3.6 Using NWBC with a Load Balancer

Use

If a load balancer is available within the network, it can be used directly with NWBC. Instead of configuring a direct URL on a specific application server, change the URL that NWBC is configured to, to use the load balancer. On startup, NWBC triggers a first HTTP request to the load balancer, which then redirects to an application server. For the duration of the NWBC session, the load balancer communicates only with this specific application server. All applications that are started run on the assigned application server. (This is similar to a typical SAP GUI session that stays on the same assigned application server and starts all new windows on the same server.)

In NWBC for Desktop, navigation data is cached in an ABAP system (SAP NetWeaver Application Server ABAP), and not on a specific application server. Therefore, if the load balancer assigns a different application server the next time NWBC for Desktop is started, the cached data are not invalidated.

Recommendation

We highly recommended that you use SAP Web Dispatcher as a load balancer, since it contains key information about HTTP traffic that can be used to route all subsequent HTTP requests more effectively to the same application server.

The following figure shows how to configure the load balancer:

Load balancer example

By default, transaction NWBC starts NWBC for HTML or the ~launch page on the same AS ABAP application server. However, transaction NWBC also includes all available information about an external Web Dispatcher, or message server used as load balancer if configured in the HTTPURLLOC table. In the HTTPURLLOC table, configure an entry for application = /NWBC/* to influence the URL generation of NWBC. By consequence, the startup URL is changed to reference the configured load balancer directly.

The following figure shows an example of the HTTPURLLOC table:

Example entry in table HTTPURLLOC

Note

You can also use load balancing settings of the SAP GUI if you enter the corresponding system name in SAP Logon System exactly as it is in the SAP Logon. Therefore, for each newly created session (some sessions are reused), you are routed to another server. For more information, see 3.4.1 Configuring Connections . In the example below, an SAP GUI session is started (the same SAP GUI session as if the corresponding entry in the SAP Logon is double-clicked, and the same load balancing settings are used).

The following figure shows the Systems dialog box and the SAP Logon in comparison:

SAP GUI Logon Description and SAP Logon

More Information

Transaction NWBC

~launch Page

Monitor the Message Server from the Browser

SAP Note 1040325 Information published on SAP site : HTTP load balancing: Message Server or Web Dispatcher

URL Generation in an AS-ABAP - Web Dispatcher Configuration

Configuration Table HTTPURLLOC