Make semi sync extension optional

go/mysql/flavor.go

@@ -71,7 +71,7 @@ type flavor interface {
 
 	// resetReplicationCommands returns the commands to completely reset
 	// replication on the host.
-	resetReplicationCommands() []string
+	resetReplicationCommands(c *Conn) []string
 
 	// setSlavePositionCommands returns the commands to set the
 	// replication position at which the slave will resume.
@@ -191,7 +191,7 @@ func (c *Conn) ReadBinlogEvent() (BinlogEvent, error) {
 // ResetReplicationCommands returns the commands to completely reset
 // replication on the host.
 func (c *Conn) ResetReplicationCommands() []string {
-	return c.flavor.resetReplicationCommands()
+	return c.flavor.resetReplicationCommands(c)
 }
 
 // SetSlavePositionCommands returns the commands to set the

go/mysql/flavor_filepos.go

@@ -164,7 +164,7 @@ func (flv *filePosFlavor) readBinlogEvent(c *Conn) (BinlogEvent, error) {
 }
 
 // resetReplicationCommands is part of the Flavor interface.
-func (flv *filePosFlavor) resetReplicationCommands() []string {
+func (flv *filePosFlavor) resetReplicationCommands(c *Conn) []string {
 	return []string{
 		"unsupported",
 	}

go/mysql/flavor_mariadb.go

@@ -83,14 +83,17 @@ func (mariadbFlavor) sendBinlogDumpCommand(c *Conn, slaveID uint32, startPos Pos
 }
 
 // resetReplicationCommands is part of the Flavor interface.
-func (mariadbFlavor) resetReplicationCommands() []string {
-	return []string{
+func (mariadbFlavor) resetReplicationCommands(c *Conn) []string {
+	resetCommands := []string{
 		"STOP SLAVE",
 		"RESET SLAVE ALL", // "ALL" makes it forget master host:port.
 		"RESET MASTER",
 		"SET GLOBAL gtid_slave_pos = ''",
-		"SET GLOBAL rpl_semi_sync_master_enabled = false, GLOBAL rpl_semi_sync_slave_enabled = false", // semi-sync will be enabled if needed when slave is started.
 	}
+	if c.SemiSyncExtensionLoaded() {
+		resetCommands = append(resetCommands, "SET GLOBAL rpl_semi_sync_master_enabled = false, GLOBAL rpl_semi_sync_slave_enabled = false") // semi-sync will be enabled if needed when slave is started.
+	}
+	return resetCommands
 }
 
 // setSlavePositionCommands is part of the Flavor interface.

go/mysql/flavor_mysql.go

@@ -66,13 +66,16 @@ func (mysqlFlavor) sendBinlogDumpCommand(c *Conn, slaveID uint32, startPos Posit
 }
 
 // resetReplicationCommands is part of the Flavor interface.
-func (mysqlFlavor) resetReplicationCommands() []string {
-	return []string{
+func (mysqlFlavor) resetReplicationCommands(c *Conn) []string {
+	resetCommands := []string{
 		"STOP SLAVE",
 		"RESET SLAVE ALL", // "ALL" makes it forget master host:port.
 		"RESET MASTER",    // This will also clear gtid_executed and gtid_purged.
-		"SET GLOBAL rpl_semi_sync_master_enabled = false, GLOBAL rpl_semi_sync_slave_enabled = false", // semi-sync will be enabled if needed when slave is started.
 	}
+	if c.SemiSyncExtensionLoaded() {
+		resetCommands = append(resetCommands, "SET GLOBAL rpl_semi_sync_master_enabled = false, GLOBAL rpl_semi_sync_slave_enabled = false") // semi-sync will be enabled if needed when slave is started.
+	}
+	return resetCommands
 }
 
 // setSlavePositionCommands is part of the Flavor interface.

go/mysql/replication.go

@@ -67,3 +67,13 @@ func (c *Conn) WriteComBinlogDumpGTID(serverID uint32, binlogFilename string, bi
 	}
 	return nil
 }
+
+// SemiSyncExtensionLoaded checks if the semisync extension has been loaded.
+// It should work for both MariaDB and MySQL.
+func (c *Conn) SemiSyncExtensionLoaded() bool {
+	qr, err := c.ExecuteFetch("SHOW GLOBAL VARIABLES LIKE 'rpl_semi_sync%'", 10, false)
+	if err != nil {
+		return false
+	}
+	return len(qr.Rows) >= 1
+}