From java-dev-return-27318-apmail-lucene-java-dev-archive=lucene.apache.org@lucene.apache.org Wed Sep 10 15:17:21 2008 Return-Path: Delivered-To: apmail-lucene-java-dev-archive@www.apache.org Received: (qmail 8362 invoked from network); 10 Sep 2008 15:17:20 -0000 Received: from hermes.apache.org (HELO mail.apache.org) (140.211.11.2) by minotaur.apache.org with SMTP; 10 Sep 2008 15:17:20 -0000 Received: (qmail 19881 invoked by uid 500); 10 Sep 2008 15:17:14 -0000 Delivered-To: apmail-lucene-java-dev-archive@lucene.apache.org Received: (qmail 19838 invoked by uid 500); 10 Sep 2008 15:17:14 -0000 Mailing-List: contact java-dev-help@lucene.apache.org; run by ezmlm Precedence: bulk List-Help: List-Unsubscribe: List-Post: List-Id: Reply-To: java-dev@lucene.apache.org Delivered-To: mailing list java-dev@lucene.apache.org Received: (qmail 19829 invoked by uid 99); 10 Sep 2008 15:17:14 -0000 Received: from athena.apache.org (HELO athena.apache.org) (140.211.11.136) by apache.org (qpsmtpd/0.29) with ESMTP; Wed, 10 Sep 2008 08:17:14 -0700 X-ASF-Spam-Status: No, hits=2.0 required=10.0 tests=HTML_MESSAGE,SPF_PASS X-Spam-Check-By: apache.org Received-SPF: pass (athena.apache.org: domain of chris.lu@gmail.com designates 74.125.46.28 as permitted sender) Received: from [74.125.46.28] (HELO yw-out-2324.google.com) (74.125.46.28) by apache.org (qpsmtpd/0.29) with ESMTP; Wed, 10 Sep 2008 15:16:14 +0000 Received: by yw-out-2324.google.com with SMTP id 3so441600ywj.5 for ; Wed, 10 Sep 2008 08:16:45 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:received:received:message-id:date:from:to :subject:in-reply-to:mime-version:content-type:references; bh=+GpBcAsOXxk9dARgnoqAgMHdJihJ1e2vvycg2Wk+q/M=; b=ctX+rVVvWs/48MpAeuMMpEFe91gpGbklqPL7bNvtvifhtu3ti0COFhA5rQ6KH6XY9J Bhflm4RlKeU4zkA9FtaNwbD5dgPN9YRnPq3MxXSk/+ONjnW2gTUKN5E/mcVMNxJYqci6 uSxGhsSu7nJmLdR1SaQjnzLGJMQWx0Bik5TWE= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=message-id:date:from:to:subject:in-reply-to:mime-version :content-type:references; b=OLTmTGrk74IsxJwG+qMhwO9DkKNrabCwmpWTT+8sLBmVx0IUlbh6cOcnu4H4QLkVr2 4L5etkXtHiLyeqvJEnWKkMlJbitGXnsaEsGHP3uN00DcLPCC/ESOyJaONP5/LK+P2mh4 KVrzQh2qhEslAJHmqyylwoWmAbA60PCkqVWuc= Received: by 10.142.140.14 with SMTP id n14mr464623wfd.247.1221059804604; Wed, 10 Sep 2008 08:16:44 -0700 (PDT) Received: by 10.142.111.8 with HTTP; Wed, 10 Sep 2008 08:16:44 -0700 (PDT) Message-ID: <6e3ae6310809100816q248cfef8pa8933a383de76003@mail.gmail.com> Date: Wed, 10 Sep 2008 08:16:44 -0700 From: "Chris Lu" To: java-dev@lucene.apache.org Subject: Re: ThreadLocal causing memory leak with J2EE applications In-Reply-To: <0FB358D2-EC2F-429D-B892-DAF8BFB47345@ix.netcom.com> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_Part_148193_22807910.1221059804589" References: <6e3ae6310809091157j7a9fe46bxcc31f6e63305fcdc@mail.gmail.com> <6e3ae6310809092021n3943a9f0xdfc3d62dbf0d2833@mail.gmail.com> <98A7B5A6-2ECA-4640-815D-17AE7EB5445E@ix.netcom.com> <6e3ae6310809092144v153d634ejea5c2372f72d1951@mail.gmail.com> <1C021C48-DC16-4DE1-BB7C-B89B67A5A685@ix.netcom.com> <6e3ae6310809092219w22517a47w8d29df4eb8e4a2d@mail.gmail.com> <22848D3B-560D-46FA-A198-9C6F9A145999@ix.netcom.com> <6e3ae6310809092310s67fc08f8mc17f4d92c8926336@mail.gmail.com> <0FB358D2-EC2F-429D-B892-DAF8BFB47345@ix.netcom.com> X-Virus-Checked: Checked by ClamAV on apache.org ------=_Part_148193_22807910.1221059804589 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline 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 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 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 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 only one 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 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 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! >>>>> >>>>> >>>>> >>>> >>>> >>>> >>>> >>> >>> >>> >> >> >> > > > > ------=_Part_148193_22807910.1221059804589 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Content-Disposition: inline
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 opene= d, 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 clo= se the reader in the same thread that has opened it, the RAMDirectory is go= ne from the memory.
If I close the reader in other threads, the RAMDirectory is left in th= e 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 Scalab= le Full-Text Search On Any Database/Application
site: http://www.dbsight.net
demo: http://search.dbsight.comLucene Database Search in 3 minutes: http://wiki.db= sight.com/index.php?title=3DCreate_Lucene_Database_Search_in_3_minutes<= br> 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 case= s.

The only memory growth is any buffer space allo= cated by an IndexInput (used in many places and cached).

Normally the IndexInput created by a RAMDirectory do no= t have any buffer allocated, since the underlying store is already in memor= y.

You have some other problem in your code...

On Sep 10, 20= 08, 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 threa= ds do the close action.

SegmentTermEnum itself is small, but it holds RAMD= irectory along the path, which is big.

-- 
Chris Lu-------------------------
Instant Scalable Full-Text Search On Any Dat= abase/Application
site: http://www.dbsig= ht.net
demo: http://search.dbsight.com
Lucene Database Search in 3 minutes: http://wiki.dbsight.com/index.php?titl= e=3DCreate_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 w= hat class it is, what matters is the class that ultimately holds the refere= nce.

If the IndexReader is never closed, the SegmentRea= der(s) is never closed, so the thread local in TermInfosReader is not clear= ed (because the thread never dies). So you will get one SegmentTermEnum, pe= r 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 bel= ieve that is the source of your memory issue.

The SegmentTermEnum is cached by thread since it needs to enumerate the ter= ms, 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 simul= taneously - you would still have 100x100 SegmentTermEnum instances anyway !=  The only way to prevent that would be to create and destroy the Segm= entTermEnum on each call (opening and seeking to the proper spot) - which w= ould be SLOW SLOW SLOW.

On Sep 1= 0, 2008, at 12:19 AM, Chris Lu wrote:

I have tried to create an IndexReader pool and dynamically c= reate searcher. But the memory leak is the same. It's not related to th= e 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<= /a>
Lucene Database Search in 3 minutes: http://wiki.dbsight.com/index.php?title=3DCreate_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 sea= rcher 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/user= s) IndexReader (usually), and create an Searcher as needed and dispose. &nb= sp;It is VERY CHEAP to create the Searcher.

I am = fairly certain the javadoc on Searcher is incorrect.  The warning &quo= t;For performance reasons it is recommended<= font face=3D"Monaco" size=3D"3" style=3D"font:11.0px Monaco"> to open only<= font face=3D"Monaco" size=3D"3" style=3D"font:11.0px Monaco"> one IndexSearcher and= use it for all of your= searches" is not true in the case where an IndexReader is p= assed to the ctor.

Any caching should USUALLY be performed at the In= dexReader level.

You are most likely using the &qu= ot;path" ctor, and that is the source of your problems, as multiple In= dexReader 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 searc= her 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://searc= h.dbsight.com
Lucene Database Search in 3 minutes: http://wiki.dbsight.com/index.php?title=3DCreate_Luc= ene_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> w= rote:
You ne= ed to close the searcher within the thread that is using it, in order to ha= ve it cleaned up quickly... usually right after you display the page of res= ults.

If you are keeping multiple searcher refs across multiple t= hreads for paging/whatever, you have not coded it correctly.
Imagine 10,000 users - storing a searcher for each one is not g= oing to work...

On Sep 9, 2008, at 10:21 PM, = Chris Lu wrote:

R= ight, in a sense I can not release it from another thread. But that's t= he problem.

It's a J2EE environment, all threads are kind of e= qual. It's simply not possible to iterate through all threads to close = the searcher, thus releasing the ThreadLocal cache.
Unless Lucen= e 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=3DCreate_Lucene_Database_Search_= in_3_minutes
DBSight customer, a shopping comparison site, (anonymous per request) got = 2.6 Million Euro funding!


On Tue, Se= p 9, 2008 at 8:14 PM, robert engels <rengels@ix.netcom.com> wrote:
Your c= ode is not correct. You cannot release it on another thread - the first thr= ead may creating hundreds/thousands of instances before the other thread ev= er runs...

On Sep 9, 2008, at 10:10 PM, Chris Lu = wrote:

If I releas= e it on the thread that's creating the searcher, by setting searcher=3D= null, everything is fine, the memory is released very cleanly.
My load test was to repeatedly create a searcher on a RAMDirectory an= d release it on another thread. The test will quickly go to OOM after sever= al runs. I set the heap size to be 1024M, and the RAMDirectory is of size 2= 50M. Using some profiling tool, the used size simply stepped up pretty obvi= ously by 250M.

I think we should not rely on something that'= ;s a "maybe" behavior, especially for a general purpose library.<= /div>

Since it's a multi-threaded env, the thread th= at's creating the entries in the LRU cache may not go away quickly(actu= ally most, if not all, application servers will try to reuse threads), so t= he LRU cache, which uses thread as the key, can not be released, so th= e SegmentTermEnum which is in the same class can not be released.

And yes, I close the RAMDirectory, and the fileM= ap is released. I verified that through the profiler by directly checking t= he values in the snapshot.

Pretty sure the referen= ce tree wasn't like this using code before this commit, because after c= lose the searcher in another thread, the RAMDirectory totally disappeared f= rom the memory snapshot.

-- 
Chris Lu
-------------------------
Instant Scal= able 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=3DCreate_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:

The "rough" conclusion of that thread i= s that, technically, this isn't a memory leak but rather a "delaye= d 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 Lucen= e search from Lucene-1195.(svn r659602, May23,2008)

This patch bri= ngs in a ThreadLocal cache to TermInfosReader.

One thing that confuses me: TermInfosReader was a= lready using a ThreadLocal to cache the SegmentTermEnum instance.  Wha= t was added in this commit (for LUCENE-1195) was an LRU cache storing Term = -> TermInfo instances.  But it seems like it's the SegmentTermE= num instance that you're tracing below.


It's usually recommended to = keep the reader open, and reuse it when
possible. In a common J2EE appl= ication, the http requests are usually
handled by different threads. But since the cache is ThreadLocal, the cach= e
are not really usable by other threads. What's worse, the cache c= an not be
cleared by another thread!

This leak is not so obvio= us usually. But my case is using RAMDirectory,
having several hundred megabytes. So one un-released resource is obvious t= o
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.CompoundFil= eReader$CSIndexInput
            |- input= of org.apache.lucene.index.SegmentTermEnum
       =         |- value of java.lang.ThreadLocal$ThreadLocalM= ap$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 kee= ping it alive?

Did you close the RAMDir?  (which will null it= s 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
Fo= r additional commands, e-mail: java-dev-help@lucene.apache.org




--
Chris Lu
-----= --------------------
Instant Scalable Full-Text Search On Any Database/A= pplication
site: ht= tp://www.dbsight.net
demo: http://searc= h.dbsight.com
Lucene Database Search in 3 minutes: http://wiki.dbsight.com/index.php?title=3DCreate_Luc= ene_Database_Search_in_3_minutes
DBSight customer, a shopping comparison site, (anonymous per request) got = 2.6 Million Euro funding!







=








<= /div>

------=_Part_148193_22807910.1221059804589--