High Availability with Parallel Web Dispatchers.

Soft Shutdown and Startup of Parallel Web Dispatchers;CASE STUDYThe portal system EP includes a Web Dispatcher (WD1) that is situated in front of the portal servers, facilitating load balancing for incoming requests. Within the portal, an iView allows access to an SAP application hosted in a back-end system, which comprises several instances and utilizes another Web Dispatcher (WD2) for load balancing.The communication among the various components operates in the following manner: the client, typically a browser, initiates a request that is routed through the Web Dispatcher to the portal system. When a user activates a request within an iView, it necessitates processing by the back-end system, leading to the generation of a URL in the Portal, which is then sent to the client. The client utilizes this URL for subsequent requests, which are directed through the Web Dispatcher to an instance in the back-end system, where the response is formulated and returned to the client. For this process to function effectively, the Web Dispatcher must maintain an internal status in relation to the back-end system (WD2), and high availability can only be achieved with two parallel Web Dispatchers if an external load balancer is employed to ensure that requests from the same user consistently reach the same Web Dispatcher. Additionally, high availability at the process level is supported, or an HA setup can be implemented using external software. Conversely, Web Dispatcher WD1 can be configured for high availability without limitations by utilizing a parallel activated Web Dispatcher. This entire process is illustrated in the accompanying graphic