Skip to Content

Parallel WebDispatchers - WebDynpro termination with "A request for server & was sent to server &."

Hi,

We are moving our SAP systems from on-premise into Azure, and as part of the move we are implementing 2 (parallel) Web Dispatchers in front of our ECC system to handle HTTP (WebDynpro) traffic. The 2 parallel Web Dispatchers are implemented for HA, and are load balanced by an Azure Internal Load Balancer (ILB) using simple round robin. WebDispatcher version is 7.45.

Generally this seems to be working fine, however we do get intermittent errors "A request for server & was sent to server &.", terminating the WebDynpro function.

I have seen 2-3 previous posts regarding this error, however couldn't find any exact "solution" or cause. I can't see any related information in the WebDispatcher log, and I'm not really sure where else to start investigating.

Has anyone else encountered and resolved this issue? Would be especially interested if anyone has implemented a similar setup in Azure.

Thanks!

Todd

Add comment
10|10000 characters needed characters exceeded

  • Get RSS Feed

2 Answers

  • Jan 10 at 02:29 PM

    Hello Todd Scholes,

    Can you please look at SAP help link below?

    High Availability of the SAP Web Dispatcher

    https://help.sap.com/saphelp_nw74/helpdata/en/48/9a9a6b48c673e8e10000000a42189b/content.htm?loaded_from_frameset=true

    First line under section : High Availability with Parallel Web Dispatchers

    You can provide high availability with parallel SAP Web Dispatchers too. Both Web Dispatchers have the same configuration and forward their requests to the target system. Since stickiness is achieved by using a cookie, a stateful request will get to the correct application server in any case.

    In your case this is what not happening what I have highlighted.

    Thank you

    Yogesh

    Add comment
    10|10000 characters needed characters exceeded

  • Jan 10 at 11:57 PM

    Hello Todd,

    The feature highlighted by Yogesh (in bold) is somewhat new.

    What is the patch level of the Web Dispatcher 7.45 being used?

    You might consider upgrading the Web Dispatcher to the latest patch level of the 7.49 release, as this is the recommended version (read the SAP Note 908097 - S-user required).

    Regards,

    Isaías

    Add comment
    10|10000 characters needed characters exceeded

    • Hello Todd,

      You are welcome!

      If the issue persisted even with one Web Dispatcher only, then I would agree that the issue would not be occurring because of the parallel Web Dispatchers.

      You can verify whether the Azure load balancer is tampering with HTTP headers / cookies.

      It might be removing headers/cookies that SAP needs (like "MYSAPSSO2").

      Regards,

      Isaías