Message Server-Based Logon and Load Balancing (Redirection)


The SAP NetWeaver Application Server (AS) enables a message server based on redirect of HTTP/HTTPS requests.

The approach is the same as for logon load balancing with SAPGUI. The message server redirects the first request to the application server with the least workload. Each subsequent request is handled by the same server as the first request.


Each application server taking part in the load distribution tells the message server how many work processes it provides and whether it supports HTTP/HTTPS. When started, each HTTP client connects to the message server. The message server tells the client which server it has to connect to. HTTPS requests are only redirected to an application server accepting HTTPS.

Redirection has certain disadvantages that prevent it from being more extensively used in Internet scenarios:

?     The client has to access the message server and the application servers directly, which is to be avoided for security reasons.

?     The use of bookmarks is limited, as bookmarks always point to a particular application server.

?     It is necessary to provide an extra server certificate for each server because of the different URLs.

?     When a server fails there is no possibility of failover. A browser refresh is not sufficient, because the URL is no longer valid. The client has to connect to the message server again to initiate a new redirect.

However, the redirection approach does not need further precautions for stateful and HTTPS sessions because the session always remains on the same host.


To configure the message server to accept HTTP and HTTPS requests, you have to set the following parameters:

?     ms/http_port

?     ms/https_port

For more information on configuring message server-based HTTP load balancing, see the SAP NetWeaver AS documentation.

To make sure that the message server can be reached after a switchover, you have to use virtual names and addresses