-postpone-cut-over-flag-file implies touching indicated file

Author: Shlomi Noach

go/base/utils.go

@@ -33,6 +33,15 @@ func FileExists(fileName string) bool {
 	return false
 }
 
+func TouchFile(fileName string) error {
+	f, err := os.OpenFile(fileName, os.O_APPEND|os.O_CREATE, 0755)
+	if err != nil {
+		return (err)
+	}
+	defer f.Close()
+	return nil
+}
+
 // StringContainsAll returns true if `s` contains all non empty given `substrings`
 // The function returns `false` if no non-empty arguments are given.
 func StringContainsAll(s string, substrings ...string) bool {

go/logic/migrator.go

@@ -281,6 +281,18 @@ func (this *Migrator) countTableRows() (err error) {
 	return countRowsFunc()
 }
 
+func (this *Migrator) createFlagFiles() (err error) {
+	if this.migrationContext.PostponeCutOverFlagFile != "" {
+		if !base.FileExists(this.migrationContext.PostponeCutOverFlagFile) {
+			if err := base.TouchFile(this.migrationContext.PostponeCutOverFlagFile); err != nil {
+				return err
+			}
+			log.Infof("Created postpone-cut-over-flag-file: %s", this.migrationContext.PostponeCutOverFlagFile)
+		}
+	}
+	return nil
+}
+
 // Migrate executes the complete migration logic. This is *the* major gh-ost function.
 func (this *Migrator) Migrate() (err error) {
 	log.Infof("Migrating %s.%s", sql.EscapeName(this.migrationContext.DatabaseName), sql.EscapeName(this.migrationContext.OriginalTableName))
@@ -312,6 +324,9 @@ func (this *Migrator) Migrate() (err error) {
 	if err := this.initiateApplier(); err != nil {
 		return err
 	}
+	if err := this.createFlagFiles(); err != nil {
+		return err
+	}
 
 	initialLag, _ := this.inspector.getReplicationLag()
 	log.Infof("Waiting for ghost table to be migrated. Current lag is %+v", initialLag)