Ensure cleanup happens, even on error

go/logic/applier.go

@@ -290,12 +290,6 @@ func (this *Applier) WriteChangelogState(value string) (string, error) {
 	return this.WriteAndLogChangelog("state", value)
 }
 
-func (this *Applier) FinalCleanup() {
-	this.db.Close()
-	this.singletonDB.Close()
-	this.finishedMigrating = true
-}
-
 // InitiateHeartbeat creates a heartbeat cycle, writing to the changelog table.
 // This is done asynchronously
 func (this *Applier) InitiateHeartbeat() {
@@ -1044,3 +1038,10 @@ func (this *Applier) ApplyDMLEventQueries(dmlEvents [](*binlog.BinlogDMLEvent))
 	log.Debugf("ApplyDMLEventQueries() applied %d events in one transaction", len(dmlEvents))
 	return nil
 }
+
+func (this *Applier) Teardown() {
+	log.Debugf("Tearing down...")
+	this.db.Close()
+	this.singletonDB.Close()
+	this.finishedMigrating = true
+}

go/logic/inspect.go

@@ -723,3 +723,8 @@ func (this *Inspector) getReplicationLag() (replicationLag time.Duration, err er
 	)
 	return replicationLag, err
 }
+
+func (this *Inspector) Teardown() {
+	this.db.Close()
+	return
+}

go/logic/migrator.go

@@ -291,6 +291,11 @@ func (this *Migrator) Migrate() (err error) {
 	if err := this.validateStatement(); err != nil {
 		return err
 	}
+
+	// After this point, we'll need to teardown anything that's been started
+	//   so we don't leave things hanging around
+	defer this.teardown()
+
 	if err := this.initiateInspector(); err != nil {
 		return err
 	}
@@ -1223,10 +1228,26 @@ func (this *Migrator) finalCleanup() error {
 		}
 	}
 
-	this.finishedMigrating = true
-	this.applier.FinalCleanup()
-	this.eventsStreamer.FinalCleanup()
-	sqlutils.ResetDBCache()
-
 	return nil
 }
+
+func (this *Migrator) teardown() {
+	this.finishedMigrating = true
+
+	if this.inspector != nil {
+		log.Infof("Tearing down inspector")
+		this.inspector.Teardown()
+	}
+
+	if this.applier != nil {
+		log.Infof("Tearing down applier")
+		this.applier.Teardown()
+	}
+
+	if this.eventsStreamer != nil {
+		log.Infof("Tearing down streamer")
+		this.eventsStreamer.Teardown()
+	}
+
+	sqlutils.ResetDBCache()
+}

go/logic/streamer.go

@@ -231,7 +231,7 @@ func (this *EventsStreamer) Close() (err error) {
 	return err
 }
 
-func (this *EventsStreamer) FinalCleanup() {
+func (this *EventsStreamer) Teardown() {
 	this.db.Close()
 	return
 }

go/logic/throttler.go

@@ -187,6 +187,7 @@ func (this *Throttler) collectControlReplicasLag() {
 		} else if err = db.QueryRow(replicationLagQuery).Scan(&heartbeatValue); err != nil {
 			return lag, err
 		}
+
 		lag, err = parseChangelogHeartbeat(heartbeatValue)
 		return lag, err
 	}

go/mysql/utils.go

@@ -40,6 +40,7 @@ func GetReplicationLag(connectionConfig *ConnectionConfig) (replicationLag time.
 	if db, _, err = sqlutils.GetDB(dbUri); err != nil {
 		return replicationLag, err
 	}
+	defer db.Close()
 
 	err = sqlutils.QueryRowsMap(db, `show slave status`, func(m sqlutils.RowMap) error {
 		slaveIORunning := m.GetString("Slave_IO_Running")
@@ -52,7 +53,6 @@ func GetReplicationLag(connectionConfig *ConnectionConfig) (replicationLag time.
 		return nil
 	})
 
-	db.Close()
 	return replicationLag, err
 }