This section explains how to set up the Apache server with the mod_proxy_balancer module for load balancing. For more information on the mod_proxy_balancer, see http://httpd.apache.org/docs/2.2/mod/mod_proxy_balancer.html.

1. In the APACHE_HOME\conf\httpd.conf file, enable the mod_proxy, mod_proxy_balancer, and mod_proxy_ajp modules by removing the following comment tags:

   #LoadModule proxy_module modules/mod_proxy.so
   #LoadModule proxy_ajp_module modules/mod_proxy_ajp.so
   #LoadModule proxy_balancer_module modules/mod_proxy_balancer.so
   

2. Enter the following. For this sample cluster, the load balancer (on the localhost or Storefront Server 1) has an IP address of 10.10.90.54. The other three storefront servers have IP addresses 10.10.90.51, 10.10.90.52, and 10.10.90.53.

   <VirtualHost 10.10.90.54:80>
   
           ServerName 10.10.90.54
   
           # ProxyPreserveHost On
           RequestHeader set Host mars.elasticpath.net
   
           <Proxy balancer://tomcatservers>
                   BalancerMember ajp://localhost:9009 route=node1 loadfactor=90
                   BalancerMember ajp://10.10.90.51:9009 route=node2 loadfactor=100
                   BalancerMember ajp://10.10.90.52:9009 route=node3 loadfactor=100
                   BalancerMember ajp://10.10.90.53:9009 route=node4 loadfactor=100
           </Proxy>
   
           ProxyPass /storefront balancer://tomcatservers/storefront stickysession=JSESSIONID nofailover=Off
           ProxyPass /server-status !
   
   </VirtualHost>
   
   <VirtualHost 10.10.90.54:443>
   
           ServerName 10.10.90.54
           LogLevel warn
           #CustomLog logs/ssl_request_log "%t %h %{SSL_PROTOCOL}x %{SSL_CIPHER}x \"%r\" %b"
           LogFormat "%h %l %u %t \"%r\" %>s %b" common
           CustomLog logs/ssl_access_log common
           ErrorLog logs/ssl_error_log
   
           #   SSL Engine Switch:
           #   Enable/Disable SSL for this virtual host.
           SSLEngine on
           SSLCipherSuite ALL:!ADH:!EXPORT56:RC4+RSA:+HIGH:+MEDIUM:+LOW:+SSLv2:+EXP:+eNULL
           SSLCertificateFile "/commerce-legacy/usr/local/apache2/conf/server.crt"
           SSLCertificateKeyFile "/commerce-legacy/usr/local/apache2/conf/server.key"
   
           #DocumentRoot    "/commerce-legacy/var/www/html/one"
   
           # ProxyPreserveHost On
           RequestHeader set HOST mars.elasticpath.net
   
           SetEnvIf User-Agent ".*MSIE.*" nokeepalive ssl-unclean-shutdown downgrade-1.0 force-response-1.0
   
           <Proxy balancer://tomcatservers-ssl>
                   BalancerMember ajp://localhost:9010 route=node1 loadfactor=90
                   BalancerMember ajp://10.10.90.51:9010 route=node2 loadfactor=100
                   BalancerMember ajp://10.10.90.52:9010 route=node3 loadfactor=100
                   BalancerMember ajp://10.10.90.53:9010 route=node4 loadfactor=100
           </Proxy>
   
           ProxyPass /storefront balancer://tomcatservers-ssl/storefront stickysession=JSESSIONID nofailover=off
   
   </VirtualHost>
   

3. Note the following characteristics of the Proxy balancer element for the non-secure port 80 connector (code snippet below):

    
   ...
           <Proxy balancer://tomcatservers>
                   BalancerMember ajp://localhost:9009 route=node1 loadfactor=90
                   BalancerMember ajp://10.10.90.51:9009 route=node2 loadfactor=100
                   BalancerMember ajp://10.10.90.52:9009 route=node3 loadfactor=100
                   BalancerMember ajp://10.10.90.53:9009 route=node4 loadfactor=100
           </Proxy>
   
           ProxyPass /storefront balancer://tomcatservers/storefront stickysession=JSESSIONID nofailover=Off
           ProxyPass /server-status !
   ... 
   

   • The load balancer has four storefronts, including one on the localhost. Each machine has AJP port 9009 open and an even load factor except the localhost, which has a slightly lower load factor to accommodate the Apache workload.
   • The directive ProxyPass /storefront balancer://tomcatservers/storefront instructs ProxyPass to allow /storefront requests to pass to the balancer's /storefront. The stickysession parameter specifies the cookie to attach to each storefront node, so that requests will all return to the same node.
   • The route parameter is the name for a node's jvmRoute within the server.xml file. This allows Apache and the application server to identify which requests go to which node. Without this parameter (or the stickysession parameter), the user's session may bounce between storefront nodes and result in unexpected behavior.
4. To set the jvmRoute in the server.xml file, look for the following comment:

    
   <!-- You should set jvmRoute to support load-balancing via AJP ie :
    <Engine name="Catalina" defaultHost="localhost" jvmRoute="node1">         
   -->    
   

   Remove the comment tags and make the jvmRoute and route parameters equal.
5. Repeat step 3 for the secure connectors on AJP port 9010.
6. Restart the Apache server. It will load balance to a specific node in the cluster and stay on that node for subsequent requests.