With Apache proxy host load balancing, an Apache HTTP Server (also known as Apache) directs requests to a particular PAS for OpenEdge instance. The following figure illustrates this load balancing configuration.

Apache proxy load balancing

Apache works as a proxy re-directing HTTP requests to a URL that is unique to each instance. This method requires no configuration of the PAS for OpenEdge instance, all of the load balancing is done by the Apache server. The available PAS for OpenEdge instances are defined in an apache_install_dir/conf/httpd.conf file.

See also: http://httpd.apache.org/docs/current/mod/mod_proxy.html

Note: The disadvantage in this type of load balancing is the Apache server does not monitor the running status of instances. If an instance crashes or is otherwise unavailable, the Apache load balancer continues to try to send requests to the unavailable instance and requests will be lost. Compare with Tomcat load balancing, where the running status of instances is monitored.