[improve][broker] Enhance logging for subscription creation failures due to NotAllowedException

[coderzc]

Motivation

2025-12-05T11:02:37,446+0000 [ForkJoinPool.commonPool-worker-2] ERROR org.apache.pulsar.broker.service.persistent.PersistentTopic - [persistent://pe/lab/result_pb-partition-1] Failed to create subscription: rw-consumer-855-7985
java.util.concurrent.CompletionException: org.apache.pulsar.broker.service.BrokerServiceException$NotAllowedException: Durable subscription with the same name already exists.

Modifications

Change log level form ERROR to Warn for NotAllowedException

Verifying this change

• Make sure that the change passes the CI checks.

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

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

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This change added tests and can be verified as follows:

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• 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

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Matching PR in forked repository

PR in forked repository:

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- [ ] `doc` <!-- Your PR contains doc changes -->
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[Technoboy-]

is it possible to add a test?

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 74.45%. Comparing base (270120c) to head (4938e22).
⚠️ Report is 39 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #25064      +/-   ##
============================================
- Coverage     74.48%   74.45%   -0.04%     
+ Complexity    34186    34051     -135     
============================================
  Files          1921     1899      -22     
  Lines        150376   149711     -665     
  Branches      17469    17403      -66     
============================================
- Hits         112005   111462     -543     
+ Misses        29499    29372     -127     
- Partials       8872     8877       +5     

Flag	Coverage Δ
inttests	26.35% <0.00%> (+<0.01%)	⬆️
systests	22.98% <0.00%> (+0.06%)	⬆️
unittests	73.99% <100.00%> (-0.03%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
...sar/broker/service/persistent/PersistentTopic.java	80.33% <100.00%> (+0.29%)	⬆️

... and 137 files with indirect coverage changes

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