Aliyun RDS hide some mysql variables for secrity so gh-ost will get

ilegal values. Add --aliyun-rds flag to avoid getting them.

go/base/context.go

@@ -91,6 +91,7 @@ type MigrationContext struct {
 	SkipRenamedColumns       bool
 	IsTungsten               bool
 	DiscardForeignKeys       bool
+	AliyunRDS                bool
 
 	config            ContextConfig
 	configMutex       *sync.Mutex
@@ -214,6 +215,8 @@ type ContextConfig struct {
 	}
 }
 
+var Context *MigrationContext
+
 func NewMigrationContext() *MigrationContext {
 	return &MigrationContext{
 		Uuid:                                uuid.NewV4().String(),

go/base/utils.go

@@ -65,16 +65,25 @@ func StringContainsAll(s string, substrings ...string) bool {
 }
 
 func ValidateConnection(db *gosql.DB, connectionConfig *mysql.ConnectionConfig) (string, error) {
-	query := `select @@global.port, @@global.version`
+	versionQuery := `select @@global.version`
 	var port, extraPort int
 	var version string
-	if err := db.QueryRow(query).Scan(&port, &version); err != nil {
+	if err := db.QueryRow(versionQuery).Scan(&version); err != nil {
 		return "", err
 	}
 	extraPortQuery := `select @@global.extra_port`
 	if err := db.QueryRow(extraPortQuery).Scan(&extraPort); err != nil {
 		// swallow this error. not all servers support extra_port
 	}
+	// AliyunRDS set users port to "NULL", replace it by gh-ost param
+	if Context.AliyunRDS {
+		port = connectionConfig.Key.Port
+	} else {
+		portQuery := `select @@global.port`
+		if err := db.QueryRow(portQuery).Scan(&port); err != nil {
+			return "", err
+		}
+	}
 
 	if connectionConfig.Key.Port == port || (extraPort > 0 && connectionConfig.Key.Port == extraPort) {
 		log.Infof("connection validated on %+v", connectionConfig.Key)

go/cmd/gh-ost/main.go

@@ -44,6 +44,7 @@ func acceptSignals(migrationContext *base.MigrationContext) {
 // main is the application's entry point. It will either spawn a CLI or HTTP interfaces.
 func main() {
 	migrationContext := base.NewMigrationContext()
+	base.Context = migrationContext
 
 	flag.StringVar(&migrationContext.InspectorConnectionConfig.Key.Hostname, "host", "127.0.0.1", "MySQL hostname (preferably a replica, not the master)")
 	flag.StringVar(&migrationContext.AssumeMasterHostname, "assume-master-host", "", "(optional) explicitly tell gh-ost the identity of the master. Format: some.host.com[:port] This is useful in master-master setups where you wish to pick an explicit master, or in a tungsten-replicator where gh-ost is unable to determine the master")
@@ -68,6 +69,7 @@ func main() {
 	flag.BoolVar(&migrationContext.IsTungsten, "tungsten", false, "explicitly let gh-ost know that you are running on a tungsten-replication based topology (you are likely to also provide --assume-master-host)")
 	flag.BoolVar(&migrationContext.DiscardForeignKeys, "discard-foreign-keys", false, "DANGER! This flag will migrate a table that has foreign keys and will NOT create foreign keys on the ghost table, thus your altered table will have NO foreign keys. This is useful for intentional dropping of foreign keys")
 	flag.BoolVar(&migrationContext.SkipForeignKeyChecks, "skip-foreign-key-checks", false, "set to 'true' when you know for certain there are no foreign keys on your table, and wish to skip the time it takes for gh-ost to verify that")
+	flag.BoolVar(&migrationContext.AliyunRDS, "aliyun-rds", false, "set to 'true' when you execute on Aliyun RDS.")
 
 	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

@@ -89,10 +89,12 @@ func (this *Applier) InitDBConnections() (err error) {
 	if err := this.validateAndReadTimeZone(); err != nil {
 		return err
 	}
-	if impliedKey, err := mysql.GetInstanceKey(this.db); err != nil {
+	if impliedKey, err := mysql.GetInstanceKey(this.db, this.migrationContext.AliyunRDS); err != nil {
 		return err
 	} else {
-		this.connectionConfig.ImpliedKey = impliedKey
+		if this.migrationContext.AliyunRDS != true {
+			this.connectionConfig.ImpliedKey = impliedKey
+		}
 	}
 	if err := this.readTableColumns(); err != nil {
 		return err

go/logic/inspect.go

@@ -53,10 +53,12 @@ func (this *Inspector) InitDBConnections() (err error) {
 	if err := this.validateConnection(); err != nil {
 		return err
 	}
-	if impliedKey, err := mysql.GetInstanceKey(this.db); err != nil {
+	if impliedKey, err := mysql.GetInstanceKey(this.db, this.migrationContext.AliyunRDS); err != nil {
 		return err
 	} else {
-		this.connectionConfig.ImpliedKey = impliedKey
+		if this.migrationContext.AliyunRDS != true {
+			this.connectionConfig.ImpliedKey = impliedKey
+		}
 	}
 	if err := this.validateGrants(); err != nil {
 		return err

go/mysql/utils.go

@@ -171,9 +171,11 @@ func GetSelfBinlogCoordinates(db *gosql.DB) (selfBinlogCoordinates *BinlogCoordi
 }
 
 // GetInstanceKey reads hostname and port on given DB
-func GetInstanceKey(db *gosql.DB) (instanceKey *InstanceKey, err error) {
+func GetInstanceKey(db *gosql.DB, isAliyunRDS bool) (instanceKey *InstanceKey, err error) {
 	instanceKey = &InstanceKey{}
-	err = db.QueryRow(`select @@global.hostname, @@global.port`).Scan(&instanceKey.Hostname, &instanceKey.Port)
+	if isAliyunRDS != true {
+		err = db.QueryRow(`select @@global.hostname, @@global.port`).Scan(&instanceKey.Hostname, &instanceKey.Port)
+	}
 	return instanceKey, err
 }