RFR: 8371475: HttpClient: Implement CUBIC congestion controller [v3]

[Daniel Jeliński]

On Fri, 14 Nov 2025 12:18:19 GMT, Daniel Fuchs <dfuchs at openjdk.org> wrote:

>> Daniel Jeliński has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 24 commits:
>> 
>>  - Update test comments
>>  - Convert CubicTest to JUnit
>>  - Merge declaration and assignment
>>  - More aggressive target growth
>>  - Merge remote-tracking branch 'origin/master' into quic-cubic
>>  - Make classes final
>>  - Rename system property to internal
>>  - Add a system property to select congestion controller
>>  - Implement fast convergence
>>  - Add comments
>>  - ... and 14 more: https://git.openjdk.org/jdk/compare/1f1f7bb4...195b0f89
>
> src/java.net.http/share/classes/jdk/internal/net/http/quic/QuicBaseCongestionController.java line 69:
> 
>> 67:     protected long maxBytesInFlight;
>> 68:     protected Deadline congestionRecoveryStartTime;
>> 69:     protected long ssThresh = Long.MAX_VALUE;
> 
> Can we remove the `protected` keyword on the mutable fields? All the subclasses are in the same package.

Done.

> src/java.net.http/share/classes/jdk/internal/net/http/quic/QuicBaseCongestionController.java line 84:
> 
>> 82:         this.timeSource = source;
>> 83:         this.pacer = new QuicPacer(rttEstimator, this);
>> 84:     }
> 
> Suggestion:
> 
>     protected QuicBaseCongestionController(String dbgTag, QuicRttEstimator rttEstimator) {
>         this(dbgTag, TimeSource.source(), rttEstimator);
>     }
> 
>     // Allows to pass a custom TimeLine when testing
>     QuicBaseCongestionController(String dbgTag, TimeLine source, QuicRttEstimator rttEstimator) {
>         this.dbgTag = dbgTag;
>         this.timeSource = source;
>         this.pacer = new QuicPacer(rttEstimator, this);
>     }

Done.

> src/java.net.http/share/classes/jdk/internal/net/http/quic/QuicCubicCongestionController.java line 124:
> 
>> 122:             // not sure if dblTarget can overflow a long, but 1.5 congestionWindow can not.
>> 123:             if (dblTargetBytes > 1.5 * congestionWindow) {
>> 124:                 targetBytes = (long) (1.5 * congestionWindow);
> 
> Suggestion:
> 
>             // targetLimit is 1.5 * congestionWindow
>             long targetLimit = congestionWindow + (congestionWindow >> 1)
>             if (dblTargetBytes > targetLimit) {
>                 targetBytes = targetLimit;

Refactored the code, I think it's easier to follow now.

-------------

PR Review Comment: https://git.openjdk.org/jdk/pull/28195#discussion_r2549245195
PR Review Comment: https://git.openjdk.org/jdk/pull/28195#discussion_r2549245648
PR Review Comment: https://git.openjdk.org/jdk/pull/28195#discussion_r2549248271