RFR: 8347597: HttpClient: improve exception reporting when closing connection

[Jaikiran Pai]

On Mon, 13 Jan 2025 16:07:45 GMT, Daniel Fuchs <dfuchs at openjdk.org> wrote:

> There are a few places in the HttpClient code base where we close the connection when some error/exception happens. This can some time trigger a race condition where closing the connection in turns causes a "connection closed locally" exception to get reported instead of the original exception. This typically happens if another thread is attempting to read from / write to the connection concurrently when the original exception that caused the connection to get closed occurred. 
> 
> The fix makes sure that we store the first exception in the underlying connection before closing it, and that this is the exception that gets subsequently reported.
> 
> Some minor drive by test fixes. No new regression test.

test/jdk/java/net/httpclient/http2/ExpectContinueResetTest.java line 104:

> 102:             testThrowable = e.getCause();
> 103:         }
> 104:         assertNotNull(exception, "Request should have completed exceptionally but exception is null");

Unlike the `assertNotNull` on the next line, I think it might be better to replace this new `assertNotNull` with a `fail(...)` inside the try block immediately after the `performRequest()` call.

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PR Review Comment: https://git.openjdk.org/jdk/pull/23080#discussion_r1914555193