users@grizzly.java.net

Re: do select spin on linux

From: Oleksiy Stashok <Oleksiy.Stashok_at_Sun.COM>
Date: Fri, 17 Apr 2009 14:21:50 +0200

>>
>>
>> Apr 16, 2009 9:29:22 PM com.sun.grizzly.Controller
>> handleSelectException
>> SEVERE: Selector was unexpectedly closed.
>> java.io.IOException: File exists
>> at sun.nio.ch.EPollArrayWrapper.epollCtl(Native Method)
>> at
>> sun
>> .nio
>> .ch.EPollArrayWrapper.updateRegistrations(EPollArrayWrapper.java:233)
>> at sun.nio.ch.EPollArrayWrapper.poll(EPollArrayWrapper.java:214)
>> at sun.nio.ch.EPollSelectorImpl.doSelect(EPollSelectorImpl.java:
>> 65)
>> at sun.nio.ch.SelectorImpl.lockAndDoSelect(SelectorImpl.java:69)
>> at sun.nio.ch.SelectorImpl.select(SelectorImpl.java:80)
>> at
>> com.sun.grizzly.TCPSelectorHandler.select(TCPSelectorHandler.java:
>> 528)
>> at com.sun.grizzly.Controller.doSelect(Controller.java:328)
>> at
>> com
>> .sun.grizzly.SelectorHandlerRunner.run(SelectorHandlerRunner.java:90)
>> at java.lang.Thread.run(Thread.java:619)
>>
>> Thanks for looking and for asking. I had to modify Controller.java
>> to print the stack trace in this log message. Until now I didn't
>> know I was getting the File exists exception, just as in the bug
>> report I quoted above.
> Thank you. I've fixed Controller code to show SEVERE exceptions
> stacktrace.
>
>
> Ok, so do you need me to file an issue report?
Yes, and if you have workaround - will appreciate if you can share it.

Thanks.

WBR,
Alexey.

>
>
> Thanks,
> John
>
>
>>
>>
>> Thanks,
>> John
>>
>>
>> Thanks.
>>
>> WBR,
>> Alexey.
>>
>>>
>>>
>>> Regards,
>>> John
>>>
>>>
>>>
>>> Thanks!
>>>
>>> -- Jeanfrancois
>>>
>>>
>>> John
>>>
>>>
>>>
>>> On Tue, Apr 14, 2009 at 10:14 AM, Jeanfrancois Arcand <Jeanfrancois.Arcand_at_sun.com
>>> <mailto:Jeanfrancois.Arcand_at_sun.com>> wrote:
>>>
>>> Salut,
>>>
>>> back online
>>>
>>>
>>> John Franey wrote:
>>>
>>> Jeanfrancois,
>>>
>>> Just a couple of clarifications:
>>>
>>> 1) Running from the command line needs the jar files too.
>>> Sorry
>>> I gave the impression that it was too easy. I think its
>>> easiest
>>> to run from IDE, especially since a debugger is needed. I
>>> hope
>>> that is ok.
>>>
>>>
>>> OK I will try to reproduce the issue but I usually don't use
>>> IDE (I
>>> use vim :-)).
>>>
>>>
>>>
>>>
>>> 2) Also, the BReceiver won't be idle during the rest sleeps.
>>> Sorry about that. Instead, once the exception occurs,
>>> simply
>>> kill the UDPSender process, then you will be sure the
>>> BReceiver
>>> is not receiving any new packets.
>>>
>>>
>>> OK. BTW I've talked to the NIO/JDK lead and nothing about
>>> spinning
>>> selector has been reported on jdk 4/5/6 so we might need to
>>> closely
>>> look at your code.
>>>
>>> Thanks
>>>
>>> -- Jeanfrancois
>>>
>>>
>>>
>>> Regards,
>>> John
>>>
>>>
>>>
>>> On Thu, Apr 9, 2009 at 2:31 PM, John Franey <jjfraney_at_gmail.com
>>> <mailto:jjfraney_at_gmail.com> <mailto:jjfraney_at_gmail.com
>>>
>>> <mailto:jjfraney_at_gmail.com>>> wrote:
>>>
>>> Jeanfrancois,
>>>
>>> I got lucky, here is a test case. (gmail didn't let me
>>> send
>>> it as
>>> zip, so its a jar).
>>>
>>> this is a maven project, I guess you can build and run.
>>>
>>> There are two main classes.
>>>
>>> A receiver, BReceiver, and a sender, UDPSender.
>>>
>>> I run these from eclipse. I guess your IDE will let
>>> your run
>>> them
>>> easily, but I guess from the command line something easy
>>> like:
>>> java -cp target/classes grizzlyproto/BReceiver would run.
>>>
>>> BReciever cycles a single udp port through many
>>> connections.
>>> UDPSender sends datagrams to that port at high rate.
>>>
>>> Periodically, BReceiver pauses at a time when there
>>> should be
>>> no cpu
>>> charges to that process. Not sure this helps, but the
>>> intention was
>>> that if the process is using cpu at this time, then the
>>> selector is
>>> spinning.
>>>
>>> Within a few moment, BReceiver will get an exception (I do
>>> not know
>>> if the exception is related to the problem). Then you
>>> can set
>>> breakpoint on Controller.doSelect's return from
>>> selectorHandler.select (at line 329) to inspect value of
>>> readyKeys. Its empty.
>>>
>>>
>>> Here are my system specificaitons (from ubuntu 8.10)
>>> Linux isidore 2.6.27-11-generic #1 SMP Thu Jan 29 19:28:32
>>> UTC 2009
>>> x86_64 GNU/Linux
>>>
>>>
>>> I get the same behavior on both of these:
>>>
>>> java version "1.6.0_12"
>>> Java(TM) SE Runtime Environment (build 1.6.0_12-b04)
>>> Java HotSpot(TM) 64-Bit Server VM (build 11.2-b01, mixed
>>> mode)
>>>
>>> and
>>>
>>> java version "1.6.0_03"
>>> Java(TM) SE Runtime Environment (build 1.6.0_03-b05)
>>> BEA JRockit(R) (build
>>> R27.5.0-110-94909-1.6.0_03-20080204-1558-linux-x86_64,
>>> compiled mode)
>>>
>>>
>>> Regards,
>>> John
>>>
>>>
>>>
>>> On Thu, Apr 9, 2009 at 2:00 PM, John Franey
>>> <jjfraney_at_gmail.com <mailto:jjfraney_at_gmail.com>
>>> <mailto:jjfraney_at_gmail.com <mailto:jjfraney_at_gmail.com>>>
>>> wrote:
>>>
>>> Thanks.
>>>
>>>
>>> On Thu, Apr 9, 2009 at 1:02 PM, Jeanfrancois Arcand
>>> <Jeanfrancois.Arcand_at_sun.com
>>> <mailto:Jeanfrancois.Arcand_at_sun.com>
>>> <mailto:Jeanfrancois.Arcand_at_sun.com
>>> <mailto:Jeanfrancois.Arcand_at_sun.com>>> wrote:
>>>
>>> Salut,
>>>
>>>
>>> John Franey wrote:
>>>
>>> Hi,
>>>
>>> I'm running stress tests on linux. At some
>>> point, cpu
>>> utilization goes high. I've verified using
>>> the
>>> debugger
>>> that Controller.doSelect gets zero keys back
>>> from
>>> handler's select.
>>>
>>>
>>> Yes this is an issue I've reported awhile ago to
>>> the JDK
>>> team. This sounds like bugparade 6403933
>>>
>>> http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6403933
>>>
>>> A connection is reset causes the file descriptor
>>> to be
>>> selected with events POLLHUP and POLLERR but
>>> unless
>>> there is
>>> data waiting to be read then channel will not be
>>> selected.
>>> It's a awkward problem.
>>>
>>> This has been fixed in JDK 7 build 50 and will be
>>> included
>>> in JDK 6u16.
>>>
>>>
>>> The last statement in the evaluation of this bug nails
>>> it, and
>>> the load pattern described in this bug matches
>>> mine: http://bugs.sun.com/view_bug.do?bug_id=6693490
>>>
>>> It sounds like the same root cause?
>>>
>>>
>>>
>>> Google search led me to this page at apache
>>> mina jira
>>> DIRMINA-678
>>> <https://issues.apache.org/jira/browse/DIRMINA-678
>>> >.
>>>
>>> Please see especially, this comment from
>>> Emannual
>>> Lecharmy (31/Mar/09 03:23 PM)
>>> <https://issues.apache.org/jira/browse/DIRMINA-678?focusedCommentId=12696711&page=com.atlassian.jira.plugin.system.issuetabpanels%3Acomment-tabpanel
>>> #action_12696711
>>> <https://issues.apache.org/jira/browse/DIRMINA-678?focusedCommentId=12696711&page=com.atlassian.jira.plugin.system.issuetabpanels%3Acomment-tabpanel#action_12696711
>>> >
>>> <https://issues.apache.org/jira/browse/DIRMINA-678?focusedCommentId=12696711&page=com.atlassian.jira.plugin.system.issuetabpanels%3Acomment-tabpanel
>>> #action_12696711
>>> <https://issues.apache.org/jira/browse/DIRMINA-678?focusedCommentId=12696711&page=com.atlassian.jira.plugin.system.issuetabpanels%3Acomment-tabpanel#action_12696711
>>> >>>.
>>>
>>>
>>> So, I'm looking for this 'beautiful hack' in
>>> the
>>> Controller source code for 1.9.11 and am not
>>> seeing it.
>>> I think maybe I'm blind :) or the hack is
>>> in grizzly
>>> 2.0? If its in 2.0, do you think I can make
>>> it
>>> fit into
>>> 1.9.11? Or do you advise I try my
>>> application on
>>> 2.0 trunk?
>>>
>>>
>>> I didn't put the hack there (just for Comet) as I
>>> never saw
>>> it on the Controller. Can you share a test case?
>>>
>>>
>>> I don't have a test case and am working on one. I
>>> would be
>>> surprised if I can get it to happen without a lot of
>>> work.
>>>
>>> Is there a code sample from comet that has this hack
>>> in it to
>>> see if I can make the same change for my app?
>>>
>>> Thanks
>>>
>>> -- Jeanfrancois
>>>
>>>
>>>
>>> Thanks,
>>> John
>>>
>>>
>>>
>>>
>>>
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>>> .jar
>>> >
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>>
>>
>
>