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https://issues.apache.org/jira/browse/DBCP-398?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13666376#comment-13666376
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Phil Steitz commented on DBCP-398:
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Thanks, Sarvesh. Looking at the client code, I now understand what is going on.
You are using isClosed() to decide whether or not to close (i.e. return to the
pool) the PoolableConnection. Sorry for being a little slow. I agree that the
isClosed implementation in PoolableConnection is questionable, but it arguably
conforms to the JDBC spec (closed means it can no longer be used to connect to
the database) and I wonder what other client apps might break if we change it.
I am on the fence and would appreciate some more community input on whether or
not we should make this change, which is a basically a change in the contract
for PoolableConnection#isClosed. It could be that it is best to make this
change in 2.0 (which has the same behavior) or via a new method (see below).
Arguably, the client code should not be testing isClosed, but just invoking
close directly. As of 1.3/1.4, close is idempotent, so there is no risk of
exception on multiple close. In any case, once a connection has been returned
to the pool, clients should discard references to it.
What do others think about the proposed changes in behavior:
(1) drop _con.isClosed() test from PoolableConnection#isClosed() (so "closed"
really means "has been returned to the pool")
(2) do not throw when a connection that has been closed without knowledge of
the pool is closed.
One more note on this. If we do decide to make a change, it might be better to
implement it in the PoolGuardConnectionWrapper, possibly even implementing a
new method, isDiscarded() or somesuch to disambiguate isClosed.
> DBCP hangs on common pool borrowObject when PoolableConnection is used and
> the underlying connection closed unexpectedly (connection resets/timouts)
> ----------------------------------------------------------------------------------------------------------------------------------------------------
>
> Key: DBCP-398
> URL: https://issues.apache.org/jira/browse/DBCP-398
> Project: Commons Dbcp
> Issue Type: Bug
> Reporter: Sarvesh Sakalanaga
> Attachments: DBCP-398.0.patch
>
>
> The bug is in org.apache.commons.dbcp.PoolableConnection as isClosed method
> on this calls super.isClosed which returns true (as
> DelegatingConnection::isClosed { _closed || _conn.isClosed() }). Since
> PoolableConnection needs to release objects to pool even if the underlying
> connection is closed the isClosed method should be overridden in this class
> and should return _closed. This _closed is the delegating connection close
> which will be set to false even if the underlying connection is closed
> (_conn.isClosed). The fix should also not throw on PoolableConnection::Close
> method if underlying connection is closed as this state is a valid state and
> is expected.
> Also currently the way it stands the clients of PoolableConnection will/may
> not call Close() as isClosed always returns true in this case.
> Below is the stack that the thread hangs on:
> ◾waiting on <0x00000007b5a50e48> (a
> org.apache.commons.pool.impl.GenericObjectPool$Latch)
> at java.lang.Object.wait(Object.java:503)
> at
> org.apache.commons.pool.impl.GenericObjectPool.borrowObject(GenericObjectPool.java:1104)
> ◾locked <0x00000007b5a50e48> (a
> org.apache.commons.pool.impl.GenericObjectPool$Latch)
> at
> org.apache.commons.dbcp.PoolingDataSource.getConnection(PoolingDataSource.java:106)
> at
> org.datanucleus.store.rdbms.ConnectionProviderPriorityList.getConnection(ConnectionProviderPriorityList.java:57)
> at
> org.datanucleus.store.rdbms.ConnectionFactoryImpl$ManagedConnectionImpl.getConnection(ConnectionFactoryImpl.java:354)
> at
> org.datanucleus.store.rdbms.ConnectionFactoryImpl$ManagedConnectionImpl.getXAResource(ConnectionFactoryImpl.java:314)
> at
> org.datanucleus.store.connection.ConnectionManagerImpl.enlistResource(ConnectionManagerImpl.java:386)
> at
> org.datanucleus.store.connection.ConnectionManagerImpl.allocateConnection(ConnectionManagerImpl.java:252)
> at
> org.datanucleus.store.connection.AbstractConnectionFactory.getConnection(AbstractConnectionFactory.java:60)
> at
> org.datanucleus.store.AbstractStoreManager.getConnection(AbstractStoreManager.java:449)
> at
> org.datanucleus.store.AbstractStoreManager.getConnection(AbstractStoreManager.java:418)
> at
> org.datanucleus.store.rdbms.query.JDOQLQuery.performExecute(JDOQLQuery.java:595)
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