Merge pull request #15 from openark/limit-mysql-connetions

All MySQL DBs limited to max 3 concurrent/idle connections

go/base/utils.go

@@ -13,6 +13,7 @@ import (
 	"time"
 
 	gosql "database/sql"
+
 	"github.com/github/gh-ost/go/mysql"
 )
 
@@ -62,7 +63,7 @@ func StringContainsAll(s string, substrings ...string) bool {
 	return nonEmptyStringsFound
 }
 
-func ValidateConnection(db *gosql.DB, connectionConfig *mysql.ConnectionConfig, migrationContext *MigrationContext) (string, error) {
+func ValidateConnection(db *gosql.DB, connectionConfig *mysql.ConnectionConfig, migrationContext *MigrationContext, name string) (string, error) {
 	versionQuery := `select @@global.version`
 	var port, extraPort int
 	var version string
@@ -86,7 +87,7 @@ func ValidateConnection(db *gosql.DB, connectionConfig *mysql.ConnectionConfig,
 	}
 
 	if connectionConfig.Key.Port == port || (extraPort > 0 && connectionConfig.Key.Port == extraPort) {
-		migrationContext.Log.Infof("connection validated on %+v", connectionConfig.Key)
+		migrationContext.Log.Infof("%s connection validated on %+v", name, connectionConfig.Key)
 		return version, nil
 	} else if extraPort == 0 {
 		return "", fmt.Errorf("Unexpected database port reported: %+v", port)

go/logic/applier.go

@@ -57,6 +57,7 @@ type Applier struct {
 	singletonDB       *gosql.DB
 	migrationContext  *base.MigrationContext
 	finishedMigrating int64
+	name              string
 }
 
 func NewApplier(migrationContext *base.MigrationContext) *Applier {
@@ -64,6 +65,7 @@ func NewApplier(migrationContext *base.MigrationContext) *Applier {
 		connectionConfig:  migrationContext.ApplierConnectionConfig,
 		migrationContext:  migrationContext,
 		finishedMigrating: 0,
+		name:              "applier",
 	}
 }
 
@@ -78,11 +80,11 @@ func (this *Applier) InitDBConnections() (err error) {
 		return err
 	}
 	this.singletonDB.SetMaxOpenConns(1)
-	version, err := base.ValidateConnection(this.db, this.connectionConfig, this.migrationContext)
+	version, err := base.ValidateConnection(this.db, this.connectionConfig, this.migrationContext, this.name)
 	if err != nil {
 		return err
 	}
-	if _, err := base.ValidateConnection(this.singletonDB, this.connectionConfig, this.migrationContext); err != nil {
+	if _, err := base.ValidateConnection(this.singletonDB, this.connectionConfig, this.migrationContext, this.name); err != nil {
 		return err
 	}
 	this.migrationContext.ApplierMySQLVersion = version

go/logic/inspect.go

@@ -29,12 +29,14 @@ type Inspector struct {
 	db                  *gosql.DB
 	informationSchemaDb *gosql.DB
 	migrationContext    *base.MigrationContext
+	name                string
 }
 
 func NewInspector(migrationContext *base.MigrationContext) *Inspector {
 	return &Inspector{
 		connectionConfig: migrationContext.InspectorConnectionConfig,
 		migrationContext: migrationContext,
+		name:             "inspector",
 	}
 }
 
@@ -206,7 +208,7 @@ func (this *Inspector) validateConnection() error {
 		return fmt.Errorf("MySQL replication length limited to 32 characters. See https://dev.mysql.com/doc/refman/5.7/en/assigning-passwords.html")
 	}
 
-	version, err := base.ValidateConnection(this.db, this.connectionConfig, this.migrationContext)
+	version, err := base.ValidateConnection(this.db, this.connectionConfig, this.migrationContext, this.name)
 	this.migrationContext.InspectorMySQLVersion = version
 	return err
 }

go/logic/streamer.go

@@ -42,6 +42,7 @@ type EventsStreamer struct {
 	listenersMutex           *sync.Mutex
 	eventsChannel            chan *binlog.BinlogEntry
 	binlogReader             *binlog.GoMySQLReader
+	name                     string
 }
 
 func NewEventsStreamer(migrationContext *base.MigrationContext) *EventsStreamer {
@@ -51,6 +52,7 @@ func NewEventsStreamer(migrationContext *base.MigrationContext) *EventsStreamer
 		listeners:        [](*BinlogEventListener){},
 		listenersMutex:   &sync.Mutex{},
 		eventsChannel:    make(chan *binlog.BinlogEntry, EventsChannelBufferSize),
+		name:             "streamer",
 	}
 }
 
@@ -106,7 +108,7 @@ func (this *EventsStreamer) InitDBConnections() (err error) {
 	if this.db, _, err = mysql.GetDB(this.migrationContext.Uuid, EventsStreamerUri); err != nil {
 		return err
 	}
-	if _, err := base.ValidateConnection(this.db, this.connectionConfig, this.migrationContext); err != nil {
+	if _, err := base.ValidateConnection(this.db, this.connectionConfig, this.migrationContext, this.name); err != nil {
 		return err
 	}
 	if err := this.readCurrentBinlogCoordinates(); err != nil {

go/logic/throttler.go

@@ -188,9 +188,12 @@ func (this *Throttler) collectControlReplicasLag() {
 		dbUri := connectionConfig.GetDBUri("information_schema")
 
 		var heartbeatValue string
-		if db, _, err := mysql.GetDB(this.migrationContext.Uuid, dbUri); err != nil {
+		db, _, err := mysql.GetDB(this.migrationContext.Uuid, dbUri)
+		if err != nil {
 			return lag, err
-		} else if err = db.QueryRow(replicationLagQuery).Scan(&heartbeatValue); err != nil {
+		}
+
+		if err := db.QueryRow(replicationLagQuery).Scan(&heartbeatValue); err != nil {
 			return lag, err
 		}
 

go/mysql/utils.go

@@ -18,8 +18,11 @@ import (
 	"github.com/outbrain/golib/sqlutils"
 )
 
-const MaxTableNameLength = 64
+const (
-const MaxReplicationPasswordLength = 32
+	MaxTableNameLength           = 64
+	MaxReplicationPasswordLength = 32
+	MaxDBPoolConnections         = 3
+)
 
 type ReplicationLagResult struct {
 	Key InstanceKey
@@ -39,23 +42,22 @@ func (this *ReplicationLagResult) HasLag() bool {
 var knownDBs map[string]*gosql.DB = make(map[string]*gosql.DB)
 var knownDBsMutex = &sync.Mutex{}
 
-func GetDB(migrationUuid string, mysql_uri string) (*gosql.DB, bool, error) {
+func GetDB(migrationUuid string, mysql_uri string) (db *gosql.DB, exists bool, err error) {
 	cacheKey := migrationUuid + ":" + mysql_uri
 
 	knownDBsMutex.Lock()
-	defer func() {
+	defer knownDBsMutex.Unlock()
-		knownDBsMutex.Unlock()
-	}()
 
-	var exists bool
+	if db, exists = knownDBs[cacheKey]; !exists {
-	if _, exists = knownDBs[cacheKey]; !exists {
+		db, err = gosql.Open("mysql", mysql_uri)
-		if db, err := gosql.Open("mysql", mysql_uri); err == nil {
+		if err != nil {
+			return nil, false, err
+		}
+		db.SetMaxOpenConns(MaxDBPoolConnections)
+		db.SetMaxIdleConns(MaxDBPoolConnections)
 		knownDBs[cacheKey] = db
-		} else {
-			return db, exists, err
 	}
-	}
+	return db, exists, nil
-	return knownDBs[cacheKey], exists, nil
 }
 
 // GetReplicationLagFromSlaveStatus returns replication lag for a given db; via SHOW SLAVE STATUS