Added logic to remove the triggers in case of error and created channel

Author: Gonlo2

go/logic/applier.go

@@ -649,17 +649,17 @@ func (this *Applier) DropTriggersOldTable() error {
 	prefix := this.makeTriggerPrefix()
 
 	dropDeleteTrigger := fmt.Sprintf(
-		"DROP /* gh-ost */ TRIGGER %s.`%s_del`",
+		"DROP /* gh-ost */ TRIGGER IF EXISTS %s.`%s_del`",
 		sql.EscapeName(this.migrationContext.DatabaseName),
 		prefix)
 
 	dropInsertTrigger := fmt.Sprintf(
-		"DROP /* gh-ost */ TRIGGER %s.`%s_ins`",
+		"DROP /* gh-ost */ TRIGGER IF EXISTS %s.`%s_ins`",
 		sql.EscapeName(this.migrationContext.DatabaseName),
 		prefix)
 
 	dropUpdateTrigger := fmt.Sprintf(
-		"DROP /* gh-ost */ TRIGGER %s.`%s_upd`",
+		"DROP /* gh-ost */ TRIGGER IF EXISTS %s.`%s_upd`",
 		sql.EscapeName(this.migrationContext.DatabaseName),
 		prefix)
 

go/logic/migrator.go

@@ -100,6 +100,7 @@ func NewMigrator(context *base.MigrationContext) *Migrator {
 		firstThrottlingCollected:       make(chan bool, 3),
 		rowCopyComplete:                make(chan error),
 		allEventsUpToLockProcessed:     make(chan string),
+		stoppedBinlogWrites:            make(chan bool),
 		allEventsUpToTriggersProcessed: make(chan string),
 
 		copyRowsQueue:          make(chan tableWriteFunc),
@@ -692,6 +693,8 @@ func (this *Migrator) cutOverTrigger() (err error) {
 
 	this.waitForStopWrites()
 
+	defer this.applier.DropTriggersOldTable()
+
 	log.Infof(
 		"Creating triggers for %s.%s",
 		this.migrationContext.DatabaseName,