Timeout behaviour in HttpWebRequest.GetResponse() vs GetResponseAsync()

Question

When I try the following code:

var request = (HttpWebRequest)HttpWebRequest.Create(url);
request.Timeout = 3; // a small value

var response = request.GetResponse();
Console.WriteLine(response.ContentLength);

for a URL that I know it is going to take more than 3 millisecond to load (I put a Thread.Sleep(110000) in Application_BeginRequest) it works fine and throws a WebException as expected.

Problem is when I switch to async method:

var response = request.GetResponseAsync().Result;

or

var response = await request.GetResponseAsync();

This async version completely ignores any Timeout value, including ReadWriteTimeout and ServicePoint.MaxIdleTime

I couldn't find anything about Timeout in MSDN's GetResponseAsync() now I'm wondering if it is a bug in GetResponseAsync() or something is wrong in the way I use async here?

see answer in http://stackoverflow.com/questions/4238345/asynchronously-wait-for-taskt-to-complete-with-timeout — artm, Oct 06 '14 at 10:31
Does it mean they intentionally ignore Timeout in all async APIs? I find that hard to believe. For example in this specific case this leaves the API user with no way to set different timeout values for different stages like ReadWriteTimeout/ContinueTimeout — el_shayan, Oct 06 '14 at 10:37

score 24 · Accepted Answer · answered Oct 06 '14 at 11:03

24

Timeout does not apply to asynchronous HttpWebRequest requests. To quote the docs:

The Timeout property has no effect on asynchronous requests

I recommend you use HttpClient instead, which was designed with asynchronous requests in mind.

answered Oct 06 '14 at 11:03

Stephen Cleary

437,863
77
675
810

4

"The Timeout property has no effect on asynchronous requests **made with the BeginGetResponse or BeginGetRequestStream method.**": docs are not about GetResponseAsync, but answer is right anyway, because GetResponseAsync uses BeginGetResponse inside. – VorobeY1326 Nov 28 '14 at 12:52

score 0 · Answer 2 · answered Sep 01 '18 at 14:31

0

Follow a solution to solve the problem.

await Task.Run(() => { 
  var varHttpResponse = varWebRequest.GetResponse(); 
});

answered Sep 01 '18 at 14:31

Lucas Lima

9
2

This works, but you may now have a runaway open connection, and they can accumulate over time. – Cristian Diaconescu Nov 01 '19 at 16:15
Fake async - this blocks. – tmaurst Feb 19 '21 at 06:35

Timeout behaviour in HttpWebRequest.GetResponse() vs GetResponseAsync()

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