java - 高负载场景下DatabaseAccessor未连接

Question

我在追查应用程序中“EclipseLink-4005 (..) DatabaseAccessor notconnected”错误的罪魁祸首时遇到问题。它是一个独立的应用程序(不是 Web 应用程序)，具有连接到同一数据库(Oracle)的多个线程。我们使用 EclipseLink 2.4.2 及其默认设置的内部连接池。事务在应用程序中进行管理并且可以嵌套。该应用程序在大多数情况下工作正常，但偶尔在高负载下会失败，并出现“EclipseLink-4005 (..) DatabaseAccessor notconnected”错误。

我能够在我们的测试环境中重现该错误，但无法理解在什么条件下可能会发生该错误。有些事务需要长时间运行。是否有可能其中一些超时，导致各自的 session 注销并导致另一个线程中的错误？

下面是示例堆栈跟踪:

Exception [EclipseLink-4005] (Eclipse Persistence Services - 2.4.2.v20130514-5956486): org.eclipse.persistence.exceptions.DatabaseException
Exception Description: DatabaseAccessor not connected.
    at org.eclipse.persistence.exceptions.DatabaseException.databaseAccessorNotConnected(DatabaseException.java:116)
    at org.eclipse.persistence.internal.databaseaccess.DatasourceAccessor.incrementCallCount(DatasourceAccessor.java:309)
    at org.eclipse.persistence.internal.databaseaccess.DatasourceAccessor.beginTransaction(DatasourceAccessor.java:238)
    at org.eclipse.persistence.internal.sessions.AbstractSession.basicBeginTransaction(AbstractSession.java:526)
    at org.eclipse.persistence.sessions.server.ClientSession.addWriteConnection(ClientSession.java:693)
    at org.eclipse.persistence.sessions.server.ServerSession.acquireClientConnection(ServerSession.java:246)
    at org.eclipse.persistence.sessions.server.ClientSession.getAccessor(ClientSession.java:333)
    at org.eclipse.persistence.internal.sessions.UnitOfWorkImpl.getAccessor(UnitOfWorkImpl.java:1867)
    at org.eclipse.persistence.internal.jpa.EntityManagerImpl.unwrap(EntityManagerImpl.java:2540)
    (..)

和

Exception [EclipseLink-4005] (Eclipse Persistence Services - 2.4.2.v20130514-5956486): org.eclipse.persistence.exceptions.DatabaseException
Exception Description: DatabaseAccessor not connected.
    at org.eclipse.persistence.exceptions.DatabaseException.databaseAccessorNotConnected(DatabaseException.java:116)
    at org.eclipse.persistence.internal.databaseaccess.DatasourceAccessor.incrementCallCount(DatasourceAccessor.java:309)
    at org.eclipse.persistence.internal.databaseaccess.DatasourceAccessor.rollbackTransaction(DatasourceAccessor.java:671)
    at org.eclipse.persistence.internal.databaseaccess.DatabaseAccessor.rollbackTransaction(DatabaseAccessor.java:1576)
    at org.eclipse.persistence.internal.sessions.AbstractSession.basicRollbackTransaction(AbstractSession.java:629)
    at org.eclipse.persistence.sessions.server.ClientSession.basicRollbackTransaction(ClientSession.java:186)
    at org.eclipse.persistence.internal.sessions.AbstractSession.rollbackTransaction(AbstractSession.java:3561)
    at org.eclipse.persistence.internal.sessions.UnitOfWorkImpl.rollbackTransaction(UnitOfWorkImpl.java:4641)
    at org.eclipse.persistence.internal.sessions.RepeatableWriteUnitOfWork.rollbackTransaction(RepeatableWriteUnitOfWork.java:522)
    at org.eclipse.persistence.internal.sessions.UnitOfWorkImpl.release(UnitOfWorkImpl.java:4448)
    at org.eclipse.persistence.internal.jpa.transaction.EntityTransactionImpl.rollback(EntityTransactionImpl.java:127)
    (..)

如果您需要更多信息，请告诉我。我很高兴分享它，因为我目前没有想法。

<小时/>

启用 EclipseLink 日志记录后的更多信息。

在日志中，我发现连接在错误发生前不久就断开了(见下文)。我的第一个想法是，这是因为它被标记为无效(使用DatabaseAccessor.setIsValid)，但在错误之前发生的唯一问题是 30 分钟前抛出的 OptimisticLockException，并且应用程序妥善处理了它。此外，在接下来的半小时内，相同的连接很高兴地使用，所以我不认为它被标记为无效。

TRACE  [2017-09-01 10:01:04.851/-0700] [Worker-659:org.eclipse.persistence.transaction] [ ] 2017-09-01 10:01:04.851--ClientSession(436256688)--Connection(148152749)--Thread(Thread[Worker-659,5,main])-- commit transaction
TRACE  [2017-09-01 10:01:04.914/-0700] [Worker-659:org.eclipse.persistence.connection] [ ] 2017-09-01 10:01:04.914--ServerSession(441145695)--Connection(148152749)--Thread(Thread[Worker-659,5,main])-- Connection released to connection pool [default].
DEBUG  [2017-09-01 10:01:04.914/-0700] [Worker-659:org.eclipse.persistence.connection] [ ] 2017-09-01 10:01:04.914--ServerSession(441145695)--Connection(148152749)--Thread(Thread[Worker-659,5,main])-- disconnect
TRACE  [2017-09-01 10:01:04.929/-0700] [Worker-659:org.eclipse.persistence.transaction] [ ] 2017-09-01 10:01:04.929--UnitOfWork(122187888)--Thread(Thread[Worker-659,5,main])-- end unit of work commit
TRACE  [2017-09-01 10:01:04.929/-0700] [Worker-659:org.eclipse.persistence.transaction] [ ] 2017-09-01 10:01:04.929--UnitOfWork(122187888)--Thread(Thread[Worker-659,5,main])-- resume unit of work
TRACE  [2017-09-01 10:01:04.929/-0700] [Worker-659:org.eclipse.persistence.transaction] [ ] 2017-09-01 10:01:04.929--UnitOfWork(122187888)--Thread(Thread[Worker-659,5,main])-- release unit of work
TRACE  [2017-09-01 10:01:04.929/-0700] [Worker-659:org.eclipse.persistence.connection] [ ] 2017-09-01 10:01:04.929--ClientSession(436256688)--Thread(Thread[Worker-659,5,main])-- client released
TRACE  [2017-09-01 10:01:04.929/-0700] [Worker-659:org.eclipse.persistence.query] [ ] 2017-09-01 10:01:04.929--UnitOfWork(122187888)--Thread(Thread[Worker-659,5,main])-- Execute query ReadAllQuery(...)
TRACE  [2017-09-01 10:01:04.929/-0700] [Worker-659:org.eclipse.persistence.connection] [ ] 2017-09-01 10:01:04.929--ServerSession(441145695)--Connection(985262420)--Thread(Thread[Worker-659,5,main])-- Connection acquired from connection pool [default].
TRACE  [2017-09-01 10:01:04.961/-0700] [Worker-659:org.eclipse.persistence.connection] [ ] 2017-09-01 10:01:04.961--ServerSession(441145695)--Connection(985262420)--Thread(Thread[Worker-659,5,main])-- Connection released to connection pool [default].
WARN   [2017-09-01 10:01:04.961/-0700] [Worker-659:org.eclipse.persistence] [ ] 2017-09-01 10:01:04.961--UnitOfWork(122187888)--Thread(Thread[Worker-659,5,main])-- 
Local Exception Stack: 
Exception [EclipseLink-4005] (Eclipse Persistence Services - 2.4.2.v20130514-5956486): org.eclipse.persistence.exceptions.DatabaseException
Exception Description: DatabaseAccessor not connected.
    at org.eclipse.persistence.exceptions.DatabaseException.databaseAccessorNotConnected(DatabaseException.java:116)
    at org.eclipse.persistence.internal.databaseaccess.DatasourceAccessor.incrementCallCount(DatasourceAccessor.java:309)
    at org.eclipse.persistence.internal.databaseaccess.DatabaseAccessor.basicExecuteCall(DatabaseAccessor.java:581)
    at org.eclipse.persistence.internal.databaseaccess.DatabaseAccessor.executeCall(DatabaseAccessor.java:537)
    at org.eclipse.persistence.internal.sessions.AbstractSession.basicExecuteCall(AbstractSession.java:1805)
    at org.eclipse.persistence.sessions.server.ServerSession.executeCall(ServerSession.java:566)
(..)

是否还有其他原因导致其断开连接？

Answer 1

请允许我回答我自己的问题，以便其他人可以从我的发现中受益。

该问题是由 Eclipse Link 中的错误引起的。请参阅bug 432410 ，在撰写本文时仍然开放。

我的特定情况下的解决方案是避免解开连接，即不调用EntityManager.unwrap(Connection.class)