1
我遇到了一个问题追逐“EclipseLink-4005（..）DatabaseAccessor未连接”错误在我们的应用程序的罪魁祸首。它是一个独立的应用程序（不是Web应用程序），具有多个线程连接到相同的数据库（Oracle）。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。该应用程序大多数时间工作正常，但偶尔在高负载下失败，“EclipseLink-4005（..）DatabaseAccessor未连接”错误。DatabaseAccessor未在高负载情况下连接
我能够在我们的测试环境中重现错误，但无法理解可能发生的情况。一些交易长期运行。是否有可能超时，导致相应的会话注销并导致另一个线程中的错误？
下面是样本堆栈跟踪：
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)
(..)
请让我知道如果你需要任何更多的信息。我很高兴分享它，因为我目前没有想法。
启用EclipseLink日志记录后的详细信息。
在日志中，我发现连接在发生错误之前不久就会断开连接（请参见下文）。我的第一个想法是，这是因为它被标记为无效（DatabaseAccessor.setIsValid），但在错误发生之前发生的唯一问题是在30分钟之前抛出OptimisticLockException，并且它由应用程序正常处理。而且，在接下来的半小时内，同样的连接会很愉快地使用，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)
(..)
是否有任何其他原因为什么它可以断开连接？
既然你可以重现它在测试环境中，尝试开启日志记录，看看发生了什么导致到错误。日志记录可能会减慢速度，所以如果它是一个时间问题，可能会更难以重现，但会给你每个确切的场景。另一个要尝试的将是最新的EclipseLink版本，因为涉及堆栈跟踪的类自2.4.2以来有所改变。 – Chris
谢谢@Chris，我启用了日志建议。为问题添加更多信息。 – zaza