[ISSUE #10453] fix unexpected decrement of lmq counter

[imzs]

#10453 fix unexpected decrement of lmq counter.

[oss-sentinel-ai]

Review by github-manager-bot

Summary

This PR fixes the LMQ counter underflow bug described in #10453. When a getMaxCqOffset call for a non-existent LMQ topic inserts a sentinel value -1L without incrementing lmqCounter, the subsequent deletion of that topic would incorrectly decrement the counter.

Findings

• [Good] RocksDBConsumeQueueOffsetTable.java:603-607 — The fix correctly checks prev != -1L before decrementing lmqCounter. This ensures the counter is only decremented for entries that were actually counted (i.e., had a real offset, not a sentinel).
• [Good] RocksDBConsumeQueueOffsetTable.java:606 — Added a warning log for the edge case where a sentinel entry is being removed. This aids debugging and monitoring.
• [Good] RocksDBConsumeQueueOffsetTableTest.java:149-160 — New test testLmqCounter_decrement correctly verifies:
  1. Getting max offset for a non-existent LMQ topic returns null without incrementing counter
  2. Destroying that offset does not decrement the counter (counter stays at initCount)
• [Good] Test setup properly adds required mocks (columnFamilyHandle, messageStoreConfig) for the updated constructor.

Analysis

The fix is minimal, targeted, and correct:

• The root cause is a counter invariant violation: sentinel value insertion doesn't increment, but deletion decrements
• The fix restores the invariant by checking the sentinel value before decrementing
• No backward compatibility concerns — this is a pure bug fix

Verdict

✅ Approved — Clean, minimal fix with proper test coverage for the counter underflow bug.

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Automated review by github-manager-bot

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 48.02%. Comparing base (ef6a8c9) to head (7b8a041).

Additional details and impacted files

@@              Coverage Diff              @@
##             develop   #10454      +/-   ##
=============================================
- Coverage      48.07%   48.02%   -0.06%     
+ Complexity     13312    13301      -11     
=============================================
  Files           1377     1377              
  Lines         100632   100634       +2     
  Branches       12995    12996       +1     
=============================================
- Hits           48378    48328      -50     
- Misses         46327    46363      +36     
- Partials        5927     5943      +16     

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