[I] [Bug] Unexpected decrement of lmq counter [rocketmq]

["imzs (via GitHub)" <gi...@apache.org>]

imzs opened a new issue, #10453:
URL: https://github.com/apache/rocketmq/issues/10453

   ### Before Creating the Bug Report
   
   - [x] I found a bug, not just asking a question, which should be created in [GitHub Discussions](https://github.com/apache/rocketmq/discussions).
   
   - [x] I have searched the [GitHub Issues](https://github.com/apache/rocketmq/issues) and [GitHub Discussions](https://github.com/apache/rocketmq/discussions)  of this repository and believe that this is not a duplicate.
   
   - [x] I have confirmed that this bug belongs to the current repository, not other repositories of RocketMQ.
   
   
   ### Runtime platform environment
   
   .
   
   ### RocketMQ version
   
   .
   
   ### JDK Version
   
   .
   
   ### Describe the Bug
   
   We previously implemented an LMQ counting mechanism and have now discovered an unexpected counter underflow issue in RocksDBConsumeQueueOffsetTable.
   
   ### Steps to Reproduce
   
   When specific get* operation is called for a non-existent LMQ topic, a sentinel value -1L is placed into topicQueueMaxCqOffset without incrementing lmqCounter. However, if this topic is later deleted, removeHeapMaxCqOffset unconditionally decrements lmqCounter, causing the counter to underflow.
   
   ### What Did You Expect to See?
   
   lmqCounter should not be decremented for entries that were never actually counted.
   
   ### What Did You See Instead?
   
   .
   
   ### Additional Context
   
   .


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Re: [I] [Bug] Unexpected decrement of lmq counter [rocketmq]

["oss-sentinel-ai (via GitHub)" <gi...@apache.org>]

oss-sentinel-ai commented on issue #10453:
URL: https://github.com/apache/rocketmq/issues/10453#issuecomment-4656296174

   ## Assessment by github-manager-bot
   
   **Classification:** 🐛 Bug
   
   ### Summary
   The issue reports an LMQ counter underflow bug in `RocksDBConsumeQueueOffsetTable`:
   - When a `get*` operation is called for a non-existent LMQ topic, a sentinel value `-1L` is placed into `topicQueueMaxCqOffset` **without incrementing `lmqCounter`**
   - When this topic is later deleted, `removeHelperTopic` decrements `lmqCounter`, causing an unexpected underflow
   
   ### Analysis
   This is a valid bug report from a known contributor. The issue describes a specific code path where:
   1. **Creation path**: Non-existent topic lookup → sentinel value inserted → counter NOT incremented
   2. **Deletion path**: Topic deleted → counter decremented → **underflow**
   
   This is a classic counter mismatch bug that can lead to incorrect LMQ topic counts.
   
   ### Recommendation
   ✅ **Valid bug.** The root cause is clear: the sentinel value insertion path doesn't maintain the counter invariant. A fix should either:
   - Increment `lmqCounter` when inserting the sentinel value, OR
   - Track sentinel entries separately and skip counter decrement for them during deletion
   
   This requires maintainer review to confirm the fix approach.
   
   ---
   *Automated assessment by github-manager-bot*


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Re: [I] [Bug] Unexpected decrement of lmq counter [rocketmq]

["RockteMQ-AI (via GitHub)" <gi...@apache.org>]

RockteMQ-AI commented on issue #10453:
URL: https://github.com/apache/rocketmq/issues/10453#issuecomment-4689070789

   **Issue Evaluation**
   
   Category: `type/bug` | Status: **Needs Verification**
   
   Thank you for reporting this issue. To proceed with verification, please provide:
   - [ ] Version/tag or commit hash where this occurs
   - [ ] Steps to reproduce
   - [ ] Expected vs actual behavior
   - [ ] Relevant logs or stack traces
   
   ---
   *Automated evaluation by RockteMQ-AI*
   


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