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From "Bill Barker" <wbar...@wilshire.com>
Subject Re: mod_jk round robin problem & stateless session beans
Date Tue, 15 Jul 2003 05:55:02 GMT
This is a pretty good description of what goes on, and it results in the
highly skewed distributions that you are seeing.  I had thought that if you
are using Apache-2 with the 'worker' MPM, that you should get a better
distribution (but haven't tried it myself).  With Apache-1.3.x or Apache-2
with the 'pre-fork' MPM this is as good as it gets at the moment (since the
'pre-forked' processes don't talk to each other).  In theory, it should be a
relatively easy fix in Jk2 to get 'pre-fork' working, but AFAIK, it hasn't
been implemented yet.

"NormW" <normw@bocnet.com.au> wrote in message
news:019701c34a55$643d7250$b441ca0a@nwinc.org.au...
> Good morning Simon.
> 'RoundRobin' is less likely the more Tomcat's you add I suspect. The
> balanced worker program always searches for a new worker by starting
> pointers from 1 rather than the last successful worker used, (AFAICT), and
> if a worker is free for the task it makes for muddy water indeed if you
> bypass it in the hope of finding something better... You need to remember
> which one was used 'last', which is a 'state' not remembered if/once
session
> ID's are used (which go to the worker that handled it the last time). If
you
> think about 'balancing' it is 'mindgame' to decide how a 'load' might be
> distributed... based on session counts? based on request handling time?
and
> what 'integration' period would you use? ... and then there are
preferences
> based on load, server grunt, network traffic, background tasks...  at the
> end of the day, the idea is to handle user requests, so if they're getting
> processed in a 'timely' manner perhaps you can put the 'unused' Tomcat's
> behind another Apache? ... or start a new thread here on how balancing
might
> be better handled in different situations...
>
> Another 'possible' might be to add more balance workers and split your
url's
> to these, in turn connected to more ajp13 workers using some of the
Tomcat's
> currently sitting idle.
> Norm
>
>
> ----- Original Message -----
> From: "Simon Pabst" <simon.pabst@web.de>
> To: <tomcat-user@jakarta.apache.org>
> Sent: Tuesday, July 15, 2003 7:17 AM
> Subject: mod_jk round robin problem & stateless session beans
>
>
> > We have the following setup:
> > One Apache with HTTPS/SSL with mod_jk (one load balancer, sticky
sessions
> > on) in front
> > Eight Tomcats in back
> >
> > Round Robin doesn't work, but instead the Users are distributed on the
> > Tomcats like this:
> >
> > Tomcat No.| User Count (approx. daily)
> > T1 70
> > T2 30
> > T3 15
> > T4 6
> > T5 1
> > T6 0
> > T7 0
> > T8 0
> >
> > This occurs both with Apache1.3.27/mod_jk1.2.x and
Apache2.0.45/mod_jk2.x
> > (mod_jk 1 and 2 built from source of
jakarta-tomcat-connectors-4.1.24-src
> > and later also of tomcat-connectors-1.1M1-src).
> >
> > Anyone ever experienced something similar or has any insight in this?
> >
> > According to the application developer the application is using
stateless
> > session beans.
> > (Since i'm just a stupid server admin and no Java Programmer i don't
> really
> > now what that is :-)
> >
> > I tested the Load Balancing with the Tomcat SessionExample and round
robin
> > seemed to work fine.
> > If i switch of sticky session round robin also works fine, but not the
> > application :-)
> >
> > Do stateless session beans even work with mod_jk's sticky session stuff?
> > (in this discussion
> > http://www.theserverside.com/discussion/thread.jsp?thread_id=409
> > somebody said:
> > "if the application stores the stateless session bean in the
httpsession,
> > the application risks having all of the workload to only one of the
nodes
> > in the cluster")
> >
> > If anyone knows how sticky sessions of mod_jk(2) work, please enlighten
me
> :-)
> > Is it IP based in any way, are Cookies involved or JSESSIONID or
anything
> else?
> > Could it be a problem that all Tomcats are on the same machine? (i
tested
> > this with pseudo network addresses 127.0.0.1-8 for each Tomcat too, but
> > didn't help either)
> > Could HTTPS cause any troubles for this?
> >
> >
> >
> > ---------------------------------------------------------------------
> > To unsubscribe, e-mail: tomcat-user-unsubscribe@jakarta.apache.org
> > For additional commands, e-mail: tomcat-user-help@jakarta.apache.org
> >
> >




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