elephone-184 opened a new pull request, #4973:
URL: https://github.com/apache/rocketmq-dashboard/pull/4973
## What is the purpose of the change
When administrators downscale topic partition queues (e.g. from 16 queues
down to 8 queues), any queues with `queueId >= targetQueueNum` are immediately
cut off from client publishing and routing. If these truncated queues still
hold unconsumed messages, those messages become silently stranded until queues
are re-expanded, potentially causing data lag, consumer starvation, or business
SLA violations.
This PR introduces an automated `TopicQueueShrinkGuardEngine`:
1. `TopicShrinkPrecheckVO`: Domain report capturing `safeToShrink`, total
unconsumed messages on truncated queues, per-queue risk ratings (`CRITICAL`,
`HIGH`, `LOW`), and step-by-step graceful migration guidance.
2. `TopicQueueShrinkGuardEngine`: Cross-references live `TopicQueueStatsVO`
min/max offsets across all brokers against the proposed `targetQueueNum`. It
detects stranded backlog, computes risk severity, and recommends an automated
3-phase drainage pipeline (writeQueue reduction -> consumer catch-up ->
readQueue finalization).
3. Controller & Service wiring: Integrates through
`MetadataService.precheckTopicQueueShrink` and exposes
`/api/topics/{name}/precheck-shrink` in `TopicController`.
4. Comprehensive unit test suite covering expansion no-ops, zero-backlog
safe shrinks, dangerous backlog detection across multiple brokers, and
service/controller tests.
## Brief changelog
- Add `TopicShrinkPrecheckVO.java` domain model.
- Add `TopicQueueShrinkGuardEngine.java` evaluation logic.
- Add `precheckTopicQueueShrink` in `MetadataService` and
`/api/topics/{name}/precheck-shrink` in `TopicController`.
- Add `TopicQueueShrinkGuardEngineTest.java` and expand
`MetadataServiceTest.java` and `TopicControllerTest.java`.
## Verifying this change
- `TopicQueueShrinkGuardEngineTest`: verifies expansion handling, invalid
queue counts, zero backlog scenarios, and multi-broker queue truncation risks.
- `MetadataServiceTest`: verifies integration with topic metadata resolution.
- `TopicControllerTest`: verifies `/api/topics/{name}/precheck-shrink` REST
endpoint mapping.
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