Handle upgrade/downgrade for vtorc

Signed-off-by: Matt Lord <mattalord@gmail.com>

go/vt/vtorc/inst/binlog.go

@@ -44,7 +44,8 @@ type BinlogCoordinates struct {
 	Type    BinlogType
 }
 
-// ParseInstanceKey will parse an InstanceKey from a string representation such as 127.0.0.1:3306
+// ParseBinlogCoordinates will parse a string representation such as "mysql-bin.000001:12345"
+// into a BinlogCoordinates struct.
 func ParseBinlogCoordinates(logFileLogPos string) (*BinlogCoordinates, error) {
 	tokens := strings.SplitN(logFileLogPos, ":", 2)
 	if len(tokens) != 2 {

go/vt/vtorc/inst/instance_dao.go

@@ -281,8 +281,7 @@ func ReadTopologyInstanceBufferable(tabletAlias string, latency *stopwatch.Named
 		errorChan <- err
 		instance.IsDetached, _ = instance.ExecBinlogCoordinates.ExtractDetachedCoordinates()
 
-		tbp, err := ParseBinlogCoordinates(fs.ReplicationStatus.RelayLogFilePosition)
-		binlogPos = *tbp
+		binlogPos, err = getBinlogCoordinatesFromString(fs.ReplicationStatus.FilePosition)
 		instance.RelaylogCoordinates = binlogPos
 		instance.RelaylogCoordinates.Type = RelayLog
 		errorChan <- err
@@ -451,6 +450,21 @@ func getKeyspaceShardName(keyspace, shard string) string {
 	return fmt.Sprintf("%v:%v", keyspace, shard)
 }
 
+// getBinlogCoordinatesFromString is a bridge function to support upgrades and
+// downgrades when a given string may be in one of two formats depending on
+// the component versions:
+//  1. GTID position, e.g. FilePos/relay-bin.000001:12345
+//  2. A simple binlog file position, e.g. relay-bin.000001:12345
+func getBinlogCoordinatesFromString(s string) (BinlogCoordinates, error) {
+	if strings.Contains(s, "/") {
+		// We have a GTID position which includes the flavor.
+		return getBinlogCoordinatesFromPositionString(s)
+	}
+	// We have a simple binlog file position.
+	binLogCoordinates, err := ParseBinlogCoordinates(s)
+	return *binLogCoordinates, err
+}
+
 func getBinlogCoordinatesFromPositionString(position string) (BinlogCoordinates, error) {
 	pos, err := replication.DecodePosition(position)
 	if err != nil || pos.GTIDSet == nil {