Reject stream executions if not executed within transaction

2016-12-13 09:40:39.159  WARN 51004 --- [pool-2-thread-1] o.h.engine.jdbc.spi.SqlExceptionHelper   : SQL Error: 0, SQLState: null
2016-12-13 09:40:39.159 ERROR 51004 --- [pool-2-thread-1] o.h.engine.jdbc.spi.SqlExceptionHelper   : [pool-2-thread-1] Timeout: Pool empty. Unable to fetch a connection in 2 seconds, none available[size:200; busy:200; idle:0; lastwait:2000].

public interface PushNotificationRepository extends JpaRepository<PushNotification, Long> {
    @Query(value = "select p from PushNotification p")
    Stream<PushNotification> findAllAndStream();
}

@Service
@Transactional()
public class PushNotificationFlusherService {
    private static final Logger LOGGER = LoggerFactory.getLogger(PushNotificationFlusherService.class);

    private final PushNotificationRepository pushNotificationRepository;

    @Autowired
    public PushNotificationFlusherService(PushNotificationRepository pushNotificationRepository) {
        this.pushNotificationRepository = pushNotificationRepository;
    }

    @Scheduled(fixedDelay = 5000)
    protected void flushPushNotificationQueue() {
        LOGGER.info("Flushing push notifications");

        try (Stream<PushNotification> pushNotifications = pushNotificationRepository.findAllAndStream()) {
            pushNotifications.forEach((PushNotification pushNotification) -> {
               // Send notification 
            });
        }

        LOGGER.info("Flushed push notifications");
    }