`ClientRequestContext#cancel` cancels the associated request immediately

[jrhee17]

Motivation:

In order to handle https://github.com/line/armeria/issues/4591, I propose that we first define an API which allows users to cancel a request. Currently, ClientRequestContext#cancel is invoked once CancellationScheduler#start is invoked. I propose to change the behavior of ClientRequestContext#cancel such that the associated request is aborted immediately. Once this API is available, it would be trivial to implement ResponseTimeoutMode by adjusting where to call CancellationScheduler#start. Additionally, users may easily implement their own timeout mechanism if they would like.

Modifications:

• CancellationScheduler related changes
  • DefaultCancellationScheduler is refactored to be lock based instead of event loop based. The reasoning for this change was for the scenario where the request execution didn't reach the event loop yet. i.e. If a user calls ctx.cancel in the decorator, a connection shouldn't be opened.
  • e.g. https://github.com/line/armeria/blob/59aa40a59e1f1122716e70f9f1d6f1402a6aae0e/core/src/test/java/com/linecorp/armeria/client/ContextCancellationTest.java#L90-L116
  • CancellationScheduler#updateTask is introduced. This API updates the cancellation task if the scheduler isn't invoked yet. If the scheduler is invoked already, the cancellation task will be executed eventually. This API allows ctx.cancel to attempt cancellation depending on which stage the request is at. For instance, at the decorators only req.abort needs to be called but at the request write stage, the cancellation task may need to send a reset signal.
  • Misc. an infinite timeout is internally represented as Long.MAX_VALUE instead of 0
• AbstractHttpRequestHandler related changes
  • CancellationTask in AbstractHttpRequestHandler, HttpResponseWrapper, AbstractHttpResponseHandler is modified to be scheduled inside an event loop. The reasoning is that ctx.cancel, and hence CancellationTask#run can be invoked from any thread.
  • There is a higher chance of AbstractHttpRequestHandler calling fail or failAndReset multiple times. There is no point in doing so, so added a boolean flag failed for safety.
• HttpResponseWrapper related changes
  • The original intention of cancelTimeoutAndLog was to not log if the response is unexpected. Modified so that if the response is cancelled or the context is cancelled, no logging is done
  • There is probably no reason to not call close when a timeout occurs. Unified the fragmented logic of closing the HttpResponseWrapper.
• Found that DefaultRequestLog is completing futures with the context set on the event loop. We generally don't do this since we strictly validate against setting incorrect RequestContexts, so modified to use withoutContext.

Result:

• Users can call ClientRequestContext#cancel to cancel the ongoing request easily.
• https://github.com/line/armeria/pull/5793 can be prepared for

[github-actions[bot]]

🔍 Build Scan® (commit: cc8db8310b7dbe154cf4758d729ec59a29fc1ded)

Job name	Status	Build Scan®
build-self-hosted-unsafe-jdk-8	✅	https://ge.armeria.dev/s/xt4w6si3fxioe
build-self-hosted-unsafe-jdk-21-snapshot-blockhound	✅	https://ge.armeria.dev/s/j463lr36xrngm
build-self-hosted-unsafe-jdk-17-min-java-17-coverage	✅	https://ge.armeria.dev/s/z7akszkmjtlio
build-self-hosted-unsafe-jdk-17-min-java-11	✅	https://ge.armeria.dev/s/gk5ifs4ykwdgu
build-self-hosted-unsafe-jdk-17-leak	✅	https://ge.armeria.dev/s/jxkgdbss7mqgm
build-self-hosted-unsafe-jdk-11	✅	https://ge.armeria.dev/s/2junq5mszo5ga
build-macos-12-jdk-21	✅	https://ge.armeria.dev/s/ufve7p4hdlpuw

[ikhoon]

https://github.com/line/armeria/pull/5156 has been merged. Would you mind resolving the conflicts?

[ikhoon]

@jrhee17 Would you check the test failures?

ContextCancellationTest > cancel_beforeDelegate(TestInfo) FAILED
    java.lang.AssertionError: 
    Expecting empty but was: [[creqId=147071ed][http://127.0.0.1:34223/#GET]]
        at com.linecorp.armeria.client.ContextCancellationTest.validateCallbackChecks(ContextCancellationTest.java:289)
        at com.linecorp.armeria.client.ContextCancellationTest.cancel_beforeDelegate(ContextCancellationTest.java:115)

ContextCancellationTest > cancel_beforeConnection(TestInfo) FAILED
    java.lang.AssertionError: 
    Expecting empty but was: [[creqId=456bf5ae][http://foo.com:34223/#POST]]
        at com.linecorp.armeria.client.ContextCancellationTest.validateCallbackChecks(ContextCancellationTest.java:289)
        at com.linecorp.armeria.client.ContextCancellationTest.cancel_beforeConnection(ContextCancellationTest.java:153)

[jrhee17]

Let me go ahead and merge this PR since it's reliable passing the CI again, thanks for the review all 👍