Configuring an Apache HTTP Server to implement load balancing involves updating the apache_install_dir/conf/httpd.conf file to:

  • Specify the proxy modules to load.
  • Reference the PAS for OpenEdge instances.
  • Enable or disable sticky sessions.
Note: In addition to configuring Apache, you must configure each PAS for OpenEdge instance. See Configure PAS for OpenEdge instances for proxy load balancing.

Loading proxy modules

Proxy modules set up the Apache web server as a proxy to handle requests to multiple PAS for OpenEdge instances. The modules are loaded by uncommenting LoadModule directives in the httpd.conf file of the Apache web server. The LoadModule directives include:

  • LoadModule proxy_module modules/mod_proxy.so
  • LoadModule proxy_connect_module modules/mod_proxy_connect.so
  • LoadModule proxy_http_module modules/mod_proxy_http.so
  • LoadModule slotmem_shm_module modules/mod_slotmem_shm.so
  • LoadModule bmethod_byrequests_module modules/mod_lbmethod_byrequests.so
Note: Depending on which version of Apache you are using, there may be additional modules required. See the Apache web site (http://httpd.apache.org/) for documentation on your version of the Apache server.

Referencing instances and configuring session types

Update Apache’s httpd.conf file to include a load balancer section that lists the PAS for OpenEdge instances in the load balancing group. This can be configured two different ways:

  • Session free—Any request can be sent to any PAS for OpenEdge instance.
  • Sticky session—After a session is started, all requests return to the same PAS for OpenEdge instance until the session is terminated.
    Note: Sticky sessions are required for the APSV transport, but not for WEB, REST, or SOAP.

If there is no need for client requests to return the the same PAS for OpenEdge instance (that is, maintaining server-side context is not required), your entries in httpd.conf should resemble the following example:

#Load balancer Proxy settings (session free)
      <Proxy "balancer://mylbgroup">
      BalancerMember "http://172.16.21.39:11600"
      BalancerMember "http://172.16.21.39:11610"
      BalancerMember "http://172.16.21.39:11620"
      </Proxy>
      ProxyPass "/test" "balancer://mylbgroup"
      ProxyPassReverse "/test" "balancer://mylbgroup"

Notice that, in the example, the instances where Apache can refer requests are grouped as //mylbgroup, and the URL of these instances (the BalancerMember properties) are specified.

If it is necessary for sequential requests to go to the same instance, as they are for the APSV transport, enable sticky sessions by adding a route property to BalancerMember and by enabling JSESSIONID cookies, for example: 

#Load balancer Proxy settings (sticky sessions)
      <Proxy "balancer://mylbgroup">
      BalancerMember "http://172.16.21.39:11600" route=oepas1
      BalancerMember "http://172.16.21.39:11610" route=oepas2
      BalancerMember "http://172.16.21.39:11620" route=oepas3
      </Proxy>
      ProxyPass "/test" "balancer://mylbgroup" stickysession=JSESSIONID|jsessionid nofailover=On
      ProxyPassReverse "/test" "balancer://mylbgroup"

In the example, notice that:

  • The route property must match the jvmroute value in the server.xml file of the instance.
  • The stickysession property enables the JSESSIONID cookie, which is the mechanism used to identify the session.

For more information about session configurations in the httpd.conf file, see the Apache web site (http://httpd.apache.org/) for documentation about your version of the Apache server.