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From Jim Jagielski <>
Subject Re: [users@httpd] Apache 2.4 create a huge amount of shared memory segments
Date Tue, 23 Dec 2014 13:52:56 GMT
If migrating to 2.4, I would suggest using the method Yann describes
and have each balancer defined in its own vhost section. This is
because it is most likely that inheriting balancers will be
deprecated/removed in later versions of httpd, simply because
(1) it doesn't make sense and (2) causes the kinds of issues
you see.

I would recommend using mod_macro to help out with your migration;
you could create a macro Vhost definition...

> On Dec 19, 2014, at 10:49 AM, Sylvain Goulmy <> wrote:
> Yann,
> I did some additionnal tests with the BalancerInherit directive. If I add the directive
"BalancerInherit Off" in the main section I still have the issue (shm saturation) if the number
of virtual hosts/balancers is too important. With a single virtual host then I can access
correctly to the application whereas I shouldn't be able to ... In other words, the directive
seems to have no effect. Anyway if it worked correctly i couldn't have accessed to my application
anymore, so i guess it doesn't deserve to spend more time on this question.
> I also did some test with the balancer definition inside the virtual host : I confirm
that this configuration is ok. Unfortunately for me, this choice introduces significant change
on my apache 2.2 configuration and adds a lot of complexity in my migration process. I also
lose some functionnality like an global overview of my balancer states via a single URL. 
> So before considering this option, as far as you know, do you think there is definitely
no other options available.
> Regards.
> Sylvain
> On Fri, Dec 19, 2014 at 2:06 PM, Yann Ylavic <> wrote:
> Hi Sylvain,
> On Fri, Dec 19, 2014 at 11:04 AM, Sylvain Goulmy <> wrote:
> >
> > My configuration is currently defining 338 virtual hosts and 169 proxy
> > balancers.
> >
> > The balancers are defined in the main section. Each virtual host refers only
> > one balancer.
> >
> > Here what i notice :
> > - Apache creates one shm for each balancer
> > - Each virtual hosts creates one shm for each balancer even if it doesn't
> > refer it...
> in 2.4, each vhost's balancer needs it own SHM plus as much SHMs as
> the balancer's members (the dynamic balancer-manager manages per
> vhost).
> By declaring all the balancers in the main config (and using
> "BalancerInherit on" to make them *all* available in *all* the
> vhosts), you multiply that number by the number of balancers and the
> number of of vhosts...
> >
> > Am i missing a directive that could avoid that behaviour or do i have to
> > redesign my all configuration by moving each balancer definition at the
> > virtual host level ?
> You can't set "BalancerInherit off" since the "main" balancers won't
> be usable in the vhosts anymore.
> Since moreover "each virtual host refers only one balancer" in your
> configuration, you'd better declare each balancer in the corresponding
> vhost, and see that no more shared-memory than needed will be created
> (depending on the number of balancer members used by each vhost).
> Regards,
> Yann.
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