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Date: Wed, 22 Nov 2006 10:11:50 +0900
From: "Trustin Lee" <trustin@gmail.com>
To: "Apache Directory Developers List" <dev@directory.apache.org>
Subject: Re: Warning: serious VM leak/bug with BlockingQueue & polling
 timeouts
In-Reply-To: <pan.2006.11.21.20.14.34.954250@wizards.de>
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References: <pan.2006.11.21.20.14.34.954250@wizards.de>

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On 11/22/06, Holger Hoffstaette <holger@wizards.de> wrote:
>
>
> Here's a heads up for those of you who have the source handy to check.
>
> Both JDK 1.5 and 1.6 have serious confirmed bugs that leak unreclaimable
> memory and will bring *idle* servers down, e.g. during the night or over
> the weekend when load is low or nonexistent. For more information see
> http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6460501 and related.
>
> In a nutshell BlockingQueue.poll(duration, TimeUnit) will leak *when that
> wait times out*; it will not leak when something is returned from the
> queue, as is the case with uninterrupted non-timed polling.
>
> The bug is confirmed and serious because it triggers extremely nasty GC
> panic that has the potential to bring the whole machine down due to
> excessive CPU spinning and unresponsiveness of the VM to external signals.
>
> I think it would be good if someone with the source would do a quick "find
> all references to method" to see if and how Mina is affected by this. I
> would not be surprised if this is the reason behind some reported leaks -
> polling with timeout is extremely useful for service scheduling in various
> forms and generally preferrable to complete blocking.


Wow, this is shocking.  Even Doug Lea and his co-workers make a mistake! :)
I think the reason why this bug is found so late is because most people
doesn't specify the polling timeout like we didn't for MINA.

Trustin
-- 
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On 11/22/06, <b class="gmail_sendername">Holger Hoffstaette</b> &lt;<a href="mailto:holger@wizards.de">holger@wizards.de</a>&gt; wrote:<div><span class="gmail_quote"></span><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
<br>Here's a heads up for those of you who have the source handy to check.<br><br>Both JDK 1.5 and 1.6 have serious confirmed bugs that leak unreclaimable<br>memory and will bring *idle* servers down, e.g. during the night or over
<br>the weekend when load is low or nonexistent. For more information see<br><a href="http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6460501">http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6460501</a> and related.
<br><br>In a nutshell BlockingQueue.poll(duration, TimeUnit) will leak *when that<br>wait times out*; it will not leak when something is returned from the<br>queue, as is the case with uninterrupted non-timed polling.<br>
<br>The bug is confirmed and serious because it triggers extremely nasty GC<br>panic that has the potential to bring the whole machine down due to<br>excessive CPU spinning and unresponsiveness of the VM to external signals.
<br><br>I think it would be good if someone with the source would do a quick &quot;find<br>all references to method&quot; to see if and how Mina is affected by this. I<br>would not be surprised if this is the reason behind some reported leaks -
<br>polling with timeout is extremely useful for service scheduling in various<br>forms and generally preferrable to complete blocking.</blockquote><div><br>Wow, this is shocking.&nbsp; Even Doug Lea and his co-workers make a mistake! :)&nbsp; I think the reason why this bug is found so late is because most people doesn't specify the polling timeout like we didn't for MINA.
<br><br>Trustin</div></div>-- <br>what we call human nature is actually human habit<br>--<br><a href="http://gleamynode.net/">http://gleamynode.net/</a><br>--<br>PGP key fingerprints:<br>* E167 E6AF E73A CBCE EE41&nbsp;&nbsp;4A29 544D DE48 FE95 4E7E
<br>* B693 628E 6047 4F8F CFA4&nbsp;&nbsp;455E 1C62 A7DC 0255 ECA6

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