RFR: 8350279: HttpClient: Add a new HttpResponse method to identify connections [v12]

[Daniel Fuchs]

On Tue, 8 Apr 2025 19:27:17 GMT, Volkan Yazici <vyazici at openjdk.org> wrote:

>> Adds `HttpResponse::connectionLabel` method that provides an identifier for the connection.
>> 
>> **Implementation note:** The feature is facilitated by `HttpConnection::label`, which should not be confused with `HttpConnection::id`. This distinction is explained in the JavaDoc of both properties.
>
> Volkan Yazici has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Add `@implNote` to state that the built-in is always non-empty

Changes requested by dfuchs (Reviewer).

test/jdk/java/net/httpclient/HttpResponseConnectionLabelTest.java line 188:

> 186:         private static HttpTestServer createServer(Version version, SSLContext sslContext) {
> 187:             try {
> 188:                 return HttpTestServer.create(version, sslContext, ForkJoinPool.commonPool());

OK - we definitely MUST NOT use the common FJP here. 

1. our HTTP/2 servers start their dispatching thread, which blocks on accept(), in the executor. 
2. the tests will block (CountDownLatch) in the exchange, which is a thread in the executor.
3. the test creates at least two HTTP/2 servers (maybe more) upfront.

If you run this test on a machine that has a low number of processors - say 4 - then the FJP will maybe have 3 threads at most. You can see where that goes...

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

PR Review: https://git.openjdk.org/jdk/pull/24154#pullrequestreview-2761151791
PR Review Comment: https://git.openjdk.org/jdk/pull/24154#discussion_r2040042478