Static topic mapping may select a stale epoch when the epoch delta overflows

[yuluo-yx]

Description

Static topic mapping sorts long epoch values by subtracting them and narrowing the result to int. When two epochs differ by more than Integer.MAX_VALUE, the comparator can reverse their order. In replacement mode, checkAndBuildMappingItems then keeps the stale broker mapping instead of the latest one.

Expected behavior

Epochs should be ordered with Long.compare so the newest mapping always wins without arithmetic overflow.

Reproduction

Create two mapping details for the same logical queue with epochs 0 and Long.MAX_VALUE, call checkAndBuildMappingItems with replace enabled, and observe that the epoch-0 mapping is selected.

[RockteMQ-AI]

Issue Evaluation

Category: type/bug | Status: Confirmed

The issue is valid. Static topic mapping sorts long epoch values by subtracting and narrowing to int. When two epochs differ by more than Integer.MAX_VALUE, the comparator reverses their order. In replacement mode, checkAndBuildMappingItems keeps the stale broker mapping instead of the latest.

Root Cause: (int)(a - b) comparator pattern on long epoch values.
Impact: Static topic — stale mapping can be selected, routing messages to wrong/outdated brokers.
Severity: medium-high

Recommended fix: Replace with Long.compare(a, b) for overflow-safe epoch ordering.

An automated fix proposal can be generated. Reply /approve to proceed with PR generation.

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Automated evaluation by RockteMQ-AI