[improve] [pip] PIP-364: Introduce a new load balance algorithm AvgShedder

[thetumbled]

Motivation

Implementation PR for PIP: https://github.com/apache/pulsar/pull/22946.

Modifications

• Introduce new algo: AvgShedder.
• provide a way to bind shedding strategy and placement strategy.

Verifying this change

• [ ] Make sure that the change passes the CI checks.

(Please pick either of the following options)

This change added tests and can be verified as follows:

(example:)

• Added integration tests for end-to-end deployment with large payloads (10MB)
• Extended integration test for recovery after broker failure

Does this pull request potentially affect one of the following parts:

If the box was checked, please highlight the changes

• [ ] Dependencies (add or upgrade a dependency)
• [ ] The public API
• [ ] The schema
• [ ] The default values of configurations
• [ ] The threading model
• [ ] The binary protocol
• [ ] The REST endpoints
• [ ] The admin CLI options
• [ ] The metrics
• [ ] Anything that affects deployment

Documentation

• [ ] doc
• [x] doc-required
• [ ] doc-not-needed
• [ ] doc-complete

Matching PR in forked repository

PR in forked repository: https://github.com/thetumbled/pulsar/pull/59

[github-actions[bot]]

@thetumbled Please add the following content to your PR description and select a checkbox:

- [ ] `doc` <!-- Your PR contains doc changes -->
- [ ] `doc-required` <!-- Your PR changes impact docs and you will update later -->
- [ ] `doc-not-needed` <!-- Your PR changes do not impact docs -->
- [ ] `doc-complete` <!-- Docs have been already added -->

[thetumbled]

As the proposal PR has been merged, we can proceed with the implementation PR, thanks. @lhotari @heesung-sn @Demogorgon314 @BewareMyPower @poorbarcode

[thetumbled]

Besides, the findBundlesForUnloading method is too long (about 200 lines), which is hard to read. It's worth splitting it into multiple private methods. From what I see, there should be 3 steps:

1. loadData.getBrokerData() -> updated brokerScoreMap (Map<String, Double>) and its sorted keys according to the value comparation
2. Update brokerHitCountForLow and brokerHitCountForHigh according to the threshold related configs.
3. Update and return selectedBundlesCache according to loadData.getRecentlyUnloadedBundles() and the two maps above.

Updated, thanks for review!

[thetumbled]

Good job! Can you add the AvgShedder algorithm for ExtensibleLoadManager.

Sounds good, i will try to acheive that.

[thetumbled]

PIP-364: Introduce a new load balance algorithm AvgShedder

[Demogorgon314]

Hi @thetumbled, can you help send a discussion to cherry-pick this new algorithm into branch-3.0, branch-3.2, and branch-3.3?

[thetumbled]

Hi @thetumbled, can you help send a discussion to cherry-pick this new algorithm into branch-3.0, branch-3.2, and branch-3.3?

discussion link: https://lists.apache.org/thread/9yqq8wky1k73hqz6xhvstk6x0ycknqgt

[thetumbled]

Tip: If you want to cherry pick this pr, please cherry pick this patch too: https://github.com/apache/pulsar/pull/23156