HTTP Load Distribution 

Use

For your ICF services (BSPs, web dynpros, web services, ITS applications and so on), you can set HTTP load distribution. This forwards the service calls to the application server that has the most capacity at the time of the call.

Integration

Load distribution is performed either over a message server or over the SAP web dispatcher.

Prerequisites

The following ICF services have been activated:

¡        /sap/public/icf_info

¡        /sap/public/icf_info/icr_groups

¡        /sap/public/icf_info/icr_urlprefix

Using these services, the message server or the web dispatcher receives the load distribution information that is defined in the ICF service.

  

You can activate the relevant services using ABAP report RSICF_SERVICE_ACTIVATION and with input value MESSAGESERVER-LOADBALANCING or WEBDISPATCHER-LOADBALANCING for input parameter TECHNME. In older Releases, these services can only be activated using transaction SICF.  

Features

The Internet Communication Framework (ICF) supports two types of load distribution:

·        Load distribution over the message server: Here, while the connection is established, the host name of the message server and its HTTP/HTTPS port are addressed. After the HTTP/HTTPS connection to the message server has been established, the message server chooses the participating server group in accordance with the request path. The request is forwarded by an HTTP redirect to the target computers in the server group that has the most capacity.

·        Load distribution over the web dispatcher: Here, while the connection is established, the host name of the web dispatcher and its HTTP/HTTPS port must be addressed.

Activities

Maintaining logon groups in the ICF service

For each service/service node, define a logon group (see Defining Service Data).

Determining Host/Port Information

·        You can determine the message server's host name and HTTP/HTTPS ports using transaction SMMS

¡        Display the host name of the message server: In the menu, choose Goto → Parameters  →   Display →  Server host (fqn).

Note: If the host name is used as an HTTP URL and does not contain the domain, the domain is always added to it.

¡        Display HTTP/HTTPS port: In the menu, choose Goto → Parameters  →   Display  →   ms/http_port oder ms/https_port.

If these entries are not defined, you must define these profile parameters for the message server.

Define the profile parameters ms/server_port_ for HTTP/HTTPS ports of the virtual host (such as ms/server_port_0 = PROT=HTTP,PORT=8080,VHOSTIDX=0 and ms/server_port_1 = PROT=HTTPS ,PORT=8443).

                    

The profile parameters listed above are dynamic parameters and can also be maintained directly in transaction SMMS for test purposes, via Goto  →Parameters  → Change.

Logon groups check

·        Using the HTTP request http://<Messageserhost>:<Messageserverport>/msgserver, you can determine a list of the message server functions. The /msgserver/lglist path provides the list of GUI logon groups.

If no load distribution takes place despite the HTTP/HTTPS ports being activated for the message server and the ICF services being activated for load distribution, you can check whether the message server has received the relevant information for load distribution from the Internet Communication Framework (ICF).

·        Call transaction SMMS and choose Goto → Expert Functions → HTTP → URL Logon Groups. A list is displayed of the ICF services for which a GUI logon group for load distribution has been entered. If this list is empty, you can provide the information by choosing Goto → Expert Functions → HTTP → Load URL Groups.

·        Call transaction SMMS and choose Goto → Expert Functions → HTTP → URL Prefixes. A list is displayed of the ICF services that are used as a URL prefixes for message servers. If this list is empty, you can get the information by choosing Goto → Expert Functions → HTTP → Load URL Prefixes.

Additional Information

For documentation on HTTP load distribution over message servers, see:

·        HTTP Load Distribution over the Message Server

For detailed information about the Web Dispatcher, see:

·        SAP Web Dispatcher

For information on configuring the message server or the web dispatcher for load distribution, see the following documentation:

·        Configuring the SAP Web Dispatcher / Message Server for Virtual Hosts

For details about message server administration, see:

·        Monitoring and Administration of the SAP Message Server