RFR: 8286171: HttpClient/2 : Expect:100-Continue blocks indefinitely when response is not 100 [v4]

[Daniel Fuchs]

On Thu, 9 Jun 2022 13:06:34 GMT, Conor Cleary <ccleary at openjdk.org> wrote:

>> **Issue**
>> It was observed that when the httpclient sends a POST request with the `Expect: 100 Continue` header set and the server replies with a response code `417 Expectation Failed` that the httpclient hangs indefinitely when the version of Http used is HTTP/2. However, it was also seen that the issue persisted with HTTP/1_1 with the same usage.
>> 
>> This was caused by an implementation in ExchangeImpl that resulted in two calls to readBodyAsync() in this case, where the second call causes the indefinite hanging (as if there was a respomse body, it has already been read).
>> 
>> **Solution**
>> When ExchangeImpl::expectContinue() detects that a response code 417 is received, two things occur. Firstly, a flag is set which ensures that the connection is closed locally in this case. Secondly, the response is returned to the client as a failed future, A unit test was added to ensure that this usage of the httpclient does not cause hanging.
>
> Conor Cleary has updated the pull request incrementally with one additional commit since the last revision:
> 
>   8286171: Updated comment

LGTM Conor. Please integrate when you are ready and drop me a note: I will sponsor.

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Marked as reviewed by dfuchs (Reviewer).

PR: https://git.openjdk.org/jdk/pull/9093