RFR: 8304963: HttpServer closes connection after processing HEAD after JDK-7026262

[Daniel Fuchs]

On Mon, 27 Mar 2023 18:37:58 GMT, Daniel Jeliński <djelinski at openjdk.org> wrote:

> This PR fixes a regression introduced in [JDK-7026262](https://bugs.openjdk.org/browse/JDK-7026262); we started closing the exchange instead of the output stream, and exchange closes the connection when wrapped stream is not set. As an unintended side effect, the server started closing connections after handling a HEAD request.
> 
> The proposed change is to set the wrapped stream to a zero-length FixedLengthOutputStream before closing the exchange. This allows the connection to be reused.
> 
> The attached test verifies if 2 consecutive HEAD requests use the same connection. It succeeds with the proposed change, fails without it. All other tier1-3 tests continue to pass.

Good finding. We missed the case where the response output stream didn't get wrapped for the HEAD request which caused the socket stream to get closed.
The HTTP server in the new test will only triggers if the URI path is /firstCall or /secondCall so it should hopefully be resilient to random connections. 
Please verify the new (and old) tests are stable before integrating.

-------------

Marked as reviewed by dfuchs (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/13193#pullrequestreview-1359703061