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Subject: Re: Tomcat 6 busy threads issue
From: Kobi Biton <kobi@comns.co.il>
To: Tomcat Users List <users@tomcat.apache.org>
In-Reply-To: <4D25FA96.3050602@christopherschultz.net>
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Date: Sat, 08 Jan 2011 18:36:41 +0200
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Christopher,
On Thu, 2011-01-06 at 12:23 -0500, Christopher Schultz wrote:
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> Kobi,
> 
> On 1/6/2011 12:14 PM, Kobi Biton wrote:
> > -Tomcat 6.0.22
> 
> Great. Any opportunities to upgrade? Your version was never released and
> is over a year old.
 - Yep I agree and I believe that I will upgrade soon.
> 
> > - yes they are load balanced simple Round Robin Linux LVS  , (LB
> > distributes the requests evenly)
> 
> So, you expect each server to serve 1/N of the incoming requests per
> unit time. Any session stickiness?
> 
> > - All the servers (But 1) had the following thread pool confguration
> > prior the change:
> >    
> >    MaxThreads=1000 , minSpareThread=25,maxSpateThreads=75
> > 
> > 1 server had:
> > 
> >   MaxThreads=300 , minSpareThread=25,maxSpateThreads=75
> 
> Okay, that will mean that the second server will handle, at most, 300
> simultaneous connections. Do you have any per-backend-server connection
> limits set at the load balancer?
> 
> > For some reason the server that had MaxThreads=300 report x2
> > threadCount / threadBusy Via JMX polling , only after changing its
> > maxThreads to 1000 the threadCount/threadBusy count was decreased x2 and
> > matched all the other servers
> 
> So, let's do an example so I can get my head around it:
> 
> N = 3
> 
> Server 1: maxThreads=1000, busy=100
> Server 2: maxThreads=1000, busy=100
> Server 3: maxThreads=300,  busy=200
> 
> Is that roughly what you observed?
- Yes 100% Right
>  Was that consistent over a long
> period of time?
- Yep consistent since tomcat start
>  Did you observe what kinds of requests were being served
> on server 3? If some of them were long-running, you may just be
> observing a natural build-up of work on a server that reliably gets 33%
> of incoming requests but has some older requests that are still processing.
> 
> > - Indeed busyThreads <= maxThreads
> 
> Good. If that weren't true, something would be terribly wrong :)
> 
> > Just trying to figure out why did the maxThreads was Impacting the
> > thread busy/count ...
> 
> I can't imagine why it would, other than putting a cap on the number of
> busy threads (because busyThreads <= maxThreads).
> 
> What kind of lb are you using?
Linux ipvsadm basically LVS
> 
> - -chris

Kobi.
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-- 
Kobi Biton
Com N S Ltd.

Mobile: +972 (54) 8017668


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