RFR: 8308310: HttpClient: Avoid logging or locking from within synchronized blocks [v8]

[Jaikiran Pai]

On Tue, 23 May 2023 15:11:10 GMT, Daniel Fuchs <dfuchs at openjdk.org> wrote:

>> Please find here a change that revisits usage of monitors in the HttpClient.
>> 
>> With Virtual Threads now part of the platform it should be possible to pass a newVirtualThreadPerTaskExecutor to the HttpClient. Logging, when enabled, and when called from a synchronized block, can cause the carrier thread to get pinned in case of contention when printing through the underlying PrintStream.
>> 
>> This change aims at avoiding situations where the carrier threads might get pinned.
>
> Daniel Fuchs has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 11 commits:
> 
>  - Merge branch 'master' into HttpClient-Logging-8308310
>  - Merge branch 'master' into HttpClient-Logging-8308310
>  - Fix whitespace
>  - make stateLock final
>  - Add debug traces to ExpectContinueTest.java
>  - failedRef should be final
>  - Align parameters
>  - Update src/java.net.http/share/classes/jdk/internal/net/http/Http1Response.java
>    
>    Co-authored-by: Andrey Turbanov <turbanoff at gmail.com>
>  - Update src/java.net.http/share/classes/jdk/internal/net/http/ConnectionPool.java
>    
>    Co-authored-by: Andrey Turbanov <turbanoff at gmail.com>
>  - Update test/jdk/java/net/httpclient/AuthFilterCacheTest.java
>    
>    Co-authored-by: Andrey Turbanov <turbanoff at gmail.com>
>  - ... and 1 more: https://git.openjdk.org/jdk/compare/c0c4d771...c5d2f1f2

src/java.net.http/share/classes/jdk/internal/net/http/MultiExchange.java line 218:

> 216:         synchronized (this) {
> 217:             previousExchange = this.exchange;
> 218:             this.exchange = exchange;

There's a behavioural change here as compared to before this change. Previously, we used to first call `released()` on the old exchange and `cancel()` the new exchange, before setting the `this.exchange` to the new exchange. Now, with this change, we first switch the `this.exchange` to the new exchange and then call `released()` and `cancel()`. Do you think that could have any (odd) issues?

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PR Review Comment: https://git.openjdk.org/jdk/pull/14038#discussion_r1203930954