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From Jim Jagielski <>
Subject Re: Developer feedback on mod_balancer bug #57543
Date Thu, 26 Feb 2015 21:40:38 GMT
One of the big changes in mod_balancer between 2.2 and 2.4 is
the addition of real dynamic capability, adding and deleting
balancers as needed, in addition to changing their runtime
config. Because of the former, we need to "pad out" the shm
to allow for this growth (you can just add another entry
like you can with APR tables, for example). So you can
increase, or decrease, that padding w/ the BalancerGrowth

The other issue is whether or not balancers are "inherited"
by vhosts or not; if balancers are defined in the main server,
then depending on your config, they may, or may not, be replicated
in the vhosts, and due to how that inheritance happens, you may
be wasting space. Unfortunately, the default is the bloated
setup, since that was/is backwards compatible :(

Hope this helps!

> On Feb 26, 2015, at 1:22 AM, Federico Mennite <> wrote:
> Hi,
> a few days ago I've submitted the bugreport below
> I was pondering on removing some rust from my C programming skills and try to create
a patch for this issue. However I'd like to get some feedback from the developers who worked
on it.
> Questions:
> - Why weren't such a large number of semaphores and shared memory segments required for
mod_balancer to run in apacche 2.2?
> - am I right in stating that the current code in apache 2.4 seems to allocate a lot more
resources than really needed?
> - are my behavioral "conclusions" close enough to what the setup code of mod_balancer
is currently doing?
> Thanks for your help,
> Federico

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