[ http://issues.apache.org/jira/browse/DERBY-1021?page=all ]
Deepa Remesh closed DERBY-1021:
-------------------------------
Fix Version: 10.2.0.0
Resolution: Fixed
This issue has been partly resolved by check-ins for DERBY-1103. A new sub-task
(DERBY-1104) is opened for further work.
> Perform cleanup actions which require synchronization outside the finalizer
> ---------------------------------------------------------------------------
>
> Key: DERBY-1021
> URL: http://issues.apache.org/jira/browse/DERBY-1021
> Project: Derby
> Type: Bug
> Components: Network Client
> Environment: Derby Network Client Driver
> Reporter: Deepa Remesh
> Fix For: 10.2.0.0
>
> In client driver, finalize() method in Statement class involves synchronized
> calls. This may block the finalizer thread and potentially the JVM. In
> general, avoid any synchronized operation from finalizer. Embedded driver
> performs the cleanup actions outside the finalizer. See
> EmbedPreparedStatement.finalize. A similar mechanism needs to be used in
> client driver.
> The existing code in client's finalize() methods do not cause any problems so
> far because finalize was getting called only after explicit close of
> statement objects. So the code in the finalizer does not get exercised. Once
> the memory leaks are removed as part of DERBY-210
> (https://issues.apache.org/jira/browse/DERBY-210), the finalizer can get
> called as soon as the application dereferences a statement object.
> To be able to proceed with DERBY-210, patch4 in DERBY-210 changes the
> finalizer method to not do any synchronized actions. It removes sending of
> any network messages from finalizer:
> 1) Removes sending commit messages to network server
> 2) Removes sending CLSQRY to cleanup all result sets of a statement on
> network server since the cleanup of result sets on network server will happen
> when a statement is re-used.
> Kathey pointed out some scenarios and said that we still need to do 2) - we
> need to send CLSQRY for all result sets of a statement when the statement is
> finalized. Sending CLSQRY command needs to be synchronized. Hence, we need to
> implement a mechanism similar to what is done in embedded driver finalizers.
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