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From Zisis Lianas <>
Subject Re: httpd 2.4.2 - mod_proxy id name not unique
Date Tue, 11 Sep 2012 14:01:33 GMT
Hi Jim,

what do you think about the suggested directives of
"ProxyConfigIdPrefix" and "BalancerSlotmemDir"?
(any other way to solve this problem is also welcome)

Today I just ran into the same problem with httpd-2.4.3.
The apache config/logs directory is shared (NFS) on two
servers - when trying to restart both apache instances
at same time, the last one throws an error:
  [proxy_balancer:debug] mod_proxy_balancer.c(760): AH01178: Doing balancers create: 544,1
  [slotmem_shm:debug] mod_slotmem_shm.c(300): AH02300: create /apache/logs/slotmem-shm-sbf751527.shm:
  [proxy_balancer:emerg] (17)File exists: AH01179: balancer slotmem_create failed

When I restart this instance when the first one is up,
the restart is successful.


----- Original Message -----
From: "Jim Jagielski" <>
Sent: Tuesday, May 1, 2012 8:43:46 PM
Subject: Re: httpd 2.4.2 - mod_proxy id name not unique

Let me look into that... iirc, it was due to us wanting to
be able to persist data between restarts and using the time
as part of the id prevented that. But I could be mis-remembering.

On Apr 30, 2012, at 7:50 AM, Zisis Lianas wrote:

> hi,
> when mod_proxy currently is generating his "id", the name
> of this id is not very unique. So if you have a shared config/
> logs dir for more instances, the slotmem-shm files generated in
> DefaultRuntimeDir are the same. Bit unlucky if working with shared
> file systems.
> In httpd-2.4.2/modules/proxy/mod_proxy.c line 1146 I can see
> the following code:
> #if 0
>    id = ap_proxy_hashfunc(apr_psprintf(p, "%pp-%" APR_TIME_T_FMT, ps, apr_time_now()),
> #else
>    id = ap_proxy_hashfunc(apr_psprintf(p, "%pp", ps), PROXY_HASHFUNC_DEFAULT);
> #endif
> Primarily checked in with
> If activating the first ap_proxy_hashfunc call, the generated names
> seem to be unique. Is there any reason this code is not used? Maybe
> we can set the "timed" version as default?
> best regards,
> Zisis

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