public function getAvailableJobs($queue, $max = 10) {
        $qb = $this->conn->createQueryBuilder();
        $qb->select('*');
        $qb->from($this->table_name);
        $qb->where('status = :status AND queue = :queue AND available_at <= :now');
        $qb->orderBy('status');
        $qb->setParameters([
            'status' => self::JOB_STATUS_CREATED,
            'queue' => $queue,
        ]);
        $qb->setParameter('now', new \DateTime(), Type::DATETIME);
        $qb->setMaxResults($max);
        $stmt = $qb->execute();
        return $stmt->fetchAll(\PDO::FETCH_ASSOC);
    }