Bug#364777: Default configuration for SSLSessionCache in trouble under high load

[Yves Martin <yves.martin@elca.ch>]

Package: apache2-common
Version: 2.0.54-5

 We have set the following worker configuration to be able to process large
 number of requests on a https proxy server:

<IfModule worker.c>
StartServers         2
MaxClients          1024
MinSpareThreads     25
MaxSpareThreads     75
ThreadsPerChild     64
ThreadLimit         128
ServerLimit         32
MaxRequestsPerChild  0
</IfModule>

 under really high load... servers got into trouble.
 The following error log is then generated:

[error] (120013)APR does not understand this error code: Cannot open
SSLSessionCache DBM file `/var/run/apache2/ssl_scache' for reading (fetch)

 and then the disk IO comes to limit (check with vmstat).

 The following default configuration in /etc/apache2/mods-available/ssl.conf

SSLSessionCache        shmcb:/var/run/apache2/ssl_scache(512000)

 instead of 

SSLSessionCache         dbm:/var/run/apache2/ssl_scache

 would have help us to avoid downtime on our servers - in fact the time to
 understand why the servers cannot server requests and change this parameter

 I'm running Debian Sarge 3.1 - up-to-date - with kernel-image-2.4.27-2-686-smp
$uname -a
Linux elbe 2.4.27-2-686-smp #1 SMP Wed Aug 17 10:05:21 UTC 2005 i686 GNU/Linux

 and libc6 2.3.2.ds1-22


 Hope this may help other administrators to avoid such troubles.

-- 
Yves Martin