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From "Bill Barker" <>
Subject Re: Production server tuning
Date Thu, 31 Jul 2003 07:45:27 GMT

"David Rees" <> wrote in message
> Bill Barker wrote:
> > "Antonio Fiol Bonnín" <> wrote:
> >> However, I am worried about what you say about Apache 2.0.x and the
> >> 'worker' MPM. Could you please tell me about the real-world
> >> inconveniences of having 3/4 Apache 1.3.X with 2/3 tomcats behind?
> >
> > The mod_jk loadbalancer doesn't work well with pre-fork (including
> > Apache 1.3.x on *nix systems).  Since your not using the mod_jk
> > loadbalancer, it shouldn't matter if you are using 1.3.x or 2.0.x.
> I'm curious, what are the issues with loadbalancing in mod_jk with a
> pre-forking Apache?

Basically it comes down to the fact that the children don't talk to one
another, so each one has its own idea of the relative loads.  This usually
results in a distribution (for the two-Tomcat case) somewhere between 70-30
and 80-20 (although people on this list have reported even more skewed
distributions).  It should get even more skewed as you increase the number
of Tomcats.

mod_jk2 already has the scoreboard (aka shm) in place to allow for the
children to coordinate this, but at the moment isn't using it for
loadbalancing (and so, is just as broken as mod_jk).  I can't add much more
except that patches are always welcome ;-)

> -Dave

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