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https://issues.apache.org/jira/browse/DERBY-5894?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13528857#comment-13528857
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Knut Anders Hatlen commented on DERBY-5894:
-------------------------------------------
Synchronizing backupContainer() might fix this particular NPE, but it made some
tests trip over an assert in RAFContainer4.readPage(long,byte[],long). The
problem is that readPage() checks whether the call is synchronized, and behaves
differently if it is. And backupContainer() will end up calling readPage(), but
now synchronized instead of unsynchronized, and this was unexpected. See the
description of "stealth mode" in DERBY-4741 for details.
Synchronization in backupContainer() is only needed in order to protect the
actionCode, actionContainerHandle and actionBackupLocation variables, and those
variables are only needed because all of RAFContainer's privileged operations
share one run() method, I think it's just as reasonable to keep it
unsynchronized and instead let backupContainer() have its own run() method in
an inner class. I even think that it's a cleaner approach in general, both
because it avoids this class of bugs, and because it's more scalable as it
avoids a global lock on the container for each privileged operation (not that
relevant for backup, though, but still...).
The tests that failed when RAFContainer.backupContainer() was made
synchronized, were:
lang.DatabaseClassLoadingTest
lang.TruncateTableAndOnlineBackupTest
derbyall/storeall/storeall.fail:store/rollForwardBackup.sql
derbyall/storeall/storeall.fail:store/rollForwardRecovery.sql
derbyall/storeall/storeall.fail:store/backupRestore.sql
derbyall/storeall/storeall.fail:store/backupRestore1.java
derbyall/storeall/storeall.fail:store/OnlineBackupTest1.java
derbyall/storeall/storeall.fail:store/OnlineBackupTest3.java
derbyall/storeall/storeall.fail:storetests/st_1.sql
derbyall/encryptionAll/encryptionAll.fail:store/encryptDatabaseTest3.sql
> NPE in OnlineBackupTest1 while backing up in stubFileToRemoveAfterCheckPoint
> ----------------------------------------------------------------------------
>
> Key: DERBY-5894
> URL: https://issues.apache.org/jira/browse/DERBY-5894
> Project: Derby
> Issue Type: Bug
> Components: Store
> Reporter: Dag H. Wanvik
> Assignee: Knut Anders Hatlen
> Labels: derby_triage10_10
> Attachments: d5894.zip
>
>
> Saw this while running OnlineBackupTest1 trying to repro DERBY-973.
> ERROR 38000: The exception 'java.lang.NullPointerException' was thrown while
> evaluating an expression.
> at
> org.apache.derby.iapi.error.StandardException.newException(StandardException.java:288)
> at
> org.apache.derby.iapi.error.StandardException.unexpectedUserException(StandardException.java:575)
> at
> org.apache.derby.impl.services.reflect.ReflectMethod.invoke(ReflectMethod.java:63)
> at
> org.apache.derby.impl.sql.execute.CallStatementResultSet.open(CallStatementResultSet.java:75)
> at
> org.apache.derby.impl.sql.GenericPreparedStatement.executeStmt(GenericPreparedStatement.java:443)
> at
> org.apache.derby.impl.sql.GenericPreparedStatement.execute(GenericPreparedStatement.java:324)
> at
> org.apache.derby.impl.jdbc.EmbedStatement.executeStatement(EmbedStatement.java:1242)
> at
> org.apache.derby.impl.jdbc.EmbedPreparedStatement.executeStatement(EmbedPreparedStatement.java:1715)
> at
> org.apache.derby.impl.jdbc.EmbedCallableStatement.executeStatement(EmbedCallableStatement.java:118)
> at
> org.apache.derby.impl.jdbc.EmbedPreparedStatement.execute(EmbedPreparedStatement.java:1370)
> at
> org.apache.derbyTesting.functionTests.tests.store.OnlineBackup.performBackup(OnlineBackup.java:89)
> at
> org.apache.derbyTesting.functionTests.tests.store.OnlineBackup.run(OnlineBackup.java:60)
> at java.lang.Thread.run(Thread.java:637)
> Caused by: java.lang.NullPointerException
> at java.util.Hashtable.put(Hashtable.java:401)
> at
> org.apache.derby.impl.store.raw.data.BaseDataFileFactory.stubFileToRemoveAfterCheckPoint(BaseDataFileFactory.java:1613)
> at
> org.apache.derby.impl.store.raw.data.RAFContainer.run(RAFContainer.java:1651)
> at java.security.AccessController.doPrivileged(Native Method)
> at
> org.apache.derby.impl.store.raw.data.RAFContainer.backupContainer(RAFContainer.java:983)
> at
> org.apache.derby.impl.store.raw.data.BaseContainerHandle.backupContainer(BaseContainerHandle.java:1031)
> at
> org.apache.derby.impl.store.raw.data.BaseDataFileFactory.backupDataFiles(BaseDataFileFactory.java:2466)
> at org.apache.derby.impl.store.raw.RawStore.backup(RawStore.java:978)
> at org.apache.derby.impl.store.raw.RawStore.backup(RawStore.java:649)
> at
> org.apache.derby.impl.store.access.RAMAccessManager.backup(RAMAccessManager.java:964)
> at
> org.apache.derby.impl.db.BasicDatabase.backup(BasicDatabase.java:430)
> at
> org.apache.derby.catalog.SystemProcedures.SYSCS_BACKUP_DATABASE(SystemProcedures.java:961)
> at
> org.apache.derby.exe.acf33d40c7x0138x6d7cx6df3x0000720ad17b0.g0(Unknown
> Source)
> at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
> at
> sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
> at
> sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
> at java.lang.reflect.Method.invoke(Method.java:592)
> at
> org.apache.derby.impl.services.reflect.ReflectMethod.invoke(ReflectMethod.java:46)
> ... 10 more
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