ticdc/mq: accurately demonstrate txn_batch_size metric for MQ sink (#…

…3609) (#3819)

* fix the txn_batch_size metric inaccuracy bug when the sink target is MQ

* address comments

* add comments for exported functions

* fix the compiling problem

* fix conflicts.

Co-authored-by: zhaoxinyu <zhaoxinyu512@gmail.com>
Co-authored-by: Ling Jin <7138436+3AceShowHand@users.noreply.github.com>
Co-authored-by: 3AceShowHand <jinl1037@hotmail.com>

cdc/sink/codec/craft.go

@@ -46,7 +46,10 @@ func (e *CraftEventBatchEncoder) flush() {
 	ts := headers.GetTs(0)
 	schema := headers.GetSchema(0)
 	table := headers.GetTable(0)
-	e.messageBuf = append(e.messageBuf, NewMQMessage(ProtocolCraft, nil, e.rowChangedBuffer.Encode(), ts, model.MqMessageTypeRow, &schema, &table))
+	rowsCnt := e.rowChangedBuffer.RowsCount()
+	mqMessage := NewMQMessage(ProtocolCraft, nil, e.rowChangedBuffer.Encode(), ts, model.MqMessageTypeRow, &schema, &table)
+	mqMessage.SetRowsCount(rowsCnt)
+	e.messageBuf = append(e.messageBuf, mqMessage)
 }
 
 // AppendRowChangedEvent implements the EventBatchEncoder interface

cdc/sink/codec/craft/model.go

@@ -498,6 +498,11 @@ func (b *RowChangedEventBuffer) Size() int {
 	return b.estimatedSize
 }
 
+// Number of rows batched in this buffer
+func (b *RowChangedEventBuffer) RowsCount() int {
+	return b.eventsCount
+}
+
 // GetHeaders returns headers of buffer
 func (b *RowChangedEventBuffer) GetHeaders() *Headers {
 	return b.headers

cdc/sink/codec/interface.go

@@ -57,13 +57,14 @@ type EventBatchEncoder interface {
 
 // MQMessage represents an MQ message to the mqSink
 type MQMessage struct {
-	Key      []byte
-	Value    []byte
-	Ts       uint64              // reserved for possible output sorting
-	Schema   *string             // schema
-	Table    *string             // table
-	Type     model.MqMessageType // type
-	Protocol Protocol            // protocol
+	Key       []byte
+	Value     []byte
+	Ts        uint64              // reserved for possible output sorting
+	Schema    *string             // schema
+	Table     *string             // table
+	Type      model.MqMessageType // type
+	Protocol  Protocol            // protocol
+	rowsCount int                 // rows in one MQ Message
 }
 
 // maximumRecordOverhead is used to calculate ProducerMessage's byteSize by sarama kafka client.
@@ -83,6 +84,21 @@ func (m *MQMessage) PhysicalTime() time.Time {
 	return oracle.GetTimeFromTS(m.Ts)
 }
 
+// GetRowsCount returns the number of rows batched in one MQMessage
+func (m *MQMessage) GetRowsCount() int {
+	return m.rowsCount
+}
+
+// SetRowsCount set the number of rows
+func (m *MQMessage) SetRowsCount(cnt int) {
+	m.rowsCount = cnt
+}
+
+// IncRowsCount increase the number of rows
+func (m *MQMessage) IncRowsCount() {
+	m.rowsCount++
+}
+
 func newDDLMQMessage(proto Protocol, key, value []byte, event *model.DDLEvent) *MQMessage {
 	return NewMQMessage(proto, key, value, event.CommitTs, model.MqMessageTypeDDL, &event.TableInfo.Schema, &event.TableInfo.Table)
 }
@@ -95,13 +111,14 @@ func newResolvedMQMessage(proto Protocol, key, value []byte, ts uint64) *MQMessa
 // It copies the input byte slices to avoid any surprises in asynchronous MQ writes.
 func NewMQMessage(proto Protocol, key []byte, value []byte, ts uint64, ty model.MqMessageType, schema, table *string) *MQMessage {
 	ret := &MQMessage{
-		Key:      nil,
-		Value:    nil,
-		Ts:       ts,
-		Schema:   schema,
-		Table:    table,
-		Type:     ty,
-		Protocol: proto,
+		Key:       nil,
+		Value:     nil,
+		Ts:        ts,
+		Schema:    schema,
+		Table:     table,
+		Type:      ty,
+		Protocol:  proto,
+		rowsCount: 0,
 	}
 
 	if key != nil {

cdc/sink/codec/json.go

@@ -454,6 +454,7 @@ func (d *JSONEventBatchEncoder) AppendRowChangedEvent(e *model.RowChangedEvent)
 		message.Ts = e.CommitTs
 		message.Schema = &e.Table.Schema
 		message.Table = &e.Table.Table
+		message.IncRowsCount()
 
 		if message.Length() > d.maxMessageSize {
 			// `len(d.messageBuf) == 1` is implied

cdc/sink/mq.go

@@ -275,8 +275,8 @@ func (k *mqSink) runWorker(ctx context.Context, partition int32) error {
 	flushToProducer := func(op codec.EncoderResult) error {
 		return k.statistics.RecordBatchExecution(func() (int, error) {
 			messages := encoder.Build()
-			thisBatchSize := len(messages)
-			if thisBatchSize == 0 {
+			thisBatchSize := 0
+			if len(messages) == 0 {
 				return 0, nil
 			}
 
@@ -285,6 +285,7 @@ func (k *mqSink) runWorker(ctx context.Context, partition int32) error {
 				if err != nil {
 					return 0, err
 				}
+				thisBatchSize += msg.GetRowsCount()
 			}
 
 			if op == codec.EncoderNeedSyncWrite {