RFR: 8267140: Support closing the HttpClient by making it auto-closable [v4]

[Jaikiran Pai]

On Mon, 20 Mar 2023 10:57:05 GMT, Daniel Fuchs <dfuchs at openjdk.org> wrote:

>> Please find here an RFE that makes the `java.net.HttpClient` auto-closeable.
>> 
>> The API has been modeled on `ExecutorService`.
>> 
>> HttpClient::close() is a graceful shutdown and will wait until all operations are terminated before returning.
>> If a request is in progress, and the caller doesn't pull the corresponding data (for instance, the request was sent with a BodyHandler.ofInputStream(), but the caller stopped reading the input stream) then close() may never return.
>> 
>> Therefore, additional methods similar to those present in `ExecutorService` are also proposed. In summary:
>> 
>> - `shutdown()`: initiate a graceful shutdown, but doesn't wait for termination. 
>> - `shutdownNow()`:  initiate an immediate shutdown, attempting to cancel all operations in progress. Doesn't wait for termination.
>> - `awaitTermination(Duration)`: await for termination within the given delay
>> - `isTerminated()` tells whether the client is terminated
>> 
>> New tests have been added to test the proposed behaviors.
>> 
>> HttpClient tests (new and old) are still stable.
>
> 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 10 additional commits since the last revision:
> 
>  - Merge branch 'master' into HttpClient-close-8267140
>  - Update test/jdk/java/net/httpclient/HttpClientShutdown.java
>    
>    Co-authored-by: Andrey Turbanov <turbanoff at gmail.com>
>  - Update test/jdk/java/net/httpclient/ShutdownNow.java
>    
>    Co-authored-by: Andrey Turbanov <turbanoff at gmail.com>
>  - Update test/jdk/java/net/httpclient/HttpClientShutdown.java
>    
>    Co-authored-by: Andrey Turbanov <turbanoff at gmail.com>
>  - Update test/jdk/java/net/httpclient/AsyncShutdownNow.java
>    
>    Co-authored-by: Andrey Turbanov <turbanoff at gmail.com>
>  - Review feedback
>  - typo
>  - Merge branch 'master' into HttpClient-close-8267140
>  - Throw NPE if duration is null
>  - 8267140

src/java.net.http/share/classes/java/net/http/HttpClient.java line 140:

> 138:  * connections, which it can typically reuse when another request is made to
> 139:  * the same origin server using the same protocol version and security,
> 140:  * through the same client. In the JDK implementation, connection pools

Hello Daniel, do you think we should maybe skip these details on how the connection pool decides to use a connection from pool? Perhaps, just make a mention that the HttpClient instance manages connections in a pool and may reuse it as and when necessary?

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PR: https://git.openjdk.org/jdk/pull/13019