java – Spring无法将事务传播到ForkJoin的RecursiveAction

我正在尝试实现一个多线程解决方案,以便我可以并行化我的业务逻辑,包括读取和写入数据库.

技术堆栈：Spring 4.0.2,Hibernate 4.3.8

以下是一些要讨论的代码：

组态

@Configuration
public class PartitionersConfig {

    @Bean
    public ForkJoinPoolfactorybean forkJoinPoolfactorybean() {
        final ForkJoinPoolfactorybean poolFactory = new ForkJoinPoolfactorybean();
        return poolFactory;
    }
}

服务

@Service
@Transactional
public class MyService {

    @Autowired
    private OtherService otherService;

    @Autowired
    private ForkJoinPool forkJoinPool;

    @Autowired
    private MyDao myDao;

    public void performPartitionedActionOnIds() {
        final ArrayList<UUID> ids = otherService.getIds();

        MyIdPartitioner task = new MyIdsPartitioner(ids,myDao,ids.size() - 1);
        forkJoinPool.invoke(task);
    }
}

存储库/ DAO

@Repository
@Transactional(propagation = Propagation.MANDATORY)
public class IdsDao {

    public MyData getData(List<UUID> list) {
        // ... 
    }
}

RecursiveAction

public class MyIdsPartitioner extends RecursiveAction {

    private static final long serialVersionUID = 1L;
    private static final int THRESHOLD = 100;

    private ArrayList<UUID> ids;
    private int fromIndex;
    private int toIndex;

    private MyDao myDao;

    public MyIdsPartitioner(ArrayList<UUID> ids,MyDao myDao,int fromIndex,int toIndex) {
        this.ids = ids;
        this.fromIndex = fromIndex;
        this.toIndex = toIndex;
        this.myDao = myDao;
    }

    @Override
    protected void compute() {
        if (computationSetIsSamllEnough()) {
            computeDirectly();
        } else {
            int leftToIndex = fromIndex + (toIndex - fromIndex) / 2;
            MyIdsPartitioner leftPartitioner = new MyIdsPartitioner(ids,fromIndex,leftToIndex);
            MyIdsPartitioner rightPartitioner = new MyIdsPartitioner(ids,leftToIndex + 1,toIndex);

            invokeAll(leftPartitioner,rightPartitioner);
        }
    }

    private boolean computationSetIsSamllEnough() {
        return (toIndex - fromIndex) < THRESHOLD;
    }

    private void computeDirectly() {
        final List<UUID> subList = ids.subList(fromIndex,toIndex);
        final MyData myData = myDao.getData(sublist);
        modifyTheData(myData);
    }

    private void modifyTheData(MyData myData) {
        // ...
        // write to DB
    }
}

执行此操作后,我得到：

No existing transaction found for transaction marked with propagation ‘mandatory’

我理解这是完全正常的,因为事务不会通过不同的线程传播.因此,一个解决方案是在每个线程as proposed in another similar question中手动创建一个事务.但这对我来说不够令人满意,所以我一直在搜索.

在Spring的论坛中我找到了a discussion on the topic.我发现一段非常有趣：

“I can imagine one Could manually propagate the transaction context to another thread,but I don’t think you should really try it. Transactions are bound to single threads with a reason – the basic underlying resource – jdbc connection – is not threadsafe. Using one single connection in multiple threads would break fundamental jdbc request/response contracts and it would be a small wonder if it would work in more then trivial examples.”

因此,第一个问题出现了：是否值得对数据库的读/写进行简化,这是否真的会损害数据库的一致性？
如果上面的引用不正确,我怀疑,有没有办法实现以下目的：
MyIdPartitioner将被Spring管理 – 使用@Scope(“prototype”) – 并传递所需的参数以进行递归调用,这样就可以将事务管理留给Spring了吗？

解决方法

这应该可以使用atomikos( http://www.atomikos.com)并可选择使用嵌套事务.

如果这样做,那么如果同一根事务的多个线程写入数据库中的相同表,请注意避免死锁.

原文地址：https://www.jb51.cc/java/129185.html