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

Apache proxy load balancing

Apache works as a proxy that re-directs 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.

For more information, see http://httpd.apache.org/docs/current/mod/mod_proxy.html.

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