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From Grant Ingersoll <>
Subject Re: memory leak during Lucene Search
Date Tue, 09 Sep 2008 18:23:11 GMT
Just chipping in that I recall there being a number of discussions on  
java-dev about ThreadLocal and web containers and how they should be  
handled.  Not sure if it pertains here or not, but you might find


You might also consider asking on java-dev in this case, which usually  
isn't recommended, but this is pretty low-level stuff and seems more  
appropriate there.  It does seem like a problem though and I'm not  
sure of the alternative just yet.

On Sep 7, 2008, at 1:35 AM, Chris Lu wrote:

> Unless my understanding is wrong, there is a memory leak for Lucene  
> search
> from Lucene-1195.(svn r659602, May23,2008)
> This patch brings in a ThreadLocal cache to TermInfosReader.
> It's usually recommended to keep the reader open, and reuse it when
> possible. In a common J2EE application, the http requests are usually
> handled by different threads. But since the cache is ThreadLocal,  
> the cache
> are not really usable by other threads. What's worse, the cache can  
> not be
> cleared by another thread!
> This leak is not so obvious usually. But my case is using  
> RAMDirectory,
> having several hundred megabytes. So one un-released resource is  
> obvious to
> me.
> Here is the reference tree:
>  |- directory of
>      |- file of
>          |- base of org.apache.lucene.index.CompoundFileReader 
> $CSIndexInput
>              |- input of org.apache.lucene.index.SegmentTermEnum
>                  |- value of java.lang.ThreadLocal$ThreadLocalMap 
> $Entry
> After I switched back to svn revision 659601, right before this  
> patch is
> checked in, the memory leak is gone.
> Although my case is RAMDirectory, I believe this will affect disk  
> based
> index also.

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