3.15.2 Configuration where the load is balanced by using a redirector

This subsection describes the configuration where the redirector that is registered in the Web server balances the load when the access point component is either a servlet or JSP.

Organization of this subsection
(1) Features of the system configuration
(2) Required software and the processes to be invoked in the respective machines

(1) Features of the system configuration

You can use this configuration, when the access point of the application running on a J2EE server is a servlet or JSP. Distribute the load by the redirector that is registered in the Web server. Load balancing can be implemented by registering the target Application Server in the configuration file of the redirector.

The following figure shows an example configuration where the load is balanced by using a redirector:

Figure 3-67 Example configuration where the load is balanced by using a redirector

[Figure]

Note: For other legend items, see 3.2 Description of the system configuration.

Features
  • Scalability and availability of the servlet and JSP can be secured. You can prepare multiple Application Server instances and then distribute the access from the client by the redirector, and thus distribute the load.
  • The Web server where the redirector is registered has to be deployed on a machine that is different from the machine where the Application Server is deployed.
  • If an error occurs in a specific Application Server instance or if maintenance is required, system fall back is possible by stopping the access to the corresponding Application Server from the redirector.
    Hint
    The use of a load balancer enables highly efficient load balancing without applying any load on the machine where the Web server is running.
Flow of requests
Requests are sent from the Web browser to the servlets and JSPs, running on the J2EE server and acting as the access points, through the Web server. At this point, the redirector registered in the Web server distributes the requests to the J2EE server that is a constituent element of the load-balancing cluster, in a round robin format.

(2) Required software and the processes to be invoked in the respective machines

The required software and the processes to be invoked when balancing the load by using a redirector are the same as in the configuration in which the Web server and Application Server are deployed separately, from among the configurations that use a servlet and JSP as access points. See 3.15.1 Configuration with a Web server and Application Server deployed on different machines.