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我遇到了一個問題追逐「EclipseLink-4005（..）DatabaseAccessor未連接」錯誤在我們的應用程序的罪魁禍首。它是一個獨立的應用程序（不是Web應用程序），具有多個線程連接到相同的數據庫（Oracle）。我們使用EclipseLink 2.4.2及其默認設置的內部連接池。事務在應用程序中進行管理，並且可以嵌套。該應用程序大多數時間工作正常，但偶爾在高負載下失敗，「EclipseLink-4005（..）DatabaseAccessor未連接」錯誤。DatabaseAccessor未在高負載情況下連接
我能夠在我們的測試環境中重現錯誤，但無法理解可能發生的情況。一些交易長期運行。是否有可能超時，導致相應的會話註銷並導致另一個線程中的錯誤？
下面是樣本堆棧跟蹤：
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)
(..)
請讓我知道如果你需要任何更多的信息。我很高興分享它，因爲我目前沒有想法。
啓用EclipseLink日誌記錄後的詳細信息。
在日誌中，我發現連接在發生錯誤之前不久就會斷開連接（請參見下文）。我的第一個想法是，這是因爲它被標記爲無效（DatabaseAccessor.setIsValid），但在錯誤發生之前發生的唯一問題是在30分鐘之前拋出OptimisticLockException，並且它由應用程序正常處理。而且，在接下來的半小時內，同樣的連接會很愉快地使用，所以我不認爲它被標記爲無效。
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爲什麼它可以斷開連接？
既然你可以重現它在測試環境中，嘗試開啓日誌記錄，看看發生了什麼導致到錯誤。日誌記錄可能會減慢速度，所以如果它是一個時間問題，可能會更難以重現，但會給你每個確切的場景。另一個要嘗試的將是最新的EclipseLink版本，因爲涉及堆棧跟蹤的類自2.4.2以來有所改變。 – Chris
謝謝@Chris，我啓用了日誌建議。爲問題添加更多信息。 – zaza