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

[Conor Cleary]

On Wed, 8 Jun 2022 18:29:10 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.

src/java.net.http/share/classes/jdk/internal/net/http/Stream.java line 306:

> 304:     @Override
> 305:     void expectContinueFailed(int rcode) {
> 306:         // TODO: add comment

Will add in a missing comment here!

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PR: https://git.openjdk.java.net/jdk/pull/9093