A Comprehensive Guide to IBM WebSphere Host Publisher Version 3.5

600 IBM WebSphere Host Publisher Version 3.5

19.4 Application considerations

When using the Host Publisher Studio to create applications for a cloned

environment, you will need to enable the WebSphere load balancing support.

Note: Host Publisher Studio provides an option to support WebSphere load

balancing so that HTTP session affinity will be established.

Configuration in Host Publisher Studio

In the Host Publisher Studio menu bar, select Options, then check the Support

WebSphere Load balancing option.

Figure 19-6 Enabling the WAS load balancing option in Host Publisher Studio

The following code will be added to your application page by Host Publisher

Studio when this option is used:

<%

HttpSession hp_session = request.getSession(true);

%>

Chapter 19. Cloning and Workload Management (WLM) 601

Integration Object chaining

If you are using WebSphere Application Server for cloning application servers

(JVMs) for load balancing, and you are using Integration Objects chaining in a

servlet or JSP, you must configure HTTP session affinity to ensure that the same

Web client (browser) returns to the JVM that originally established the host

connection.

HTTP session affinity requires WebSphere session persistence to share the

HTTP session object (which represents the connection between the Web client

and the Web server) across multiple application servers. To ensure HTTP

session affinity in a WAS cloned configuration, the HTTP session must be fully

established. The HTTP session is not fully established until the second HTTP

request is sent from the Web client to the Web server. One way to do this is to

check whether the HTTP session is a new session. If so, force a second HTTP

session request to flow between the Web client and the Web server, using the

sendRedirect method of the Java Servlet specification.

The following scenario is one example of how to ensure HTTP session affinity in

a WAS cloned configuration.

1. On all form pages, create an HTTP session object, if one has not already

been created. This prevents the loss of form data.

//-------------------------------------------------------------------------

//Establish session object which can be used by chained applications.

//This is necessary to prevent form POST action from changing to GET

//as the result of the sendRedirect()initiated by the jsp page containing

//the first chained bean.It prevents the loss of parameter,content and

//referer data.

HttpSession hp_session =request.getSession(true);

//-------------------------------------------------------------------------

2. To establish HTTP session affinity before the first Integration Object in a chain

is run, force the second HTTP request to flow back to the Web client for a new

HTTP session.

//-------------------------------------------------------------------------

//Establish session affinity to insure the execution of chained bean

application

//is performed on the same JVM,giving all IO's in chain access to the same

//connection.If this is the target of form page,the session will have

//been previously established and isNew()will return false.

HttpSession hp_session =request.getSession(true);

if (hp_session.isNew()){

String targetURL =request.getServletPath();

Note: The Host Publisher Server provides an option to support WebSphere

load balancing so that HTTP session affinity will be established.