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From "Deepa Remesh (JIRA)" <derby-...@db.apache.org>
Subject [jira] Closed: (DERBY-1021) Perform cleanup actions which require synchronization outside the finalizer
Date Mon, 13 Mar 2006 21:43:41 GMT
     [ 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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