HttpClient async requests not completing for large batch sent out in a loop

Question

I think I\'ve managed to make a test that shows this problem repeatably, at least on my system. This question relates to HttpClient being used for a bad endpoint (no

Answer 1

I came across this question when googling for solutions to a similar problem from WCF. That series of exceptions is exactly the same pattern I see. Eventually through a ton of investigation I found a bug in HttpWebRequest that HttpClient uses. The HttpWebRequest gets in a bad state and only sends the HTTP headers. It then sits waiting for a response which will never be sent.

I've raised a ticket with Microsoft Connect which can be found here: https://connect.microsoft.com/VisualStudio/feedback/details/1805955/async-post-httpwebrequest-hangs-when-a-socketexception-occurs-during-setsocketoption

The specifics are in the ticket but it requires an async POST call from the HttpWebRequest to a non-localhost machine. I've reproduced it on Windows 7 in .Net 4.5 and 4.6. The failed SetSocketOption call, which raises the SocketException, only fails on Windows 7 in testing.

For us the UseNagleAlgorithm setting causes the SetSocketOption call, but we can't avoid it as WCF turns off UseNagleAlgorithm and you can't stop it. In WCF it appears as a timed out call. Obviously this isn't great as we're spending 60s waiting for nothing.