6 +1734,39 @@ func Test_partitionConsumer_parseResponse(t *testing.T) {
 	}
 }
 
+func Test_partitionConsumer_parseResponseEmptyBatch(t *testing.T) {
+	lrbOffset := int64(5)
+	block := &FetchResponseBlock{
+		HighWaterMarkOffset:    10,
+		LastStableOffset:       10,
+		LastRecordsBatchOffset: &lrbOffset,
+		LogStartOffset:         0,
+	}
+	response := &FetchResponse{
+		Blocks:  map[string]map[int32]*FetchResponseBlock{"my_topic": {0: block}},
+		Version: 2,
+	}
+	child := &partitionConsumer{
+		broker: &brokerConsumer{
+			broker: &Broker{},
+		},
+		conf:      NewConfig(),
+		topic:     "my_topic",
+		partition: 0,
+	}
+	got, err := child.parseResponse(response)
+	if err != nil {
+		t.Errorf("partitionConsumer.parseResponse() error = %v", err)
+		return
+	}
+	if got != nil {
+		t.Errorf("partitionConsumer.parseResponse() should be nil, got %v", got)
+	}
+	if child.offset != 6 {
+		t.Errorf("child.offset should be LastRecordsBatchOffset + 1: %d, got %d", lrbOffset+1, child.offset)
+	}
+}
+
 func testConsumerInterceptor(
 	t *testing.T,
 	interceptors []ConsumerInterceptor,

fetch_response.go

@@ -30,15 +30,16 @@ func (t *AbortedTransaction) encode(pe packetEncoder) (err error) {
 }
 
 type FetchResponseBlock struct {
-	Err                  KError
-	HighWaterMarkOffset  int64
-	LastStableOffset     int64
-	LogStartOffset       int64
-	AbortedTransactions  []*AbortedTransaction
-	PreferredReadReplica int32
-	Records              *Records // deprecated: use FetchResponseBlock.RecordsSet
-	RecordsSet           []*Records
-	Partial              bool
+	Err                    KError
+	HighWaterMarkOffset    int64
+	LastStableOffset       int64
+	LastRecordsBatchOffset *int64
+	LogStartOffset         int64
+	AbortedTransactions    []*AbortedTransaction
+	PreferredReadReplica   int32
+	Records                *Records // deprecated: use FetchResponseBlock.RecordsSet
+	RecordsSet             []*Records
+	Partial                bool
 }
 
 func (b *FetchResponseBlock) decode(pd packetDecoder, version int16) (err error) {
@@ -118,6 +119,11 @@ func (b *FetchResponseBlock) decode(pd packetDecoder, version int16) (err error)
 			return err
 		}
 
+		b.LastRecordsBatchOffset, err = records.recordsOffset()
+		if err != nil {
+			return err
+		}
+
 		partial, err := records.isPartial()
 		if err != nil {
 			return err

fetch_response_test.go

@@ -121,6 +121,37 @@ var (
 		0x00,
 	}
 
+	emptyRecordsFetchResponsev11 = []byte{
+		0x00, 0x00, 0x00, 0x00, // ThrottleTime
+		0x00, 0x00, // Error
+		0x00, 0x00, 0x00, 0x00, // Fetch session
+		0x00, 0x00, 0x00, 0x01, // Num topic
+		0x00, 0x05, 't', 'o', 'p', 'i', 'c', // Topic
+		0x00, 0x00, 0x00, 0x01, // Num partition
+		0x00, 0x00, 0x00, 0x05, // Partition
+		0x00, 0x00, // Error
+		0x00, 0x00, 0x00, 0x00, 0x10, 0x10, 0x10, 0x10, // High Watermark Offset
+		0x00, 0x00, 0x00, 0x00, 0x10, 0x10, 0x10, 0x10, // Last Stable Offset
+		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // Log start offset
+		0x00, 0x00, 0x00, 0x00, // Number of Aborted Transactions
+		0xff, 0xff, 0xff, 0xff, // Replica id
+		0x00, 0x00, 0x00, 0x3D, // Batch size
+		// recordBatch
+		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // Offset
+		0x00, 0x00, 0x00, 0x31, // Message size
+		0x00, 0x00, 0x00, 0x00, // Leader epoch
+		0x02,                   // Magic byte
+		0x14, 0xE0, 0x7A, 0x62, // CRC
+		0x00, 0x00, // Flags
+		0x00, 0x00, 0x00, 0x00, // Last offset delta
+		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x0A, // First timestamp
+		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x0B, // Last timestamp
+		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, // Producer id
+		0x00, 0x00, // Producer epoch
+		0x00, 0x00, 0x00, 0x3d, // Base sequence
+		0x00, 0x00, 0x00, 0x00, // Records size
+	}
+
 	oneMessageFetchResponseV4 = []byte{
 		0x00, 0x00, 0x00, 0x00, // ThrottleTime
 		0x00, 0x00, 0x00, 0x01, // Number of Topics
@@ -386,6 +417,51 @@ func TestPartailFetchResponse(t *testing.T) {
 	}
 }
 
+func TestEmptyRecordsFetchResponse(t *testing.T) {
+	response := FetchResponse{}
+	testVersionDecodable(t, "empty record", &response, emptyRecordsFetchResponsev11, 11)
+
+	if len(response.Blocks) != 1 {
+		t.Fatal("Decoding produced incorrect number of topic blocks.")
+	}
+
+	if len(response.Blocks["topic"]) != 1 {
+		t.Fatal("Decoding produced incorrect number of partition blocks for topic.")
+	}
+
+	block := response.GetBlock("topic", 5)
+	if block == nil {
+		t.Fatal("GetBlock didn't return block.")
+	}
+	if block.Err != ErrNoError {
+		t.Error("Decoding didn't produce correct error code.")
+	}
+	if block.HighWaterMarkOffset != 0x10101010 {
+		t.Error("Decoding didn't produce correct high water mark offset.")
+	}
+	if block.PreferredReadReplica != -1 {
+		t.Error("Decoding didn't produce correct preferred read replica.")
+	}
+	partial, err := block.isPartial()
+	if err != nil {
+		t.Fatalf("Unexpected error: %v", err)
+	}
+	if partial {
+		t.Error("Decoding a partial trailing record")
+	}
+
+	n, err := block.numRecords()
+	if err != nil {
+		t.Fatalf("Unexpected error: %v", err)
+	}
+	if n != 0 {
+		t.Fatal("Decoding produced incorrect number of records.")
+	}
+	if *block.LastRecordsBatchOffset != 0 {
+		t.Fatal("Last records batch offset is incorrect.")
+	}
+}
+
 func TestOneMessageFetchResponseV4(t *testing.T) {
 	response := FetchResponse{}
 	testVersionDecodable(t, "one message v4", &response, oneMessageFetchResponseV4, 4)

records.go

@@ -183,6 +183,21 @@ func (r *Records) isOverflow() (bool, error) {
 	return false, fmt.Errorf("unknown records type: %v", r.recordsType)
 }
 
+func (r *Records) recordsOffset() (*int64, error) {
+	switch r.recordsType {
+	case unknownRecords:
+		return nil, nil
+	case legacyRecords:
+		return nil, nil
+	case defaultRecords:
+		if r.RecordBatch == nil {
+			return nil, nil
+		}
+		return &r.RecordBatch.FirstOffset, nil
+	}
+	return nil, fmt.Errorf("unknown records type: %v", r.recordsType)
+}
+
 func magicValue(pd packetDecoder) (int8, error) {
 	return pd.peekInt8(magicOffset)
 }

records_test.go

@@ -72,12 +72,20 @@ func TestLegacyRecords(t *testing.T) {
 	if c {
 		t.Errorf("MessageSet can't be a control batch")
 	}
+	f, err := r.recordsOffset()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if f != nil {
+		t.Errorf("RecordBatch record offset is invalid")
+	}
 }
 
 func TestDefaultRecords(t *testing.T) {
 	batch := &RecordBatch{
 		IsTransactional: true,
 		Version:         2,
+		FirstOffset:     1,
 		Records: []*Record{
 			{
 				Value: []byte{1},
@@ -141,4 +149,11 @@ func TestDefaultRecords(t *testing.T) {
 	if c {
 		t.Errorf("RecordBatch shouldn't be a control batch")
 	}
+	f, err := r.recordsOffset()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if f == nil || *f != 1 {
+		t.Errorf("RecordBatch record offset is invalid")
+	}
 }