How can I tell when HttpClient has timed out

Question

As far as I can tell  there s no way to know that it s specifically a timeout that has occurred  Am I not looking in the right place  or am I missing something bigger  string baseAddress    quot http   localhost 8080  quot   var client   new HttpClient           BaseAddress   new Uri baseAddress        Timeout   TimeSpan FromMilliseconds 1      try       var s   client GetAsync  quot  quot   Result    catch Exception e        Console WriteLine e Message       Console WriteLine e InnerException Message      This returns   One or more errors occurred  A task was canceled

User · Answer

From http   msdn microsoft com en-us library system net http httpclient timeout aspx     A Domain Name System  DNS  query may take up to 15 seconds to return or time out  If your request contains a host name that requires resolution and you set Timeout to a value less than 15 seconds  it may take 15 seconds or more before a WebException is thrown to indicate a timeout on your request    You then get access to the Status property  see WebExceptionStatus

User · Answer

httpClient   new HttpClient handler   Timeout   TimeSpan FromSeconds 5      is what I usually do  seems to work out pretty good for me  its especially good when using proxies

User · Answer

Basically  you need to catch the OperationCanceledException and check the state of the cancellation token that was passed to SendAsync  or GetAsync  or whatever HttpClient method you re using     if it was canceled  IsCancellationRequested is true   it means the request really was canceled if not  it means the request timed out   Of course  this isn t very convenient    it would be better to receive a TimeoutException in case of timeout  I propose a solution here based on a custom HTTP message handler  Better timeout handling with HttpClient

User · Answer

As of  NET 5  the implementation has changed  HttpClient still throws a TaskCanceledException  but now wraps a TimeoutException as InnerException  So you can easily check whether a request was canceled or timed out  code sample copied from linked blog post   try       using var response   await  client GetAsync  quot http   localhost 5001 sleepFor seconds 100 quot         Filter by InnerException  catch  TaskCanceledException ex  when  ex InnerException is TimeoutException           Handle timeout      Console WriteLine  quot Timed out   quot   ex Message     catch  TaskCanceledException ex           Handle cancellation      Console WriteLine  quot Canceled   quot    ex Message

User · Answer

I found that the best way to determine if the service call has timed out is to use a cancellation token and not the HttpClient s timeout property   var cts   new CancellationTokenSource    cts CancelAfter timeout     And then handle the CancellationException during the service call     catch TaskCanceledException        if  cts Token IsCancellationRequested                   Timed Out           else                  Cancelled for some other reason           Of course if the timeout occurs on the service side of things  that should be able to handled by a WebException

User · Answer

I am reproducing the same issue and it s really annoying  I ve found these useful   HttpClient - dealing with aggregate exceptions  Bug in HttpClient GetAsync should throw WebException  not TaskCanceledException  Some code in case the links go nowhere   var c   new HttpClient    c Timeout   TimeSpan FromMilliseconds 10   var cts   new CancellationTokenSource    try       var x   await c GetAsync  http   linqpad net   cts Token       catch WebException ex           handle web exception   catch TaskCanceledException ex        if ex CancellationToken    cts Token                   a real cancellation  triggered by the caller           else                  a web request timeout  possibly other things

User · Answer

You need to await the GetAsync method   It will then throw a TaskCanceledException if it has timed out  Additionally  GetStringAsync and GetStreamAsync internally handle timeout  so they will NEVER throw   string baseAddress    http   localhost 8080    var client   new HttpClient           BaseAddress   new Uri baseAddress        Timeout   TimeSpan FromMilliseconds 1      try       var s   await client GetAsync      catch Exception e        Console WriteLine e Message       Console WriteLine e InnerException Message

[c#] How can I tell when HttpClient has timed out?

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