[Bug] Unexpected decrement of lmq counter

[imzs]

Before Creating the Bug Report

• I found a bug, not just asking a question, which should be created in GitHub Discussions.

• I have searched the GitHub Issues and GitHub Discussions of this repository and believe that this is not a duplicate.

• 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

.

[oss-sentinel-ai]

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

[RockteMQ-AI]

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