How to use CancellationToken with HttpClient

[MhdTlb]

I'm trying to setup a timeout for each separate HttpClient.Send call in .net8.0.

So I used CancellationTokenSource but It seems that it starts the timer as soon as I create it instead of starting the timer when calling HttpClient Send method.
Here is my unit tests result:

[TestMethod]
[DataRow(1)]
[DataRow(10)]
[DataRow(100)]
[DataRow(1000)]
[DataRow(10000)]
[DataRow(100000)]
[DataRow(1000000)]
public void HttpClient_Send_CancellationTokenSource(int timeout)
{
    var httpClient = new HttpClient();
    var cts = new CancellationTokenSource(TimeSpan.FromMilliseconds(timeout));

    var request = new HttpRequestMessage(HttpMethod.Get, "https://google.com");
    Thread.Sleep(2 * timeout);
    var response = httpClient.Send(request, cancellationToken: cts.Token);
}

So all unit tests failed with this exception: System.Threading.Tasks.TaskCanceledException: The operation was canceled. ---> System.OperationCanceledException: The operation was canceled.

[wfurt]

since you sleep before the send, the token will be expired before you get to the send. What are you trying to do here @MhdTlb ?

[MhdTlb]

Hmmm I was expecting that the CancellationTokenSource timer starts exactly when calling HttpClient.Send. That way the timeout would be really measuring the Http request time and not the .net time to setup and invoke HttpClient.

[wfurt]

HttpClient is consumer of the token. It does not interact with any any active way and it simply stops processing when token is cancelled e.g. CancellationToken.IsCancellationRequested

[colejohnson66]

In most cases, the overhead of HttpClient itself doesn’t matter; the user cares about overall time spent retrieving a resource, not just the actual HTTP time. So a cancellation token is the perfect mechanism to stop a request.

[ManickaP]

If your goal is just timeout and not cancellation based on other event, you can use HttpClient.Timeout. Note that you can set this only before you send your first request on the client and you cannot change it afterwards. So for different timeouts per request, it's still better to use the CancellationToken.