For an article in a news paper, I'm benchmarking 5 different web servers (Apache2, Cherokee, Lighttpd, Monkey and Nginx).

The tests made consist of measuring the execution times as well as different parameters such as the number of request served per second, the amount of RAM, the CPU used, during a growing load of simultaneous clients (from 1 to 1.000 with a step of 10) each client sending 1.000.000 requets of a small fixed file, then of a medium fixed file, then a small dynamic content (hello.php) and finally a complex dynamic content (the computation of the reimbursment of a loan).

All the web servers are able to sustain such a load (up to 1.000 clients) but Apache2 which always stops to respond when the test reach 450 to 500 simultaneous clients.

My configuration is :

• CPU: AMD FX 8150 8 cores @ 4.2 GHz
• RAM: 32 Gb.
• SSD: 2 x Crucial 240 Gb SATA6
• OS: Ubuntu 12.04.3 64 bit
• WS: Apache 2.2.22

My Apache2 configuration is as follows:

/etc/apache2/apache2.conf

LockFile ${APACHE_LOCK_DIR}/accept.lock
PidFile ${APACHE_PID_FILE}
Timeout 30
KeepAlive On
MaxKeepAliveRequests 1000000
KeepAliveTimeout 2
ServerName "fnux.net"
<IfModule mpm_prefork_module>
  StartServers         16
  MinSpareServers      16
  MaxSpareServers      16
  ServerLimit        2048 
  MaxClients         1024
  MaxRequestsPerChild   0
</IfModule>
User ${APACHE_RUN_USER}
Group ${APACHE_RUN_GROUP}
AccessFileName .htaccess
<Files ~ "^\.ht">
  Order allow,deny
  Deny from all
  Satisfy all
</Files>
DefaultType None
HostnameLookups Off
ErrorLog ${APACHE_LOG_DIR}/error.log
LogLevel emerg
Include mods-enabled/*.load
Include mods-enabled/*.conf
Include httpd.conf
Include ports.conf
LogFormat "%v:%p %h %l %u %t \"%r\" %>s %O \"%{Referer}i\" \"%{User-Agent}i\"" vhost_combined
LogFormat "%h %l %u %t \"%r\" %>s %O \"%{Referer}i\" \"%{User-Agent}i\"" combined
LogFormat "%h %l %u %t \"%r\" %>s %O" common
LogFormat "%{Referer}i -> %U" referer
LogFormat "%{User-agent}i" agent
Include conf.d/
Include sites-enabled/

/etc/apache2/ports.conf

NameVirtualHost *:8180
Listen 8180
<IfModule mod_ssl.c>
  Listen 443
</IfModule>
<IfModule mod_gnutls.c>
  Listen 443
</IfModule>

/etc/apache2/mods-available

<IfModule mod_fastcgi.c>
   AddHandler php5-fcgi .php
   Action php5-fcgi /cgi-bin/php5.external
   <Location "/cgi-bin/php5.external">
     Order Deny,Allow
     Deny from All
     Allow from env=REDIRECT_STATUS
   </Location>
 </IfModule>

/etc/apache2/sites-available/default

<VirtualHost *:8180>
  ServerAdmin webmaster@localhost
  DocumentRoot /var/www/apache2
  <Directory />
    Options FollowSymLinks
    AllowOverride None
  </Directory>
  <Directory /var/www/>
    Options Indexes FollowSymLinks MultiViews
    AllowOverride None
    Order allow,deny
    allow from all
  </Directory>
  ScriptAlias /cgi-bin/ /usr/lib/cgi-bin/
  <Directory "/usr/lib/cgi-bin">
    AllowOverride None
    Options +ExecCGI -MultiViews +SymLinksIfOwnerMatch
    Order allow,deny
    Allow from all
  </Directory>
ErrorLog ${APACHE_LOG_DIR}/error.log
LogLevel emerg
#####   CustomLog ${APACHE_LOG_DIR}/access.log combined
Alias /doc/ "/usr/share/doc/"
  <Directory "/usr/share/doc/">
    Options Indexes MultiViews FollowSymLinks
    AllowOverride None
    Order deny,allow
    Deny from all
    Allow from 127.0.0.0/255.0.0.0 ::1/128
  </Directory>
  <IfModule mod_fastcgi.c>
    AddHandler php5-fcgi .php
    Action php5-fcgi /php5-fcgi
    Alias /php5-fcgi /usr/lib/cgi-bin/php5-fcgi
    FastCgiExternalServer /usr/lib/cgi-bin/php5-fcgi -host 127.0.0.1:9000 -pass-header Authorization
  </IfModule>
</VirtualHost>

/etc/security/limits.conf

* soft nofile 1000000
* hard nofile 1000000

So, I would trully appreciate your advice to setup Apache2 to make it able to sustain 1.000 simultaneous clients, if this is even possible.

TIA for your help. Cheers.