"lowlyscrub" wrote:

> I have an ASP.NET application that makes 12 different web service calls
> from a single method call. Each of the web services themselves don't
> do much more than run a small query (I've run the queries elsewhere and
> they complete virtually instantaneously) on some database and return a
> dataset. As it so happens, the 12 calls are split up between 4
> different web services on the same server, and the web services
> themselves are ASP.NET apps built in C#. Anyway, I know that each
> individual call usually returns in less than 10 seconds (first call).
> I encounter problems only when I try to call them one after another in
> my application.
>
> The code looks something like this:
> // create proxy objects
> WSa.WebService a = new WSa.WebService();
> ....
> WSd.WebService d = new WSd.WebService();
>
> // Fill up datasets with web service calls
> DataSet ds1 = a.Call1();
> DataSet ds2 = a.Call2();
> ....
> DataSet ds7 = c.Call(1);
> ....
> DataSet ds12 = d.Call3();
>
> // Do other processing with data
> ....
>
> The most time-consuming call returns a chunk of data on the order of
> 2.5MB in size, but most of the SOAP messages returned are less than
> 150k.
>
> When I put some timing code in there, I found that it could take from
> ~124 seconds to ~1290 seconds for the same 12 calls to complete (they
> returned the same data every time in my tests). The server hosting the
> web services did not ever appear to be under heavy load (I did a remote
> desktop to it and put up task manager to watch).
>
> I have tried running them asynchronously, and the total response time
> for all of the calls to return -- I need all the data returned before I
> can proceed, so I have to wait for all End calls to finish anyway --
> still varies greatly. The one thing I learned from the asynchronous
> calls is that certain calls among the 12 are far more likely to take
> much longer than others. In fact, they take much longer than they
> normally would if I just called each of them separately rather than all
> 12 in sequence. I even wrote a test application with buttons to do
> just that, and the total time it takes for me to click all 12 buttons
> and get a response is always less than 2 minutes.
>
> Why is there such a variation in response time? What can I do to get
> these web service calls to run faster?
>