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From robert engels <reng...@ix.netcom.com>
Subject Re: ThreadLocal causing memory leak with J2EE applications
Date Thu, 11 Sep 2008 05:01:48 GMT
Not really true. Java will preform a GC and clear weak/soft  
references before throwing an OOM.

In this case, the key will be cleared (since it is held in a weak  
reference), but the entry (referring to the value) will not be  
removed until later (when purge stale entries happens).  There is no  
"hook" to force the purge before an OOM is thrown.

Ideally, this would be a nice addition to Java GC - callbacks so that  
classes can discard "extra" memory if needed.  In most cases a  
SoftReference will accomplish this, but not in this case, as you  
don't want the cached 'enum' to ever be freed while still interating  
(otherwise boom).

On Sep 10, 2008, at 10:55 PM, Otis Gospodnetic wrote:

> Maybe I didn't read all messages in this thread, but Chris, isn't  
> what you are describing the nature of java?  You can call close(),  
> but close() can't guarantee that the JVM will free up all the  
> memory immediately.
>
> Also, what if you were to comment out that LRU stuff that you think  
> is problematic?  Does the OOM disappear?
>
> Otis
> --
> Sematext -- http://sematext.com/ -- Lucene - Solr - Nutch
>
>
> ----- Original Message ----
> From: Chris Lu <chris.lu@gmail.com>
> To: java-dev@lucene.apache.org
> Sent: Wednesday, September 10, 2008 4:19:00 PM
> Subject: Re: ThreadLocal causing memory leak with J2EE applications
>
> Well, the code is correct, because it can work by avoiding this  
> trap. But it failed to act as a good API.
>
> I learned the inside details from you. I am not the only one that's  
> trapped. And more users will likely be trapped again, unless  
> javadoc to describe the close() function is changed. Actually, I  
> didn't look at the javadoc of close(), because, shouldn't close()  
> means close(), not uncontrollably delayed resource releasing? So I  
> fear just changing the javadoc is not enough.
>
> -- 
> Chris Lu
> -------------------------
> Instant Scalable Full-Text Search On Any Database/Application
> site: http://www.dbsight.net
> demo: http://search.dbsight.com
> Lucene Database Search in 3 minutes: http://wiki.dbsight.com/ 
> index.php?title=Create_Lucene_Database_Search_in_3_minutes
> DBSight customer, a shopping comparison site, (anonymous per  
> request) got 2.6 Million Euro funding!
>
>
> On Wed, Sep 10, 2008 at 1:03 PM, robert engels  
> <rengels@ix.netcom.com> wrote:
> Always your prerogative.
>
> On Sep 10, 2008, at 1:15 PM, Chris Lu wrote:
>
>> Actually I am done with it by simply downgrading and not to use  
>> r659602 and later.
>> The old version is more clean and consistent with the API and close 
>> () does mean close, not something complicated and unknown to most  
>> users, which almost feels like a trap. And later on, if no changes  
>> happened for this file, I will have to upgrade Lucene and manually  
>> remove the patch Lucene-1195.
>>
>> -- 
>> Chris Lu
>> -------------------------
>> Instant Scalable Full-Text Search On Any Database/Application
>> site: http://www.dbsight.net
>> demo: http://search.dbsight.com
>> Lucene Database Search in 3 minutes: http://wiki.dbsight.com/ 
>> index.php?title=Create_Lucene_Database_Search_in_3_minutes
>> DBSight customer, a shopping comparison site, (anonymous per  
>> request) got 2.6 Million Euro funding!
>>
>> On Wed, Sep 10, 2008 at 10:56 AM, robert engels  
>> <rengels@ix.netcom.com> wrote:
>> Why not just use reopen() and be done with it???
>>
>> On Sep 10, 2008, at 12:48 PM, Chris Lu wrote:
>>
>>> Yeah, the timing is different. But it's an unknown, undetermined,  
>>> and uncontrollable time...
>>>
>>> We can not ask the user,
>>>
>>> while(memory is low){
>>>   sleep(1000);
>>> }
>>> do_the_real_thing_an_hour_later
>>>
>>>
>>> -- 
>>> Chris Lu
>>> -------------------------
>>> Instant Scalable Full-Text Search On Any Database/Application
>>> site: http://www.dbsight.net
>>> demo: http://search.dbsight.com
>>> Lucene Database Search in 3 minutes: http://wiki.dbsight.com/ 
>>> index.php?title=Create_Lucene_Database_Search_in_3_minutes
>>> DBSight customer, a shopping comparison site, (anonymous per  
>>> request) got 2.6 Million Euro funding!
>>>
>>> On Wed, Sep 10, 2008 at 10:39 AM, robert engels  
>>> <rengels@ix.netcom.com> wrote:
>>> Close() does work - it is just that the memory may not be freed  
>>> until much later...
>>>
>>> When working with VERY LARGE objects, this can be a problem.
>>>
>>> On Sep 10, 2008, at 12:36 PM, Chris Lu wrote:
>>>
>>>> Thanks for the analysis, really appreciate it, and I agree with  
>>>> it. But...
>>>>
>>>> This is really a normal J2EE use case. The threads seldom die.
>>>> Doesn't that mean closing the RAMDirectory doesn't work for J2EE  
>>>> applications?
>>>> And only reopen() works?
>>>> And close() doesn't release the resources? duh...
>>>>
>>>> I can only say this is a problem to be cleaned up.
>>>>
>>>> -- 
>>>> Chris Lu
>>>> -------------------------
>>>> Instant Scalable Full-Text Search On Any Database/Application
>>>> site: http://www.dbsight.net
>>>> demo: http://search.dbsight.com
>>>> Lucene Database Search in 3 minutes: http://wiki.dbsight.com/ 
>>>> index.php?title=Create_Lucene_Database_Search_in_3_minutes
>>>> DBSight customer, a shopping comparison site, (anonymous per  
>>>> request) got 2.6 Million Euro funding!
>>>>
>>>>
>>>> On Wed, Sep 10, 2008 at 9:10 AM, robert engels  
>>>> <rengels@ix.netcom.com> wrote:
>>>> You do not need to create a new RAMDirectory - just write to the  
>>>> existing one, and then reopen() the IndexReader using it.
>>>>
>>>> This will prevent lots of big objects being created. This may be  
>>>> the source of your problem.
>>>>
>>>> Even if the Segment is closed, the ThreadLocal will no longer be  
>>>> referenced, but there will still be a reference to the  
>>>> SegmentTermEnum (which will be cleared when the thread dies, or  
>>>> "most likely" when new thread locals on that thread a created,  
>>>> so here is a potential problem.
>>>>
>>>> Thread 1 does a search, creates a thread local that references  
>>>> the RAMDir (A).
>>>> Thread 2 does a search, creates a thread local that references  
>>>> the RAMDir (A).
>>>>
>>>> All readers, are closed on RAMDir (A).
>>>>
>>>> A new RAMDir (B) is opened.
>>>>
>>>> There may still be references in the thread local maps to RAMDir  
>>>> A (since no new thread local have been created yet).
>>>>
>>>> So you may get OOM depending on the size of the RAMDir (since  
>>>> you would need room for more than 1).  If you extend this out  
>>>> with lots of threads that don't run very often, you can see how  
>>>> you could easily run out of memory.  "I think" that ThreadLocal  
>>>> should use a ReferenceQueue so stale object slots can be  
>>>> reclaimed as soon as the key is dereferenced - but that is an  
>>>> issue for SUN.
>>>>
>>>> This is why you don't want to create new RAMDirs.
>>>>
>>>> A good rule of thumb - don't keep references to large objects in  
>>>> ThreadLocal (especially indirectly).  If needed, use a "key",  
>>>> and then read the cache using a the "key".
>>>> This would be something for the Lucene folks to change.
>>>>
>>>> On Sep 10, 2008, at 10:44 AM, Chris Lu wrote:
>>>>
>>>>> I am really want to find out where I am doing wrong, if that's  
>>>>> the case.
>>>>>
>>>>> Yes. I have made certain that I closed all Readers/Searchers,  
>>>>> and verified that through memory profiler.
>>>>>
>>>>> Yes. I am creating new RAMDirectory. But that's the problem. I  
>>>>> need to update the content. Sure, if no content update and  
>>>>> everything the same, of course no OOM.
>>>>>
>>>>> Yes. No guarantee of the thread schedule. But that's the  
>>>>> problem. If Lucene is using ThreadLocal to cache lots of things  
>>>>> by the Thread as the key, and no idea when it'll be released.  
>>>>> Of course ThreadLocal is not Lucene's problem...
>>>>>
>>>>> Chris
>>>>>
>>>>> On Wed, Sep 10, 2008 at 8:34 AM, robert engels  
>>>>> <rengels@ix.netcom.com> wrote:
>>>>> It is basic Java. Threads are not guaranteed to run on any sort  
>>>>> of schedule. If you create lots of large objects in one thread,  
>>>>> releasing them in another, there is a good chance you will get  
>>>>> an OOM (since the releasing thread may not run before the OOM  
>>>>> occurs)...  This is not Lucene specific by any means.
>>>>>
>>>>> It is a misunderstanding on your part about how GC works.
>>>>>
>>>>> I assume you must at some point be creating new RAMDirectories  
>>>>> - otherwise the memory would never really increase, since the  
>>>>> IndexReader/enums/etc are not very large...
>>>>>
>>>>> When you create a new RAMDirectories, you need to BE  
>>>>> CERTAIN !!! that the other IndexReaders/Searchers using the old  
>>>>> RAMDirectory are ALL CLOSED, otherwise their memory will still  
>>>>> be in use, which leads to your OOM...
>>>>>
>>>>>
>>>>> On Sep 10, 2008, at 10:16 AM, Chris Lu wrote:
>>>>>
>>>>>> I do not believe I am making any mistake. Actually I just got  
>>>>>> an email from another user, complaining about the same thing.  
>>>>>> And I am having the same usage pattern.
>>>>>>
>>>>>> After the reader is opened, the RAMDirectory is shared by  
>>>>>> several objects.
>>>>>> There is one instance of RAMDirectory in the memory, and it is  
>>>>>> holding lots of memory, which is expected.
>>>>>>
>>>>>> If I close the reader in the same thread that has opened it,  
>>>>>> the RAMDirectory is gone from the memory.
>>>>>> If I close the reader in other threads, the RAMDirectory is  
>>>>>> left in the memory, referenced along the tree I draw in the  
>>>>>> first email.
>>>>>>
>>>>>> I do not think the usage is wrong. Period.
>>>>>>
>>>>>> -------------------------------------
>>>>>> Hi,
>>>>>>
>>>>>>    i found a forum post from you here [1] where you mention  
>>>>>> that you
>>>>>> have a memory leak using the lucene ram directory. I'd like to  
>>>>>> ask you
>>>>>> if you already have resolved the problem and how you did it or  
>>>>>> maybe
>>>>>> you know where i can read about the solution. We are using
>>>>>> RAMDirectory too and figured out, that over time the memory
>>>>>> consumption raises and raises until the system breaks down but  
>>>>>> only
>>>>>> when we performing much index updates. if we only create the  
>>>>>> index and
>>>>>> don't do nothing except searching it, it work fine.
>>>>>>
>>>>>> maybe you can give me a hint or a link,
>>>>>> greetz,
>>>>>> -------------------------------------
>>>>>>
>>>>>> -- 
>>>>>> Chris Lu
>>>>>> -------------------------
>>>>>> Instant Scalable Full-Text Search On Any Database/Application
>>>>>> site: http://www.dbsight.net
>>>>>> demo: http://search.dbsight.com
>>>>>> Lucene Database Search in 3 minutes: http://wiki.dbsight.com/ 
>>>>>> index.php?title=Create_Lucene_Database_Search_in_3_minutes
>>>>>> DBSight customer, a shopping comparison site, (anonymous per  
>>>>>> request) got 2.6 Million Euro funding!
>>>>>>
>>>>>> On Wed, Sep 10, 2008 at 7:12 AM, robert engels  
>>>>>> <rengels@ix.netcom.com> wrote:
>>>>>> Sorry, but I am fairly certain you are mistaken.
>>>>>>
>>>>>> If you only have a single IndexReader, the RAMDirectory will  
>>>>>> be shared in all cases.
>>>>>>
>>>>>> The only memory growth is any buffer space allocated by an  
>>>>>> IndexInput (used in many places and cached).
>>>>>>
>>>>>> Normally the IndexInput created by a RAMDirectory do not have  
>>>>>> any buffer allocated, since the underlying store is already in  
>>>>>> memory.
>>>>>>
>>>>>> You have some other problem in your code...
>>>>>>
>>>>>> On Sep 10, 2008, at 1:10 AM, Chris Lu wrote:
>>>>>>
>>>>>>> Actually, even I only use one IndexReader, some resources are
 
>>>>>>> cached via the ThreadLocal cache, and can not be released  
>>>>>>> unless all threads do the close action.
>>>>>>>
>>>>>>> SegmentTermEnum itself is small, but it holds RAMDirectory  
>>>>>>> along the path, which is big.
>>>>>>>
>>>>>>> -- 
>>>>>>> Chris Lu
>>>>>>> -------------------------
>>>>>>> Instant Scalable Full-Text Search On Any Database/Application
>>>>>>> site: http://www.dbsight.net
>>>>>>> demo: http://search.dbsight.com
>>>>>>> Lucene Database Search in 3 minutes: http://wiki.dbsight.com/

>>>>>>> index.php?title=Create_Lucene_Database_Search_in_3_minutes
>>>>>>> DBSight customer, a shopping comparison site, (anonymous per
 
>>>>>>> request) got 2.6 Million Euro funding!
>>>>>>>
>>>>>>> On Tue, Sep 9, 2008 at 10:43 PM, robert engels  
>>>>>>> <rengels@ix.netcom.com> wrote:
>>>>>>> You do not need a pool of IndexReaders...
>>>>>>>
>>>>>>> It does not matter what class it is, what matters is the  
>>>>>>> class that ultimately holds the reference.
>>>>>>>
>>>>>>> If the IndexReader is never closed, the SegmentReader(s) is 

>>>>>>> never closed, so the thread local in TermInfosReader is not 

>>>>>>> cleared (because the thread never dies). So you will get one
 
>>>>>>> SegmentTermEnum, per thread * per segment.
>>>>>>>
>>>>>>> The SegmentTermEnum is not a large object, so even if you had
 
>>>>>>> 100 threads, and 100 segments, for 10k instances, seems hard
 
>>>>>>> to believe that is the source of your memory issue.
>>>>>>>
>>>>>>> The SegmentTermEnum is cached by thread since it needs to  
>>>>>>> enumerate the terms, not having a per thread cache, would  
>>>>>>> lead to lots of random access when multiple threads read the
 
>>>>>>> index - very slow.
>>>>>>>
>>>>>>> You need to keep in mind, what if every thread was executing
 
>>>>>>> a search simultaneously - you would still have 100x100  
>>>>>>> SegmentTermEnum instances anyway !  The only way to prevent 

>>>>>>> that would be to create and destroy the SegmentTermEnum on  
>>>>>>> each call (opening and seeking to the proper spot) - which  
>>>>>>> would be SLOW SLOW SLOW.
>>>>>>>
>>>>>>> On Sep 10, 2008, at 12:19 AM, Chris Lu wrote:
>>>>>>>
>>>>>>>> I have tried to create an IndexReader pool and dynamically
 
>>>>>>>> create searcher. But the memory leak is the same. It's not
 
>>>>>>>> related to the Searcher class specifically, but the  
>>>>>>>> SegmentTermEnum in TermInfosReader.
>>>>>>>>
>>>>>>>> -- 
>>>>>>>> Chris Lu
>>>>>>>> -------------------------
>>>>>>>> Instant Scalable Full-Text Search On Any Database/Application
>>>>>>>> site: http://www.dbsight.net
>>>>>>>> demo: http://search.dbsight.com
>>>>>>>> Lucene Database Search in 3 minutes: http://wiki.dbsight.com/

>>>>>>>> index.php?title=Create_Lucene_Database_Search_in_3_minutes
>>>>>>>> DBSight customer, a shopping comparison site, (anonymous
per  
>>>>>>>> request) got 2.6 Million Euro funding!
>>>>>>>>
>>>>>>>> On Tue, Sep 9, 2008 at 10:14 PM, robert engels  
>>>>>>>> <rengels@ix.netcom.com> wrote:
>>>>>>>> A searcher uses an IndexReader - the IndexReader is slow
to  
>>>>>>>> open, not a Searcher. And searchers can share an IndexReader.
>>>>>>>>
>>>>>>>> You want to create a single shared (across all threads/ 
>>>>>>>> users) IndexReader (usually), and create an Searcher as 

>>>>>>>> needed and dispose.  It is VERY CHEAP to create the Searcher.
>>>>>>>>
>>>>>>>> I am fairly certain the javadoc on Searcher is incorrect.
  
>>>>>>>> The warning "For performance reasons it is recommended to
 
>>>>>>>> open onlyone IndexSearcher and use it for all of your  
>>>>>>>> searches" is not true in the case where an IndexReader is
 
>>>>>>>> passed to the ctor.
>>>>>>>>
>>>>>>>> Any caching should USUALLY be performed at the IndexReader
 
>>>>>>>> level.
>>>>>>>>
>>>>>>>> You are most likely using the "path" ctor, and that is the
 
>>>>>>>> source of your problems, as multiple IndexReader instances
 
>>>>>>>> are being created, and thus the memory use.
>>>>>>>>
>>>>>>>>
>>>>>>>> On Sep 9, 2008, at 11:44 PM, Chris Lu wrote:
>>>>>>>>
>>>>>>>>> On J2EE environment, usually there is a searcher pool
with  
>>>>>>>>> several searchers open.
>>>>>>>>> The speed to opening a large index for every user is
not  
>>>>>>>>> acceptable.
>>>>>>>>>
>>>>>>>>> -- 
>>>>>>>>> Chris Lu
>>>>>>>>> -------------------------
>>>>>>>>> Instant Scalable Full-Text Search On Any Database/Application
>>>>>>>>> site: http://www.dbsight.net
>>>>>>>>> demo: http://search.dbsight.com
>>>>>>>>> Lucene Database Search in 3 minutes: http:// 
>>>>>>>>> wiki.dbsight.com/index.php? 
>>>>>>>>> title=Create_Lucene_Database_Search_in_3_minutes
>>>>>>>>> DBSight customer, a shopping comparison site, (anonymous
 
>>>>>>>>> per request) got 2.6 Million Euro funding!
>>>>>>>>>
>>>>>>>>> On Tue, Sep 9, 2008 at 9:03 PM, robert engels  
>>>>>>>>> <rengels@ix.netcom.com> wrote:
>>>>>>>>> You need to close the searcher within the thread that
is  
>>>>>>>>> using it, in order to have it cleaned up quickly... usually
 
>>>>>>>>> right after you display the page of results.
>>>>>>>>>
>>>>>>>>> If you are keeping multiple searcher refs across multiple
 
>>>>>>>>> threads for paging/whatever, you have not coded it correctly.
>>>>>>>>>
>>>>>>>>> Imagine 10,000 users - storing a searcher for each one
is  
>>>>>>>>> not going to work...
>>>>>>>>>
>>>>>>>>> On Sep 9, 2008, at 10:21 PM, Chris Lu wrote:
>>>>>>>>>
>>>>>>>>>> Right, in a sense I can not release it from another
 
>>>>>>>>>> thread. But that's the problem.
>>>>>>>>>>
>>>>>>>>>> It's a J2EE environment, all threads are kind of
equal.  
>>>>>>>>>> It's simply not possible to iterate through all threads
to  
>>>>>>>>>> close the searcher, thus releasing the ThreadLocal
cache.
>>>>>>>>>> Unless Lucene is not recommended for J2EE environment,
 
>>>>>>>>>> this has to be fixed.
>>>>>>>>>>
>>>>>>>>>> -- 
>>>>>>>>>> Chris Lu
>>>>>>>>>> -------------------------
>>>>>>>>>> Instant Scalable Full-Text Search On Any Database/Application
>>>>>>>>>> site: http://www.dbsight.net
>>>>>>>>>> demo: http://search.dbsight.com
>>>>>>>>>> Lucene Database Search in 3 minutes: http:// 
>>>>>>>>>> wiki.dbsight.com/index.php? 
>>>>>>>>>> title=Create_Lucene_Database_Search_in_3_minutes
>>>>>>>>>> DBSight customer, a shopping comparison site, (anonymous
 
>>>>>>>>>> per request) got 2.6 Million Euro funding!
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> On Tue, Sep 9, 2008 at 8:14 PM, robert engels  
>>>>>>>>>> <rengels@ix.netcom.com> wrote:
>>>>>>>>>> Your code is not correct. You cannot release it on
another  
>>>>>>>>>> thread - the first thread may creating hundreds/thousands
 
>>>>>>>>>> of instances before the other thread ever runs...
>>>>>>>>>>
>>>>>>>>>> On Sep 9, 2008, at 10:10 PM, Chris Lu wrote:
>>>>>>>>>>
>>>>>>>>>>> If I release it on the thread that's creating
the  
>>>>>>>>>>> searcher, by setting searcher=null, everything
is fine,  
>>>>>>>>>>> the memory is released very cleanly.
>>>>>>>>>>> My load test was to repeatedly create a searcher
on a  
>>>>>>>>>>> RAMDirectory and release it on another thread.
The test  
>>>>>>>>>>> will quickly go to OOM after several runs. I
set the heap  
>>>>>>>>>>> size to be 1024M, and the RAMDirectory is of
size 250M.  
>>>>>>>>>>> Using some profiling tool, the used size simply
stepped  
>>>>>>>>>>> up pretty obviously by 250M.
>>>>>>>>>>>
>>>>>>>>>>> I think we should not rely on something that's
a "maybe"  
>>>>>>>>>>> behavior, especially for a general purpose library.
>>>>>>>>>>>
>>>>>>>>>>> Since it's a multi-threaded env, the thread that's
 
>>>>>>>>>>> creating the entries in the LRU cache may not
go away  
>>>>>>>>>>> quickly(actually most, if not all, application
servers  
>>>>>>>>>>> will try to reuse threads), so the LRU cache,
which uses  
>>>>>>>>>>> thread as the key, can not be released, so the
 
>>>>>>>>>>> SegmentTermEnum which is in the same class can
not be  
>>>>>>>>>>> released.
>>>>>>>>>>>
>>>>>>>>>>> And yes, I close the RAMDirectory, and the fileMap
is  
>>>>>>>>>>> released. I verified that through the profiler
by  
>>>>>>>>>>> directly checking the values in the snapshot.
>>>>>>>>>>>
>>>>>>>>>>> Pretty sure the reference tree wasn't like this
using  
>>>>>>>>>>> code before this commit, because after close
the searcher  
>>>>>>>>>>> in another thread, the RAMDirectory totally disappeared
 
>>>>>>>>>>> from the memory snapshot.
>>>>>>>>>>>
>>>>>>>>>>> -- 
>>>>>>>>>>> Chris Lu
>>>>>>>>>>> -------------------------
>>>>>>>>>>> Instant Scalable Full-Text Search On Any Database/

>>>>>>>>>>> Application
>>>>>>>>>>> site: http://www.dbsight.net
>>>>>>>>>>> demo: http://search.dbsight.com
>>>>>>>>>>> Lucene Database Search in 3 minutes: http://

>>>>>>>>>>> wiki.dbsight.com/index.php? 
>>>>>>>>>>> title=Create_Lucene_Database_Search_in_3_minutes
>>>>>>>>>>> DBSight customer, a shopping comparison site,
(anonymous  
>>>>>>>>>>> per request) got 2.6 Million Euro funding!
>>>>>>>>>>>
>>>>>>>>>>> On Tue, Sep 9, 2008 at 5:03 PM, Michael McCandless
 
>>>>>>>>>>> <lucene@mikemccandless.com> wrote:
>>>>>>>>>>>
>>>>>>>>>>> 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
>>>>>>>>>>>
>>>>>>>>>>> ------------------------------------------------------------

>>>>>>>>>>> ---------
>>>>>>>>>>> To unsubscribe, e-mail: java-dev- 
>>>>>>>>>>> unsubscribe@lucene.apache.org
>>>>>>>>>>> For additional commands, e-mail: java-dev- 
>>>>>>>>>>> help@lucene.apache.org
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> -- 
>>>>>>>>>>> Chris Lu
>>>>>>>>>>> -------------------------
>>>>>>>>>>> Instant Scalable Full-Text Search On Any Database/

>>>>>>>>>>> Application
>>>>>>>>>>> site: http://www.dbsight.net
>>>>>>>>>>> demo: http://search.dbsight.com
>>>>>>>>>>> Lucene Database Search in 3 minutes: http://

>>>>>>>>>>> wiki.dbsight.com/index.php? 
>>>>>>>>>>> title=Create_Lucene_Database_Search_in_3_minutes
>>>>>>>>>>> DBSight customer, a shopping comparison site,
(anonymous  
>>>>>>>>>>> per request) got 2.6 Million Euro funding!
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> -- 
>>>>> Chris Lu
>>>>> -------------------------
>>>>> Instant Scalable Full-Text Search On Any Database/Application
>>>>> site: http://www.dbsight.net
>>>>> demo: http://search.dbsight.com
>>>>> Lucene Database Search in 3 minutes: http://wiki.dbsight.com/ 
>>>>> index.php?title=Create_Lucene_Database_Search_in_3_minutes
>>>>> DBSight customer, a shopping comparison site, (anonymous per  
>>>>> request) got 2.6 Million Euro funding!
>>>>
>>>>
>>>>
>>>>
>>>
>>>
>>>
>>
>>
>>
>>
>
>
>
>


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