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From Anantha Padmanabha <anantha.padmana...@bankbazaar.com>
Subject Re: what exactly happens when timeouts are set and tomcat has outofmemory errors.
Date Wed, 05 Aug 2009 06:07:10 GMT
Madhuri,

Its better to use max_reply_timeouts also in config so that LB does not mark
a worker as 'down' once in a while.
We dont use socket_connect_timeout and similar config you are mentioning had
worked fine while we did OutOfMemory testing as far as I remember.

If someone is not looking at why OOM is happening, I suggest you to give
more focus on that now before config changes

Thanks
Anantha

On Tue, Aug 4, 2009 at 4:54 PM, Madhuri Patwardhan <
madhuri_patwardhan@yahoo.com> wrote:

>
> Thanks for the reply.
>
> Even after reading documents I have some doubts.
>
> 1] How is a particular tomcat instance marked to "ERR" state?
> This is what I understand. If apache is not able to connect to that tomcat
> instance port ( typically when tomcat is not running) OR if it does not
> receive reply from the tomcat instance. The second part is were I am not
> very clear. If reply_timeout is not set then it waits indefinitely for the
> answer then how does it mark it in state "ERR". If reply_timeout is set then
> it will wait for that time for no. of retries and then mark it in state ERR.
> Is there any other way a instance would get marked to state ERR?
>
> 2] Once instance is marked to state ERR then how does recovery options
> affect it?
> As per the document: "Recovery options influence, how we should handle
> retries, in case we detect a problem with Tomcat. How often we will retry is
> controlled by the attribute retries."
> So, if for example I have recovery options set to 3 how would it work? If I
> have set it to 7 how would it work?
>
> I am trying to understand the details of all this so that I can get to the
> bottom of the problem that I am facing. The problem that I am having is
> after setting these timeouts I am seeing worse performance from the website
> There are many website access errors reported.
> Earlier the following was not set and now I have set ping_mode=A,
> reply_timeout=60000, socket_connect_timeout=5000 and recovery_options=3.
>
> Thanks,
> Madhuri
>
> --- On Tue, 8/4/09, Mark Thomas <markt@apache.org> wrote:
>
> > From: Mark Thomas <markt@apache.org>
> > Subject: Re: what exactly happens when timeouts are set and tomcat has
> outofmemory errors.
> > To: "Tomcat Users List" <users@tomcat.apache.org>
> > Date: Tuesday, August 4, 2009, 5:05 AM
> > Madhuri Patwardhan wrote:
> >
> > > Do you know anything about recovery options?
> >
> > No. You could try reading the docs and/or the source code.
> >
> > Mark
> > >
> > > Thanks,
> > > Madhuri
> > >
> > > --- On Mon, 8/3/09, Mark Thomas <markt@apache.org>
> > wrote:
> > >
> > >> From: Mark Thomas <markt@apache.org>
> > >> Subject: Re: what exactly happens when timeouts
> > are set and tomcat has outofmemory errors.
> > >> To: "Tomcat Users List" <users@tomcat.apache.org>
> > >> Date: Monday, August 3, 2009, 6:49 PM
> > >> Madhuri Patwardhan wrote:
> > >>> Hi,
> > >>>
> > >>> Can somebody go over the details of what
> > exactly
> > >> happens when tomcat instance has outOfmemory
> > errors and
> > >> there are following timeouts set in a loadbalancer
> > worker
> > >> config.
> > >>> This is my understanding.
> > >>>
> > >>> ping_mode=A, ping_timeout=10000,
> > reply_timeout=60000
> > >> and recorver_options=3
> > >>> If the timeouts are set as above then
> > CPing/Cpong test
> > >> for connect and prepost will work. When a new real
> > request
> > >> is sent to this tomcat instance, it should hit
> > reply_timeout
> > >> because it has outofmemory errors.
> > >>
> > >> That depends on the state of the JVM. It might
> > appear to
> > >> work normally,
> > >> it might fail to respond at all. Once on OOM has
> > occurred
> > >> Tomcat has to
> > >> be assumed to be in an unknown state and should
> > be
> > >> restarted. I have
> > >> seen Tomcat instances apparently recover from an
> > OOM. It
> > >> all depends why
> > >> the OOM occurred and what Tomcat was doing at the
> > time.
> > >>
> > >>> Then depending on no. of retries set (it is
> > default,
> > >> for me so 2), this instance will be tried once
> > again. Second
> > >> time also it should not get reply within
> > reply_timeout and
> > >> at that point it should be marked in "ERR" state.
> >
> > >>> However, I don't see that. I don't see it
> > being marked
> > >> in "ERR" state. The state is still "OK" inspite of
> > this
> > >> tomcat instance having outofmemory errors. Could
> > somebody
> > >> explain what am I missing?
> > >>
> > >> In short, you are incorrectly assuming that once
> > an OOM has
> > >> occurred
> > >> Tomcat will no longer respond to requests.
> > >>
> > >> Mark
> > >>
> > >>
> > >>
> > >>
> > >>
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> > >>
> > >>
> > >
> > >
> > >
> > >
> > >
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> > >
> >
> >
> >
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> >
> >
>
>
>
>
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>

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