[fix][broker] Handle flow_or_qps bundle split requests in ELM

[Denovo1998]

Motivation

Manual bundle split requests in the extensible load manager path can fail incorrectly when flow_or_qps_equally_divide is used. The broker was building the split option from the default configured algorithm instead of the algorithm requested by the admin API, which can trigger a ClassCastException. In addition, when flow_or_qps_equally_divide cannot
produce a valid split boundary, the extensible load manager path turns that no-op case into
a misleading Bundle ... not found under namespace error.

Modifications

• build BundleSplitOption from the requested split algorithm instead of the default broker configuration
• create FlowOrQpsEquallyDivideBundleSplitOption only when the actual requested algorithm is flow_or_qps_equally_divide
• handle the "no valid split boundary" case as a no-op in ExtensibleLoadManagerImpl instead of reporting Bundle ... not found under namespace
• keep the real bundle not found error path only for actual split-bundle lookup failures
• add an admin API regression test to verify FLOW_OR_QPS_EQUALLY_DIVIDE no longer fails when the default split algorithm is different
• add an extensible load manager regression test to verify the no-boundary case does not fail and leaves the bundle layout unchanged

Verifying this change

• Make sure that the change passes the CI checks.

(Please pick either of the following options)

This change is a trivial rework / code cleanup without any test coverage.

(or)

This change is already covered by existing tests, such as (please describe tests).

(or)

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

Documentation

• doc
• doc-required
• doc-not-needed
• doc-complete

Matching PR in forked repository

PR in forked repository: Denovo1998#25

[Copilot]

Pull request overview

Fixes manual namespace bundle split behavior when using the flow_or_qps_equally_divide algorithm, ensuring the requested algorithm drives option construction and making the extensible load manager (ELM) treat “no valid split boundary” as a successful no-op instead of a misleading “bundle not found” failure.

Changes:

• Build BundleSplitOption based on the requested split algorithm (avoids ClassCastException for flow_or_qps_equally_divide).
• In ELM split flow, treat “no valid boundary” as a no-op success and keep “bundle not found” only for real lookup failures.
• Add regression tests covering the requested-algorithm path and the ELM no-boundary no-op behavior.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
pulsar-broker/src/main/java/org/apache/pulsar/broker/namespace/NamespaceService.java	Constructs split options based on the requested algorithm (not default config), preventing incorrect option types.
pulsar-broker/src/main/java/org/apache/pulsar/broker/loadbalance/extensions/ExtensibleLoadManagerImpl.java	Adjusts ELM bundle split to no-op on empty/null boundaries and only error on actual split-bundle lookup failures.
pulsar-broker/src/test/java/org/apache/pulsar/broker/admin/AdminApiTest.java	Adds regression test ensuring FLOW_OR_QPS requested algorithm doesn’t fail when default algorithm differs.
pulsar-broker/src/test/java/org/apache/pulsar/broker/loadbalance/extensions/ExtensibleLoadManagerImplTest.java	Adds regression test ensuring ELM path no-valid-boundary case succeeds and leaves bundle layout unchanged.

[Denovo1998]

The current CI runs really fast. Still stable！