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From Madhuri Patwardhan <madhuri_patward...@yahoo.com>
Subject Re: what exactly happens when timeouts are set and tomcat has outofmemory errors.
Date Tue, 04 Aug 2009 11:24:44 GMT

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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