[fix][broker] Fix get topic policies as null during clean cache

[coderzc]

Motivation

Currently, we may get topic policies as null during the clean topic policies since there is a race condition between them.

time	thread1 getTopicPolicies	thread2 cleanCacheAndCloseReader
t1	check if policyCacheInitMap exists the value of this namespace	remove the reader of this namespace from readerCaches
t2	the value of this namespace in the policyCacheInitMap is true	remove the policies of this namespace from policiesCache
t3	gets the topicPolicies of this namespace from policiesCache as null
t4		remove the value of this namespace from policyCacheInitMap

Modifications

Use policyCacheInitMap.compute() to make get topic policies init flag and clean cache mutually exclusive.

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.

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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

Documentation

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Matching PR in forked repository

PR in forked repository:

[codelipenghui]

@coderzc Can you reproduce the issue with this test with the fix? I have tried it on my laptop without this fix. But can't reproduce the issue. The fix looks good, just the test can't protect the changes of this PR.

[coderzc]

I have rewritten the test to make it can reproduce the issue.

[coderzc]

@codelipenghui PTAL.

[mattisonchao]

can you delete the blank line?

[codecov-commenter]

Codecov Report

❌ Patch coverage is 92.85714% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 73.11%. Comparing base (0bac873) to head (eae2a70).
⚠️ Report is 1917 commits behind head on master.

Files with missing lines	Patch %	Lines
.../service/SystemTopicBasedTopicPoliciesService.java	92.85%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@              Coverage Diff              @@
##             master   #20763       +/-   ##
=============================================
+ Coverage     36.80%   73.11%   +36.31%     
- Complexity    12073    32128    +20055     
=============================================
  Files          1689     1866      +177     
  Lines        129387   139041     +9654     
  Branches      14120    15294     +1174     
=============================================
+ Hits          47619   101661    +54042     
+ Misses        75482    29322    -46160     
- Partials       6286     8058     +1772     

Flag	Coverage Δ
inttests	24.17% <42.85%> (+0.08%)	⬆️
systests	25.01% <21.42%> (-0.11%)	⬇️
unittests	72.41% <92.85%> (+40.49%)	⬆️

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

Files with missing lines	Coverage Δ
.../service/SystemTopicBasedTopicPoliciesService.java	76.96% <92.85%> (+18.93%)	⬆️

... and 1431 files with indirect coverage changes

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