dotnet performance: Asynchronous WebRequests? -- dotnet performance

RE: Asynchronous WebRequests?

john conwell
6/24/2005 8:14:07 AM

You should definitly not do the sleep. What if the requests take too long,
and 30 isnt long enough?

Generally speaking, when doing multiple async web service requests, take the
IAsyncResult.AsyncWaitHandle from each web service call and slap then into an
array. then call WaitHandle.WaitAll() passing in the array of
AsyncWaitHandles. This will block the current thread until all the web
service calls have completed.

Now, a few things to think about. Is your web site usually under a heavy
load (high number of users)? If so, then kicking off 3 async web services per
request to this page might be a bad idea, because you'll be stealing 3
threads from the thread pool used to service other requests. this doesent
scale very well at all.

If you really want to do the async web service calls, another technique is
to create a IHttpHandler to intercept your request, kick off the three web
service calls and store the handle array in HttpContext.Items hashtable. The
forward the request onto the correct page and in the page do the
WaitHandle.WaitAll(). this gives the request a few extra moments to process
the web service calls before they have to sync back up again.

hot this helps

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RE: Asynchronous WebRequests?

john conwell
6/24/2005 8:19:04 AM

Here is an article on MSDN that talkes about the httphandler kicking off the
web service like i mentioned in my previous post

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnservice/html/service07222003.asp

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RE: Asynchronous WebRequests?

Dave
6/27/2005 9:10:02 AM

John, thanks for the responses. I'd like to get this to work and then do some
load testing. I'm having trouble using the WaitAll(). I guess I thought it
would wait for all handles to respond but the "Done" if else block gets fired
before the responses return.

I'm concatenating the responses in in a textarea to display all the results.
Maybe my understanding of this is off...

HttpWebRequest wreq;
IAsyncResult r0;
IAsyncResult r1;
IAsyncResult r2;

WaitHandle[] handleArray;
handleArray = new WaitHandle[3];

wreq = (HttpWebRequest) WebRequest.Create("http://somefeed0");
r0 = (IAsyncResult) wreq.BeginGetResponse(new
AsyncCallback(this.RespCallback), wreq);
handleArray[0] = r0.AsyncWaitHandle;

wreq = (HttpWebRequest) WebRequest.Create("http://somefeed1");;
r1 = (IAsyncResult) wreq.BeginGetResponse(new
AsyncCallback(this.RespCallback), wreq);
handleArray[1] = r1.AsyncWaitHandle;

wreq = (HttpWebRequest) WebRequest.Create("http://somefeed2");
r2 = (IAsyncResult) wreq.BeginGetResponse(new
AsyncCallback(this.RespCallback), wreq);
handleArray[2] = r2.AsyncWaitHandle;

if(WaitHandle.WaitAll(handleArray, 30000, false))
{
Response.Write("Done");
}
else
{
// The wait operation times out.
Response.Write("Timeout");
}

}

private void RespCallback(IAsyncResult ar)
{
HttpWebRequest req = (HttpWebRequest) ar.AsyncState;
HttpWebResponse resp = (HttpWebResponse) req.EndGetResponse(ar);

//Wrap the response stream with a text-based reader
StreamReader sr = new StreamReader(resp.GetResponseStream(),
System.Text.Encoding.UTF8);

string strStream = sr.ReadToEnd();

// Close the response to free resources.
sr.Close();
resp.Close();

txtHTML.InnerHtml += strStream;
}

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Re: Asynchronous WebRequests?

Anders Matthiessen
6/29/2005 9:51:57 AM

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I wonder how you didnt find this one instead:
ajax.net : http://weblogs.asp.net/mschwarz/

It works like a charm. Samples and code is available at
http://ajax.schwarz-interactive.de/csharpsample/default.aspx

Its even opensource ! :-)

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