Resource Management of Multiple Virtual Web Servers

Single machines are often used to host multiple virtual web servers in a consolidated fashion. In this case, multiple instances of the httpd web server process exist, and there is far greater opportunity to exploit resource control through Solaris Resource Manager.

It is possible to run each web server as a different UNIX UID by setting a parameter in the web server configuration file. This effectively attatches each web server to a different lnode in the Solaris Resource Manager hierarchy.

For example, the Sun WebServer^TM has the following parameters in the configuration file /etc/http/httpd.conf:

# Server parameters
 server  {
   server_root                   "/var/http/"
   server_user                   "webserver1"
   mime_file                     "/etc/http/mime.types"
   mime_default_type             text/nlain
   acl_enable                    "yes"
   acl_file                      "/etc/http/access.acl"
   acl_delegate_depth            3
   cache_enable                  "yes"
   cache_small_file_cache_size   8                       # megabytes
   cache_large_file_cache_size   256                     # megabytes
   cache_max_file_size           1                       # megabytes
   cache_verification_time       10                      # seconds
   comment                       "Sun WebServer Default Configuration"

   # The following are the server wide aliases

   map   /cgi-bin/               /var/http/cgi-bin/              cgi
   map   /sws-icons/             /var/http/demo/sws-icons/
   map   /admin/                 /usr/http/admin/

 # To enable viewing of server stats via command line,
 # uncomment the following line
   map   /sws-stats              dummy                           stats
 }

By configuring each web server to run as a different UNIX UID, you can set different limits on each web server. This is particularly useful for both control and accounting for resource usage on a machine hosting many web servers.

In this case, you can make use of many or all of the Solaris Resource Manager resource controls and limits:

Shares [cpu.shares]

The cpu.shares can be used to proportionally allocate resources to the different web servers.

Mem limit [memory.limit]

The memory.limit can be used to limit the amount of virtual memory that the web server can use, which will prevent any one web server from causing another to fail due to memory allocation.

Proc mem limit [memory.plimit]

The per-process memory limit can be used to limit the amount of virtual memory a single cgi-bin process can use, which will stop any cgi-bin process from bringing down its respective web server.

Process limit [process.limit]

The maximum total number of processes allowed to attach to a web server can effectively limit the number of concurrent cgi-bin processes.