RFR: 8343855: HTTP/2 ConnectionWindowUpdateSender may miss some unprocessed DataFrames from closed streams [v3]

[Jaikiran Pai]

On Tue, 12 Nov 2024 19:43:45 GMT, Daniel Fuchs <dfuchs at openjdk.org> wrote:

>> [JDK-8342075](https://bugs.openjdk.org/browse/JDK-8342075) has introduced more flow controls checks, but also introduced a race condition where DataFrames for closed streams may fail to be discounted from the connection window.
>> 
>> The consequence is that WINDOW_UPDATE frames for the connection window may not be sent when they should, preventing the server from making progress and stalling the connection.
>> 
>> This can be shown by modifying the StreamFlowControlTest to send less but bigger frames (e.g. chunks of 1600 bytes instead of chunks of 12 bytes). With such a modification the test can be seen failing intermittently, when sameClient=true.
>> 
>> The race happens when frames that have been added to Stream::inputQ fail to be drained after the stream is closed (or continue to be added to the inputQ after the stream is closed).
>> 
>> The fix ensures that Stream::drainInputQueue() is called when the stream is closed, and that no further data farme will be added to the inputQ after the stream is marked closed.
>> 
>> The modified StreamFlowControlTest could be observed failing relatively frequently on linux-aarch64 without the fix.
>> With the fix the test no longer fails.
>
> Daniel Fuchs has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Update test/jdk/java/net/httpclient/http2/StreamFlowControlTest.java
>   
>   Co-authored-by: Andrey Turbanov <turbanoff at gmail.com>

test/jdk/java/net/httpclient/lib/jdk/httpclient/test/lib/common/HttpServerAdapters.java line 434:

> 432:      * The response is always returned with fixed length.
> 433:      */
> 434:     public static class HttpHeadHandler implements HttpTestHandler {

The class name is slightly misleading since this also handles `GET`. Perhaps `HeadOrGetHandler` would be appropriate?

test/jdk/java/net/httpclient/lib/jdk/httpclient/test/lib/common/HttpServerAdapters.java line 467:

> 465:                 }
> 466:             }
> 467:             t.getResponseBody().close();

It's a `HttpTestExchange`, so we don't have clear defined semantics for what happens when `HttpTestExchange.getResponseBody()` is invoked after the response body is already `close()`d previously. I think it might be better to move this `t.getResponseBody().close()` into the individual `case` blocks to avoid calling `t.getResponseBody()` after the `case GET` already closes the response body in its try-with-resources.

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PR Review Comment: https://git.openjdk.org/jdk/pull/21991#discussion_r1839947396
PR Review Comment: https://git.openjdk.org/jdk/pull/21991#discussion_r1839945465