[PR] [fix] keep zero-row metrics data in redis queue codec [hertzbeat]

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

orangeCatDeveloper opened a new pull request, #4305:
URL: https://github.com/apache/hertzbeat/pull/4305

   ## What's changed?
   
   Fixes #3457.
   
   With the Redis data queue enabled, a monitor whose target goes offline never turns DOWN. The collector does report the failure: it emits a `MetricsData` with zero rows whose code (`TIMEOUT`/`FAIL`), monitor id and priority all live in the Arrow schema metadata. But `RedisMetricsDataCodec.decodeValue` treated `rowCount == 0` as an empty message and dropped it, so `DataStorageDispatch.calculateMonitorStatus` never saw the failure and the monitor stayed UP forever. The in-memory and Kafka queues do not filter zero-row data, so only Redis deployments were affected.
   
   This change stops discarding zero-row messages and instead rejects only streams that contain no record batch at all (`loadNextBatch()` returning false), which our encoder never produces. Downstream is safe: history and realtime writers already reject non-SUCCESS data, so failure messages only drive status/alerting.
   
   Verified end-to-end with a Redis-queue deployment (app + redis + nginx target in docker): before the fix the monitor stays UP forever after the target is stopped; with the fix it flips to DOWN within one collect cycle.
   
   ## Checklist
   
   - [x]  I have read the [Contributing Guide](https://hertzbeat.apache.org/docs/community/code_style_and_quality_guide)
   - [x]  I have written the necessary doc or comment.
   - [x]  I have added the necessary unit tests and all cases have passed.
   
   ## Add or update API
   
   - [ ] I have added the necessary [e2e tests](https://github.com/apache/hertzbeat/tree/master/e2e) and all cases have passed.
   


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Re: [PR] [fix] keep zero-row metrics data in redis queue codec [hertzbeat]

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

Duansg merged PR #4305:
URL: https://github.com/apache/hertzbeat/pull/4305


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