refactor cutover for MySQL 8.x rename feature && support OceanBase

Author: whhe

go/base/context.go

@@ -102,6 +102,7 @@ type MigrationContext struct {
 	GoogleCloudPlatform      bool
 	AzureMySQL               bool
 	AttemptInstantDDL        bool
+	OceanBase                bool
 
 	// SkipPortValidation allows skipping the port validation in `ValidateConnection`
 	// This is useful when connecting to a MySQL instance where the external port

go/base/utils.go

@@ -84,7 +84,7 @@ func ValidateConnection(db *gosql.DB, connectionConfig *mysql.ConnectionConfig,
 	// GCP set users port to "NULL", replace it by gh-ost param
 	// Azure MySQL set users port to a different value by design, replace it by gh-ost para
 	var port int
-	if migrationContext.AliyunRDS || migrationContext.GoogleCloudPlatform || migrationContext.AzureMySQL {
+	if migrationContext.AliyunRDS || migrationContext.GoogleCloudPlatform || migrationContext.AzureMySQL || migrationContext.OceanBase {
 		port = connectionConfig.Key.Port
 	} else {
 		portQuery := `select @@global.port`

go/cmd/gh-ost/main.go

@@ -86,6 +86,7 @@ func main() {
 	flag.BoolVar(&migrationContext.AliyunRDS, "aliyun-rds", false, "set to 'true' when you execute on Aliyun RDS.")
 	flag.BoolVar(&migrationContext.GoogleCloudPlatform, "gcp", false, "set to 'true' when you execute on a 1st generation Google Cloud Platform (GCP).")
 	flag.BoolVar(&migrationContext.AzureMySQL, "azure", false, "set to 'true' when you execute on Azure Database on MySQL.")
+	flag.BoolVar(&migrationContext.OceanBase, "oceanbase", false, "set to 'true' when you execute on OceanBase")
 
 	executeFlag := flag.Bool("execute", false, "actually execute the alter & migrate the table. Default is noop: do some tests and exit")
 	flag.BoolVar(&migrationContext.TestOnReplica, "test-on-replica", false, "Have the migration run on a replica, not on the master. At the end of migration replication is stopped, and tables are swapped and immediately swap-revert. Replication remains stopped and you can compare the two tables for building trust")

go/logic/applier.go

@@ -100,7 +100,7 @@ func (this *Applier) InitDBConnections() (err error) {
 	if err := this.validateAndReadGlobalVariables(); err != nil {
 		return err
 	}
-	if !this.migrationContext.AliyunRDS && !this.migrationContext.GoogleCloudPlatform && !this.migrationContext.AzureMySQL {
+	if !this.migrationContext.AliyunRDS && !this.migrationContext.GoogleCloudPlatform && !this.migrationContext.AzureMySQL && !this.migrationContext.OceanBase {
 		if impliedKey, err := mysql.GetInstanceKey(this.db); err != nil {
 			return err
 		} else {
@@ -714,24 +714,28 @@ func (this *Applier) ApplyIterationInsertQuery() (chunkSize int64, rowsAffected
 	return chunkSize, rowsAffected, duration, nil
 }
 
-// LockOriginalTable places a write lock on the original table
-func (this *Applier) LockOriginalTable() error {
-	query := fmt.Sprintf(`lock /* gh-ost */ tables %s.%s write`,
-		sql.EscapeName(this.migrationContext.DatabaseName),
-		sql.EscapeName(this.migrationContext.OriginalTableName),
-	)
-	this.migrationContext.Log.Infof("Locking %s.%s",
-		sql.EscapeName(this.migrationContext.DatabaseName),
-		sql.EscapeName(this.migrationContext.OriginalTableName),
-	)
+// lockTable places a write lock on the specific table
+func (this *Applier) lockTable(databaseName, tableName string) error {
+	query := fmt.Sprintf(`lock /* gh-ost */ tables %s.%s write`, databaseName, tableName)
+	this.migrationContext.Log.Infof("Locking %s.%s", databaseName, tableName)
 	this.migrationContext.LockTablesStartTime = time.Now()
 	if _, err := sqlutils.ExecNoPrepare(this.singletonDB, query); err != nil {
 		return err
 	}
-	this.migrationContext.Log.Infof("Table locked")
+	this.migrationContext.Log.Infof("Table %s.%s locked", databaseName, tableName)
 	return nil
 }
 
+// LockOriginalTable places a write lock on the original table
+func (this *Applier) LockOriginalTable() error {
+	return this.lockTable(this.migrationContext.DatabaseName, this.migrationContext.OriginalTableName)
+}
+
+// LockGhostTable places a write lock on the ghost table
+func (this *Applier) LockGhostTable() error {
+	return this.lockTable(this.migrationContext.DatabaseName, this.migrationContext.GetGhostTableName())
+}
+
 // UnlockTables makes tea. No wait, it unlocks tables.
 func (this *Applier) UnlockTables() error {
 	query := `unlock /* gh-ost */ tables`
@@ -1033,7 +1037,7 @@ func (this *Applier) AtomicCutOverMagicLock(sessionIdChan chan int64, tableLocke
 
 	tableLockTimeoutSeconds := this.migrationContext.CutOverLockTimeoutSeconds * 2
 	this.migrationContext.Log.Infof("Setting LOCK timeout as %d seconds", tableLockTimeoutSeconds)
-	query = fmt.Sprintf(`set /* gh-ost */ session lock_wait_timeout:=%d`, tableLockTimeoutSeconds)
+	query = fmt.Sprintf(`set /* gh-ost */ session lock_wait_timeout=%d`, tableLockTimeoutSeconds)
 	if _, err := tx.Exec(query); err != nil {
 		tableLocked <- err
 		return err
@@ -1108,25 +1112,31 @@ func (this *Applier) AtomicCutOverMagicLock(sessionIdChan chan int64, tableLocke
 	return nil
 }
 
-// AtomicCutoverRename
-func (this *Applier) AtomicCutoverRename(sessionIdChan chan int64, tablesRenamed chan<- error) error {
-	tx, err := this.db.Begin()
+func (this *Applier) atomicCutoverRename(db *gosql.DB, sessionIdChan chan int64, tablesRenamed chan<- error) error {
+	tx, err := db.Begin()
 	if err != nil {
 		return err
 	}
 	defer func() {
 		tx.Rollback()
-		sessionIdChan <- -1
-		tablesRenamed <- fmt.Errorf("Unexpected error in AtomicCutoverRename(), injected to release blocking channel reads")
+		if sessionIdChan != nil {
+			sessionIdChan <- -1
+		}
+		if tablesRenamed != nil {
+			tablesRenamed <- fmt.Errorf("Unexpected error in AtomicCutoverRename(), injected to release blocking channel reads")
+		}
 	}()
-	var sessionId int64
-	if err := tx.QueryRow(`select /* gh-ost */ connection_id()`).Scan(&sessionId); err != nil {
-		return err
+
+	if sessionIdChan != nil {
+		var sessionId int64
+		if err := tx.QueryRow(`select /* gh-ost */ connection_id()`).Scan(&sessionId); err != nil {
+			return err
+		}
+		sessionIdChan <- sessionId
 	}
-	sessionIdChan <- sessionId
 
 	this.migrationContext.Log.Infof("Setting RENAME timeout as %d seconds", this.migrationContext.CutOverLockTimeoutSeconds)
-	query := fmt.Sprintf(`set /* gh-ost */ session lock_wait_timeout:=%d`, this.migrationContext.CutOverLockTimeoutSeconds)
+	query := fmt.Sprintf(`set /* gh-ost */ session lock_wait_timeout=%d`, this.migrationContext.CutOverLockTimeoutSeconds)
 	if _, err := tx.Exec(query); err != nil {
 		return err
 	}
@@ -1143,14 +1153,28 @@ func (this *Applier) AtomicCutoverRename(sessionIdChan chan int64, tablesRenamed
 	)
 	this.migrationContext.Log.Infof("Issuing and expecting this to block: %s", query)
 	if _, err := tx.Exec(query); err != nil {
-		tablesRenamed <- err
+		if tablesRenamed != nil {
+			tablesRenamed <- err
+		}
 		return this.migrationContext.Log.Errore(err)
 	}
-	tablesRenamed <- nil
+	if tablesRenamed != nil {
+		tablesRenamed <- nil
+	}
 	this.migrationContext.Log.Infof("Tables renamed")
 	return nil
 }
 
+// AtomicCutoverRename renames tables for atomic cut over in non lock session
+func (this *Applier) AtomicCutoverRename(sessionIdChan chan int64, tablesRenamed chan<- error) error {
+	return this.atomicCutoverRename(this.db, sessionIdChan, tablesRenamed)
+}
+
+// AtomicCutoverRenameWithLock renames tables for atomic cut over in the lock session
+func (this *Applier) AtomicCutoverRenameWithLock() error {
+	return this.atomicCutoverRename(this.singletonDB, nil, nil)
+}
+
 func (this *Applier) ShowStatusVariable(variableName string) (result int64, err error) {
 	query := fmt.Sprintf(`show /* gh-ost */ global status like '%s'`, variableName)
 	if err := this.db.QueryRow(query).Scan(&variableName, &result); err != nil {

go/logic/inspect.go

@@ -56,7 +56,7 @@ func (this *Inspector) InitDBConnections() (err error) {
 	if err := this.validateConnection(); err != nil {
 		return err
 	}
-	if !this.migrationContext.AliyunRDS && !this.migrationContext.GoogleCloudPlatform && !this.migrationContext.AzureMySQL {
+	if !this.migrationContext.AliyunRDS && !this.migrationContext.GoogleCloudPlatform && !this.migrationContext.AzureMySQL && !this.migrationContext.OceanBase {
 		if impliedKey, err := mysql.GetInstanceKey(this.db); err != nil {
 			return err
 		} else {

go/logic/migrator.go

@@ -200,6 +200,11 @@ func (this *Migrator) canStopStreaming() bool {
 
 // onChangelogEvent is called when a binlog event operation on the changelog table is intercepted.
 func (this *Migrator) onChangelogEvent(dmlEvent *binlog.BinlogDMLEvent) (err error) {
+	if dmlEvent.NewColumnValues == nil {
+		// in some compatible systems, such as OceanBase Binlog Service, an UPSERT event is
+		// converted to a DELETE event and an INSERT event, we need to skip the DELETE event.
+		return nil
+	}
 	// Hey, I created the changelog table, I know the type of columns it has!
 	switch hint := dmlEvent.NewColumnValues.StringColumn(2); hint {
 	case "state":
@@ -562,9 +567,15 @@ func (this *Migrator) cutOver() (err error) {
 
 	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()
+		if this.migrationContext.OceanBase || !mysql.IsSmallerMinorVersion(this.migrationContext.ApplierMySQLVersion, "8.0.13") {
+			// Atomic solution for latest MySQL: cut over the tables in the same session where the origin
+			// table and ghost table are both locked, it can only work on MySQL 8.0.13 or later versions
+			err = this.atomicCutOverMySQL8()
+		} else {
+			// 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()
+		}
 	case base.CutOverTwoStep:
 		err = this.cutOverTwoStep()
 	default:
@@ -643,6 +654,39 @@ func (this *Migrator) cutOverTwoStep() (err error) {
 	return nil
 }
 
+// atomicCutOverMySQL8 will lock down the original table and the ghost table, execute
+// what's left of last DML entries, and atomically swap original->old, then new->original.
+// It requires to execute RENAME TABLE when the table is LOCKED under WRITE LOCK, which is
+// supported from MySQL 8.0.13, see https://dev.mysql.com/doc/relnotes/mysql/8.0/en/news-8-0-13.html.
+func (this *Migrator) atomicCutOverMySQL8() (err error) {
+	atomic.StoreInt64(&this.migrationContext.InCutOverCriticalSectionFlag, 1)
+	defer atomic.StoreInt64(&this.migrationContext.InCutOverCriticalSectionFlag, 0)
+	atomic.StoreInt64(&this.migrationContext.AllEventsUpToLockProcessedInjectedFlag, 0)
+
+	if err := this.retryOperation(this.applier.LockOriginalTable); err != nil {
+		return err
+	}
+
+	if err := this.retryOperation(this.waitForEventsUpToLock); err != nil {
+		return err
+	}
+	if err := this.retryOperation(this.applier.LockGhostTable); err != nil {
+		return err
+	}
+
+	if err := this.applier.AtomicCutoverRenameWithLock(); err != nil {
+		return err
+	}
+	if err := this.retryOperation(this.applier.UnlockTables); err != nil {
+		return err
+	}
+
+	lockAndRenameDuration := this.migrationContext.RenameTablesEndTime.Sub(this.migrationContext.LockTablesStartTime)
+	renameDuration := this.migrationContext.RenameTablesEndTime.Sub(this.migrationContext.RenameTablesStartTime)
+	this.migrationContext.Log.Debugf("Lock & rename duration: %s (rename only: %s). During this time, queries on %s were locked or failing", lockAndRenameDuration, renameDuration, sql.EscapeName(this.migrationContext.OriginalTableName))
+	return nil
+}
+
 // atomicCutOver
 func (this *Migrator) atomicCutOver() (err error) {
 	atomic.StoreInt64(&this.migrationContext.InCutOverCriticalSectionFlag, 1)

go/mysql/utils.go

@@ -8,6 +8,7 @@ package mysql
 import (
 	gosql "database/sql"
 	"fmt"
+	"strconv"
 	"strings"
 	"sync"
 	"time"
@@ -211,3 +212,47 @@ func Kill(db *gosql.DB, connectionID string) error {
 	_, err := db.Exec(`KILL QUERY %s`, connectionID)
 	return err
 }
+
+func versionTokens(version string, digits int) []int {
+	v := strings.Split(version, "-")[0]
+	tokens := strings.Split(v, ".")
+	intTokens := make([]int, digits)
+	for i := range tokens {
+		if i >= digits {
+			break
+		}
+		intTokens[i], _ = strconv.Atoi(tokens[i])
+	}
+	return intTokens
+}
+
+func isSmallerVersion(version string, otherVersion string, digits int) bool {
+	v := versionTokens(version, digits)
+	o := versionTokens(otherVersion, digits)
+	for i := 0; i < len(v); i++ {
+		if v[i] < o[i] {
+			return true
+		}
+		if v[i] > o[i] {
+			return false
+		}
+		if i == digits {
+			break
+		}
+	}
+	return false
+}
+
+// IsSmallerMajorVersion tests two versions against another and returns true if
+// the former is a smaller "major" version than the latter.
+// e.g. 5.5.36 is NOT a smaller major version as compared to 5.5.40, but IS as compared to 5.6.9
+func IsSmallerMajorVersion(version string, otherVersion string) bool {
+	return isSmallerVersion(version, otherVersion, 2)
+}
+
+// IsSmallerMinorVersion tests two versions against another and returns true if
+// the former is a smaller "minor" version than the latter.
+// e.g. 5.5.36 is a smaller major version as compared to 5.5.40, as well as compared to 5.6.7
+func IsSmallerMinorVersion(version string, otherVersion string) bool {
+	return isSmallerVersion(version, otherVersion, 3)
+}