MM-24310: Recycle DB connections properly (#14378)

Automatic Merge

store/sqlstore/supplier.go

@@ -426,7 +426,7 @@ func (ss *SqlSupplier) DoesTableExist(tableName string) bool {
 
 	} else if ss.DriverName() == model.DATABASE_DRIVER_SQLITE {
 		count, err := ss.GetMaster().SelectInt(
-			`SELECT name FROM sqlite_master WHERE type='table' AND name=?`,
+			`SELECT count(name) FROM sqlite_master WHERE type='table' AND name=?`,
 			tableName,
 		)
 
@@ -1004,6 +1004,23 @@ func (ss *SqlSupplier) GetAllConns() []*gorp.DbMap {
 	return all
 }
 
+// RecycleDBConnections closes active connections by setting the max conn lifetime
+// to d, and then resets them back to their original duration.
+func (ss *SqlSupplier) RecycleDBConnections(d time.Duration) {
+	// Get old time.
+	originalDuration := time.Duration(*ss.settings.ConnMaxLifetimeMilliseconds) * time.Millisecond
+	// Set the max lifetimes for all connections.
+	for _, conn := range ss.GetAllConns() {
+		conn.Db.SetConnMaxLifetime(d)
+	}
+	// Wait for that period with an additional 2 seconds of scheduling delay.
+	time.Sleep(d + 2*time.Second)
+	// Reset max lifetime back to original value.
+	for _, conn := range ss.GetAllConns() {
+		conn.Db.SetConnMaxLifetime(originalDuration)
+	}
+}
+
 func (ss *SqlSupplier) Close() {
 	ss.master.Db.Close()
 	for _, replica := range ss.replicas {