Add a optional function to decode optional meta of table map event (#833)

* lower memory usage by reducing event chan size in streamer

When consuming events from stream is blocked, the chan may use too much memory

* make streamer's event chan size configurable

When the consumption speed of the event chan in streamer cannot catch up with its production speed, leading to an accumulation of events, the current fixed channel size of 10240 might occupy significant memory, potentially triggering an Out Of Memory (OOM) condition. Making the size of the event chan configurable would allow for controlling the memory usage of the streamer.

* update cfg name StreamerChanSize to EventCacheSize

* EventCacheSize is renamed to EventCacheCount, to make the variable name more reflective of its actual meaning.

* Add a optional function to decode optional meta of table map event

Author: zing22845

replication/binlogsyncer.go

@@ -121,6 +121,8 @@ type BinlogSyncerConfig struct {
 
 	RowsEventDecodeFunc func(*RowsEvent, []byte) error
 
+	TableMapOptionalMetaDecodeFunc func([]byte) error
+
 	DiscardGTIDSet bool
 
 	EventCacheCount int
@@ -189,6 +191,7 @@ func NewBinlogSyncer(cfg BinlogSyncerConfig) *BinlogSyncer {
 	b.parser.SetUseDecimal(b.cfg.UseDecimal)
 	b.parser.SetVerifyChecksum(b.cfg.VerifyChecksum)
 	b.parser.SetRowsEventDecodeFunc(b.cfg.RowsEventDecodeFunc)
+	b.parser.SetTableMapOptionalMetaDecodeFunc(b.cfg.TableMapOptionalMetaDecodeFunc)
 	b.running = false
 	b.ctx, b.cancel = context.WithCancel(context.Background())
 

replication/parser.go

@@ -42,6 +42,8 @@ type BinlogParser struct {
 	verifyChecksum      bool
 
 	rowsEventDecodeFunc func(*RowsEvent, []byte) error
+
+	tableMapOptionalMetaDecodeFunc func([]byte) error
 }
 
 func NewBinlogParser() *BinlogParser {
@@ -218,6 +220,10 @@ func (p *BinlogParser) SetRowsEventDecodeFunc(rowsEventDecodeFunc func(*RowsEven
 	p.rowsEventDecodeFunc = rowsEventDecodeFunc
 }
 
+func (p *BinlogParser) SetTableMapOptionalMetaDecodeFunc(tableMapOptionalMetaDecondeFunc func([]byte) error) {
+	p.tableMapOptionalMetaDecodeFunc = tableMapOptionalMetaDecondeFunc
+}
+
 func (p *BinlogParser) parseHeader(data []byte) (*EventHeader, error) {
 	h := new(EventHeader)
 	err := h.Decode(data)
@@ -257,7 +263,8 @@ func (p *BinlogParser) parseEvent(h *EventHeader, data []byte, rawData []byte) (
 				e = &XIDEvent{}
 			case TABLE_MAP_EVENT:
 				te := &TableMapEvent{
-					flavor: p.flavor,
+					flavor:                 p.flavor,
+					optionalMetaDecodeFunc: p.tableMapOptionalMetaDecodeFunc,
 				}
 				if p.format.EventTypeHeaderLengths[TABLE_MAP_EVENT-1] == 6 {
 					te.tableIDSize = 4

replication/row_event.go

@@ -84,6 +84,8 @@ type TableMapEvent struct {
 
 	// VisibilityBitmap stores bits that are set if corresponding column is not invisible (MySQL 8.0.23+)
 	VisibilityBitmap []byte
+
+	optionalMetaDecodeFunc func(data []byte) (err error)
 }
 
 func (e *TableMapEvent) Decode(data []byte) error {
@@ -140,8 +142,14 @@ func (e *TableMapEvent) Decode(data []byte) error {
 
 	pos += nullBitmapSize
 
-	if err = e.decodeOptionalMeta(data[pos:]); err != nil {
-		return err
+	if e.optionalMetaDecodeFunc != nil {
+		if err = e.optionalMetaDecodeFunc(data[pos:]); err != nil {
+			return err
+		}
+	} else {
+		if err = e.decodeOptionalMeta(data[pos:]); err != nil {
+			return err
+		}
 	}
 
 	return nil