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From "Thomas Nielsen (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-1781) Process handles appear to be leaking in queries using an IN clause during concurrent DB access
Date Tue, 16 Oct 2007 07:25:50 GMT

    [ https://issues.apache.org/jira/browse/DERBY-1781?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12535168

Thomas Nielsen commented on DERBY-1781:

I attached the NB profiler to the NetworkServer running on a Java 6 VM, and had a quick look
around while running the repro. 

There are in excess of  300 "surviving generations" of objects, and 3 live DRDAConnThread's
after the first run. 
On the subsequent 2 runs of the repro I see GC being run, the number of surviving generations
is still increasing, and there are 3 additional DRDAConnThreads for each run.

Forcing manual GC via the profiler reduced the surviving generations to about 50% (~300) after
the third run. Additional GC runs does (understandably) not help.

The DRDAConnThreads are in "wait" state, but still live. I'm not sure what lifespan the DRDAConnThreads
are supposed to have at this moment. Wether they should stop when the client disconnects,
or if they are supposed to live for some time to serve probable next connections?

I'll have another look at where the surviving generations are/originate from.

> Process handles appear to be leaking in queries using an IN clause during concurrent
DB access
> ----------------------------------------------------------------------------------------------
>                 Key: DERBY-1781
>                 URL: https://issues.apache.org/jira/browse/DERBY-1781
>             Project: Derby
>          Issue Type: Bug
>          Components: SQL
>    Affects Versions:
>         Environment: Windows XP, Java 1.5.0_05
>            Reporter: Mark Hellkamp
>         Attachments: SqlStressTest.java
> We are currently using Derby embedded in our web application running on Windows. When
processing multiple concurrent requests we have noticed that the Java process handle count
continues to increase until the machine becomes unresponsive. I was able to isolate the problem
to Derby by running the database in network mode in another process. Further investigation
showed that the problem could be reproduced using a select statement that has an IN clause
with multiple entries on the primary key column. Spawning multiple threads running the same
query causes the handle count to increase considerably on the Derby process. The problem occurs
in version and (even worse) in both embedded and network mode. The attached
test program duplicates the problem. Start Derby in network mode (using startNetworkServer.bat)
and run the enclosed test program. The handle count on the Derby process will increase and
never go down short of restarting Derby. Using the handle count for the Derby process
goes somewhere between 1400-1500 with just two threads in my environment. 

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