From af99b247f9525a46a9e20f3b8711c457fab73da2 Mon Sep 17 00:00:00 2001
From: Tim Vaillancourt <tim@timvaillancourt.com>
Date: Sat, 4 Jun 2022 23:59:00 +0200
Subject: [PATCH] Add `Migrated` changelog event

---
 go/logic/migrator.go | 31 ++++++++++++++++++++-----------
 1 file changed, 20 insertions(+), 11 deletions(-)

diff --git a/go/logic/migrator.go b/go/logic/migrator.go
index c5cb244..13108bc 100644
--- a/go/logic/migrator.go
+++ b/go/logic/migrator.go
@@ -24,8 +24,9 @@ import (
 type ChangelogState string
 
 const (
+	AllEventsUpToLockProcessed ChangelogState = "AllEventsUpToLockProcessed"
 	GhostTableMigrated         ChangelogState = "GhostTableMigrated"
-	AllEventsUpToLockProcessed                = "AllEventsUpToLockProcessed"
+	Migrated                   ChangelogState = "Migrated"
 )
 
 func ReadChangelogState(s string) ChangelogState {
@@ -215,6 +216,8 @@ func (this *Migrator) onChangelogStateEvent(dmlEvent *binlog.BinlogDMLEvent) (er
 	changelogState := ReadChangelogState(changelogStateString)
 	this.migrationContext.Log.Infof("Intercepted changelog state %s", changelogState)
 	switch changelogState {
+	case Migrated:
+		// no-op event
 	case GhostTableMigrated:
 		{
 			this.ghostTableMigrated <- true
@@ -534,19 +537,20 @@ func (this *Migrator) cutOver() (err error) {
 			}
 		}
 	}
-	if this.migrationContext.CutOverType == base.CutOverAtomic {
+
+	switch this.migrationContext.CutOverType {
+	case base.CutOverAtomic:
 		// Atomic solution: we use low timeout and multiple attempts. But for
 		// each failed attempt, we throttle until replication lag is back to normal
-		err := this.atomicCutOver()
-		this.handleCutOverResult(err)
-		return err
+		err = this.atomicCutOver()
+	case base.CutOverTwoStep:
+		err = this.cutOverTwoStep()
+	default:
+		return this.migrationContext.Log.Fatalf("Unknown cut-over type: %d; should never get here!", this.migrationContext.CutOverType)
 	}
-	if this.migrationContext.CutOverType == base.CutOverTwoStep {
-		err := this.cutOverTwoStep()
-		this.handleCutOverResult(err)
-		return err
-	}
-	return this.migrationContext.Log.Fatalf("Unknown cut-over type: %d; should never get here!", this.migrationContext.CutOverType)
+
+	this.handleCutOverResult(err)
+	return err
 }
 
 // Inject the "AllEventsUpToLockProcessed" state hint, wait for it to appear in the binary logs,
@@ -1296,6 +1300,11 @@ func (this *Migrator) executeWriteFuncs() error {
 func (this *Migrator) finalCleanup() error {
 	atomic.StoreInt64(&this.migrationContext.CleanupImminentFlag, 1)
 
+	this.migrationContext.Log.Infof("Writing changelog state: %+v", Migrated)
+	if _, err := this.applier.WriteChangelogState(string(Migrated)); err != nil {
+		return err
+	}
+
 	if this.migrationContext.Noop {
 		if createTableStatement, err := this.inspector.showCreateTable(this.migrationContext.GetGhostTableName()); err == nil {
 			this.migrationContext.Log.Infof("New table structure follows")