RFR: 8296410: HttpClient throws java.io.IOException: no statuscode in response for HTTP2

[Conor Cleary]

On Mon, 23 Jan 2023 15:00:07 GMT, Conor Cleary <ccleary at openjdk.org> wrote:

>> ### **Description**
>> With HTTP/2, a possible flow of an exchange could be that a Server responds to a simple request by sending response headers within a HEADERS frame, the requested resources and trailing headers with another HEADERS frame including the END_HEADERS and END_STREAM flags (if they were not previously given in the Response Headers). Usually an HTTP/2 client should opt-in to make use of trailing headers though this behaviour is not supoorted by default with the HttpClient. 
>> 
>> It is still possible in any case that a trailing HEADERS frame can be sent, even if the frame just carries flags and no headers specified in the header block. This edge case was causing an IOException to be thrown and the client to shut down unexpectedly.
>> 
>> ### **Summary of Changes & Justification**
>> In Stream, a means to track the state of whether or not a final status code for an exchange has been received was added to prevent the exception occuring due to a HEADERS frame with no status code arriving after response headers were received. In the case of a partial response (status codes in the 1XX range), the flag for receiving a final response code is not set until a response outside of the 1XX range is received.
>> 
>> Lastly, if trailing headers are received, they are logged and dumped. The response headers consumer is then reset.
>> 
>> ---------
>> ### Progress
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>
> Semi-related, a previous fix concerning Push Promises: https://github.com/openjdk/jdk/pull/8518

> ⚠️ @c-cleary This pull request contains merges that bring in commits not present in the target repository. Since this is not a "merge style" pull request, these changes will be squashed when this pull request in integrated. If this is your intention, then please ignore this message. If you want to preserve the commit structure, you must change the title of this pull request to `Merge <project>:<branch>` where `<project>` is the name of another project in the [OpenJDK organization](https://github.com/openjdk) (for example `Merge jdk:master`).

This is due to local squashing of commits, can be ignored. I have verified the correctness of the changeset

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PR: https://git.openjdk.org/jdk/pull/12028