RFR: 8297200: java/net/httpclient/SpecialHeadersTest.java failed once in AssertionError due to selector thread remaining alive [v4]

[Jaikiran Pai]

On Fri, 25 Nov 2022 12:15:47 GMT, Daniel Fuchs <dfuchs at openjdk.org> wrote:

>> The java/net/httpclient/SpecialHeadersTest.java test has been observed failing once, due to a selector thread still running after all operations had terminated. This change slightly alter the test logic to check the shared client only at the end of the test when all methods have been executed, and focussed the checks performed by a test method to the only clients that this method is using. This may or may not prevent the observed issue to ever reproducing, but should at least provide more information on where the selector manager thread is at the time it is observed running, should the test fail again:
>> the logic of the HttpClient should have woken up the selector when the last operation finished, which should have ensured a prompt termination of the thread.
>> In addition this change fixes a small race condition in the logic that attempts to decide if the selector is still alive: the selector should be considered alive until its run() method has been called and has exited (or Thread::start has thrown).
>
> Daniel Fuchs has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains five additional commits since the last revision:
> 
>  - Merge branch 'master' into SpecialHeadersTest-8297200
>  - Update test/jdk/java/net/httpclient/ReferenceTracker.java
>    
>    Co-authored-by: Andrey Turbanov <turbanoff at gmail.com>
>  - Fixed race condition in detecting if selector is still alive
>  - 8297200
>  - 8297200

test/jdk/java/net/httpclient/SpecialHeadersTest.java line 478:

> 476:                 if (!sameClient || client == null) {
> 477:                     client = newHttpClient("testAsync", sameClient);
> 478:                     tracker = TRACKER.getTracker(client);

Should this be outside this `if` block? Otherwise, in its current form, I think this `tracker` can be `null` and then later in this test where we do `TRACKER.check(tracker, ...)`, I believe it will lead to an NPE inside the `check` implementation.

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PR: https://git.openjdk.org/jdk/pull/11294