Strategies for Web Service to Unmanaged DLL

Discussion in 'ASP .Net Web Services' started by David Palau, Oct 20, 2006.

  1. David Palau

    David Palau Guest

    We have a C#, .NET 1.1 web service that will be interacting with a
    third-party, unmanaged DLL.

    The idea is that this web service will be called with certain
    parameters from within our intranet, passing along these parameters to
    a function ( DoSomething() ) in this third-party DLL which will return
    back to us a double number which we will return from our web service.
    This web service method will be hit ~2500 times per day.

    However, in order to interact with this third-party DLL, we need to
    start it up so to speak. Basically this means that we need to notify
    this third-party DLL that we will be interacting with it through an
    initialization function ( Open() ). This Open() call will return to us
    a unique integer number to use in any subsequent calls to
    DoSomething().

    When we are finished calling DoSomething(), we need to notify it that
    we are done with our requests and it can 'release' this unique
    license number from being used (Close() ). If we attempt to call
    Open() again before we call Close() we won't be given a new license
    number to use.

    Due to stability issues and the amount of resources it takes to call
    the third-party DLL Open() and Close(), it was recommended to us by the
    vendor of this DLL that we only call Open() once and then do as many
    DoSomething() calls as we need to. Only doing a Close() call when we
    need to shut everything down - which I guess only happens when we
    have to reboot the web server or reset IIS completely or something.

    Initially we were storing our 'license' number as a static variable
    in a static class in a separate assembly referenced by our web service
    and calling Open() on the DLL during the Application_Start event in
    Global.asax and calling Close() during the Application_End event. Our
    actual DLLImport references were also in this static class.

    However, due to when IIS recycles the worker process, which obviously
    gets rid of the static variable, and I guess 'unloads' the third-party
    DLL, the Application_End event wasn't being called in the normal
    process of the recycle (at least it wasn't before a new
    Application_Start would fire off). This would result in a failure when
    we tried Open() or DoSomething() again.

    So we need to come up with a new way to make sure we handle the Open()
    and Close() calls intelligently. Do these ideas make any sense:

    1. Totally disable the IIS recycling feature in the application pool we
    are using in IIS so theoretically the process will never recycle,
    always leaving that static variable and reference to the DLL around.

    2. Putting the interaction of the third-party DLL in some sort of
    windows service for the web service to interact with. We don't allow
    anonymous access to this web service and use Basic authentication using
    SSL so we should be able to impersonate the caller or set up some
    service account that we can grant access to reference this windows
    service. This way this windows service can be around at web server
    startup and it can manage the Open()/Close()/DoSomething() calls. How
    do you interact with a .Net managed windows service from a web service?

    3. Something else???


    Sorry for the long post, but if anyone has any leads, it would be
    greatly appreciated.

    Thanks,

    -David
    David Palau, Oct 20, 2006
    #1
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