Chris Lu wrote:
The problem should be similar to what's talked about on this
discussion.
http://lucene.markmail.org/message/keosgz2c2yjc7qre?q=ThreadLocal
The "rough" conclusion of that thread is that, technically, this isn't
a memory leak but rather a "delayed freeing" problem. Ie, it may take
longer, possibly much longer, than you want for the memory to be freed.
There is a memory leak for Lucene search from Lucene-1195.(svn
r659602, May23,2008)
This patch brings in a ThreadLocal cache to TermInfosReader.
One thing that confuses me: TermInfosReader was already using a
ThreadLocal to cache the SegmentTermEnum instance. What was added in
this commit (for LUCENE-1195) was an LRU cache storing Term ->
TermInfo instances. But it seems like it's the SegmentTermEnum
instance that you're tracing below.
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:
org.apache.lucene.store.RAMDirectory
|- directory of org.apache.lucene.store.RAMFile
|- file of org.apache.lucene.store.RAMInputStream
|- base of org.apache.lucene.index.CompoundFileReader
$CSIndexInput
|- input of org.apache.lucene.index.SegmentTermEnum
|- value of java.lang.ThreadLocal$ThreadLocalMap
$Entry
So you have a RAMDir that has several hundred MB stored in it, that
you're done with yet through this path Lucene is keeping it alive?
Did you close the RAMDir? (which will null its fileMap and should
also free your memory).
Also, that reference tree doesn't show the ThreadResources class that
was added in that commit -- are you sure this reference tree wasn't
before the commit?
Mike
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