Question

我的应用程序（java spring-core）有几个并发运行的线程并访问db，我在某个高峰时间遇到异常

07:43:33,400 WARN  [org.hibernate.util.JDBCExceptionReporter] SQL Error: 1213, SQLState: 40001
07:43:33,808 ERROR [org.hibernate.util.JDBCExceptionReporter] Deadlock found when trying to get lock; try restarting transaction
07:43:33,808 ERROR [org.hibernate.event.def.AbstractFlushingEventListener] Could not synchronize database state with session
org.hibernate.exception.LockAcquisitionException: could not insert: [com.xminds.bestfriend.frontend.model.Question]
    at org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:107)
    at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:66)
    at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:2436)
    at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:2856)
    at org.hibernate.action.EntityInsertAction.execute(EntityInsertAction.java:79)
    at org.hibernate.engine.ActionQueue.execute(ActionQueue.java:273)
    at org.hibernate.engine.ActionQueue.executeActions(ActionQueue.java:265)
    at org.hibernate.engine.ActionQueue.executeActions(ActionQueue.java:184)
    at org.hibernate.event.def.AbstractFlushingEventListener.performExecutions(AbstractFlushingEventListener.java:321)
    at org.hibernate.event.def.DefaultFlushEventListener.onFlush(DefaultFlushEventListener.java:51)
    at org.hibernate.impl.SessionImpl.flush(SessionImpl.java:1216)
    at org.hibernate.impl.SessionImpl.managedFlush(SessionImpl.java:383)
    at org.hibernate.transaction.JDBCTransaction.commit(JDBCTransaction.java:133)
    at org.springframework.orm.hibernate3.HibernateTransactionManager.doCommit(HibernateTransactionManager.java:656)
    at org.springframework.transaction.support.AbstractPlatformTransactionManager.processCommit(AbstractPlatformTransactionManager.java:754)
    at org.springframework.transaction.support.AbstractPlatformTransactionManager.commit(AbstractPlatformTransactionManager.java:723)
    at org.springframework.transaction.support.TransactionTemplate.execute(TransactionTemplate.java:147)
    at com.xminds.bestfriend.consumers.Base.onMessage(Base.java:96)
    at org.springframework.jms.listener.adapter.MessageListenerAdapter.onMessage(MessageListenerAdapter.java:339)
    at org.springframework.jms.listener.AbstractMessageListenerContainer.doInvokeListener(AbstractMessageListenerContainer.java:535)
    at org.springframework.jms.listener.AbstractMessageListenerContainer.invokeListener(AbstractMessageListenerContainer.java:495)
    at org.springframework.jms.listener.AbstractMessageListenerContainer.doExecuteListener(AbstractMessageListenerContainer.java:467)
    at org.springframework.jms.listener.AbstractPollingMessageListenerContainer.doReceiveAndExecute(AbstractPollingMessageListenerContainer.java:325)
    at org.springframework.jms.listener.AbstractPollingMessageListenerContainer.receiveAndExecute(AbstractPollingMessageListenerContainer.java:263)
    at org.springframework.jms.listener.DefaultMessageListenerContainer$AsyncMessageListenerInvoker.invokeListener(DefaultMessageListenerContainer.java:1058)
    at org.springframework.jms.listener.DefaultMessageListenerContainer$AsyncMessageListenerInvoker.executeOngoingLoop(DefaultMessageListenerContainer.java:1050)
    at org.springframework.jms.listener.DefaultMessageListenerContainer$AsyncMessageListenerInvoker.run(DefaultMessageListenerContainer.java:947)
    at java.lang.Thread.run(Thread.java:662)
Caused by: com.mysql.jdbc.exceptions.jdbc4.MySQLTransactionRollbackException: Deadlock found when trying to get lock; try restarting transaction
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)
    at com.mysql.jdbc.Util.getInstance(Util.java:386)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1065)
    at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:4074)
    at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:4006)
    at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:2468)
    at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2629)
    at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2719)
    at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:2155)
    at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:2450)
    at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:2371)
    at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:2355)
    at com.mchange.v2.c3p0.impl.NewProxyPreparedStatement.executeUpdate(NewProxyPreparedStatement.java:105)
    at org.hibernate.jdbc.NonBatchingBatcher.addToBatch(NonBatchingBatcher.java:46)
    at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:2416)
    ... 25 more

我的代码看起来

try
{
       this.consumerTransactionTemplate.execute(new TransactionCallbackWithoutResult(){

                    @Override
                    protected void doInTransactionWithoutResult(
                            TransactionStatus status)
                    {
                        process();
                    }

                });

  }
  catch(Exception e){
     logger.error("Exception occured " , e);
      //TODO: Exception handling
  }

Answer 1

MySQL的InnoDB引擎支持行级锁定，即使代码插入或更新单行时也会导致死锁（特别是如果表上有多个索引正在更新）。最好的办法是围绕此设计代码，以便在由于死锁而失败时重试事务。有关MySQL死锁诊断和可能的解决方法的一些有用信息可用here。

可以通过Spring中的AOP进行死锁重试的有趣实现here。这样，您只需要将注释添加到要在死锁情况下重试的方法。

Answer 2

Emir的答案很棒，它描述了你遇到的问题。不过，我建议你试试spring-retry。

它是一个出色的框架，通过注释实现重试模式。

示例：

@Retryable(maxAttempts = 4, backoff = @Backoff(delay = 500)) public void doSomethingWithMysql() { consumerTransactionTemplate.execute( new TransactionCallbackWithoutResult(){ @Override protected void doInTransactionWithoutResult( TransactionStatus status) { process(); } }); }

如果有任何异常，它将重试（调用）方法 doSomethingWithMysql（）最多4次，退避策略为500ms

Answer 3

这是一个使用纯Spring且没有额外框架的示例。

    TransactionTemplate transactionTemplate = new TransactionTemplate(transactionManager); // autowired
    transactionTemplate.setIsolationLevel(TransactionDefinition.ISOLATION_SERIALIZABLE); // this increases deadlocks, but prevents multiple simultaneous similar requests from inserting multiple rows
    Object o = transactionTemplate.execute(txStatus -> {
            for (int i=0; i<3; i++) {
                try {
                    return findExistingOrCreate(...);
                } catch (DeadlockLoserDataAccessException e) {
                    Logger.info(TAG, "create()", "Deadlock exception when trying to find or create. Retrying "+(2-i)+" more times...");
                    try { Thread.sleep(2^i*1000); } catch (InterruptedException e2) {}
                }
            }
            return null;
    });
    if (o == null) throw new ApiException(HttpStatus.SERVICE_UNAVAILABLE, "Possible deadlock or busy database, please try again later.");

使用serializable transaction isolation level特定于我的情况，因为它将SELECT转换为SELECT ... IN SHARE MODE / SELECT ... FOR UPDATE并锁定这些行。 findExistingOrCreate()对现有行进行了大量复杂的搜索，并自动生成名称并检查错误单词等。当同时出现多个相同请求时，它将创建多个行。使用可序列化的事务隔离级别，现在为indempotent；现在，它会锁定行，创建一行，然后所有后续请求都返回新的现有行。

Answer 4

如果您使用的是JPA / Hibernate，则只需执行以下步骤即可避免死锁。一旦获得了锁，就不要在事务中的任何地方对具有相同ID的db进行任何调用（我的意思是说，您不应该再在sameid上获得实体），对您修改的锁对象也没有任何问题。

服务水平：-

employee=empDao.getForUpdate(id);

道级：-

public employee getForUpdate(String id)
return mySqlRepository.getForUpdate(id)

存储库（接口）：-

@Lock(LockModeType.PESSIMITSIC_WRITE)
@Query("select e from employee e where id=?1")
public employee getForUpdate(String id)

Answer 5

当您遇到此类错误时“检测到死锁”。您应检查查询执行情况，并验证两个或多个并发事务是否可能导致死锁。

这些事务应该以相同的顺序获取数据库锁，以避免死锁。

获取“尝试获取锁定时发现死锁;尝试重新启动事务”

5 个答案: