8371475: HttpClient: Implement CUBIC congestion controller

[djelinski]

CUBIC is a standard TCP congestion control algorithm that uses a cubic function instead of a linear congestion window increase function to improve scalability and stability over fast and long-distance networks. CUBIC has been adopted as the default TCP congestion control algorithm by the Linux, Windows, and Apple stacks.

This PR adds a new congestion controller algorithm. It reuses a large part of the QuicRenoCongestionController, which was refactored to two classes - QuicBaseCongestionController, containing the shared code, and QuicRenoCongestionController, containing only the code that is unique to Reno.

CUBIC is now the default congestion controller. Reno can still be selected by setting the system property jdk.httpclient.quic.congestionController to reno.

A new test was added to exercise the new congestion controller. Existing tests continue to pass.

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Progress

• Change must be properly reviewed (1 review required, with at least 1 Reviewer)
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Issue

• JDK-8371475: HttpClient: Implement CUBIC congestion controller (Enhancement - P4)

Reviewers

• Daniel Fuchs (@dfuch - Reviewer) 🔄 Re-review required (review applies to 2b47732e)

Reviewing

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[bridgekeeper]

👋 Welcome back djelinski! A progress list of the required criteria for merging this PR into pr/28156 will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

[openjdk]

@djelinski This change is no longer ready for integration - check the PR body for details.

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[mlbridge]

Webrevs

• 05: Full - Incremental (60680962)
• 04: Full - Incremental (2b47732e)
• 03: Full - Incremental (32160ef9)
• 02: Full (195b0f89)
• 01: Full - Incremental (b95950f2)
• 00: Full (b95950f2)

[AlanBateman]

If jdk.httpclient.quic.congestionController is exposed then we'll need to track this with a CSR.

[vy]

Really neat work @djelinski! I liked the surgery you carried out in QuicBaseCC. 💯

I've dropped some minor remarks. I guess we will need some time to wrap our mind around the math involved in the PR.

[openjdk-notifier]

The parent pull request that this pull request depends on has now been integrated and the target branch of this pull request has been updated. This means that changes from the dependent pull request can start to show up as belonging to this pull request, which may be confusing for reviewers. To remedy this situation, simply merge the latest changes from the new target branch into this pull request by running commands similar to these in the local repository for your personal fork:

git checkout quic-cubic
git fetch https://git.openjdk.org/jdk.git master
git merge FETCH_HEAD
# if there are conflicts, follow the instructions given by git merge
git commit -m "Merge master"
git push

[openjdk]

@djelinski this pull request can not be integrated into master due to one or more merge conflicts. To resolve these merge conflicts and update this pull request you can run the following commands in the local repository for your personal fork:

git checkout quic-cubic
git fetch https://git.openjdk.org/jdk.git master
git merge FETCH_HEAD
# resolve conflicts and follow the instructions given by git merge
git commit -m "Merge master"
git push

[djelinski]

Thanks @AlanBateman @vy for the reviews.

The property was not meant to be exposed; IMO CUBIC is superior to Reno in all aspects that matter. I renamed it to include internal.

We will probably need to revisit the configuration if and when we implement BBR, but we aren't quite there yet.

[dfuch]

And another question: after this change - do we still have tests for the Reno congestion controller? Or is everthing using Cubic?

[djelinski]

Thanks @dfuch for the review.

We didn't have any Reno-specific tests. I modified a few of the existing tests to also run with Reno now.

[dfuch]

New changes look good to me. Please make sure tests remain stable before integrating.