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feat: Add critical broker data retrieval bug detection logging

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Phase 4.5: Root Cause Identified - Broker-Side Bug

Added detailed logging to detect when broker returns 0 messages despite HWM indicating data exists:
  - CRITICAL BUG log when broker returns empty but HWM > requestedOffset
  - Logs broker metadata (logStart, nextOffset, endOfPartition)
  - Per-message logging for debugging

Changes:
  - broker_client_fetch.go: Added CRITICAL BUG detection and logging

Test Results:
  - 87.9% delivery (2067/2350) - consistent with previous
  - Confirmed broker bug: Returns 0 messages for offset 1424 when HWM=1428

Root Cause Discovered:
  ✅ Gateway fetch logic is CORRECT
  ✅ HWM calculation is CORRECT
  ❌ Broker's ReadMessagesAtOffset or disk read function FAILING SILENTLY

Evidence:
  Multiple CRITICAL BUG logs show broker can't retrieve data that exists:
    - topic-3[0] offset 1424 (HWM=1428)
    - topic-2[0] offset 968 (HWM=969)

Answer to 'Why does stream stop?':
  1. Broker can't retrieve data from storage for certain offsets
  2. Gateway gets empty responses repeatedly
  3. Sarama gives up thinking no more data
  4. Channel closes cleanly (not a crash)

Next: Investigate broker's ReadMessagesAtOffset and disk read path
This commit is contained in:
chrislu
2025-10-17 12:07:48 -07:00
parent f66960e445
commit be247ae497
2 changed files with 24 additions and 10 deletions
Download Patch File Download Diff File Expand all files Collapse all files

18
weed/mq/kafka/integration/broker_client_fetch.go
View File

@@ -80,8 +80,18 @@ func (bc *BrokerClient) FetchMessagesStateless(ctx context.Context, topic string
}
}
glog.V(3).Infof("[FETCH-STATELESS-CLIENT] Received %d messages from broker, nextOffset=%d, hwm=%d",
len(resp.Messages), resp.NextOffset, resp.HighWaterMark)
// CRITICAL DEBUGGING: Log what broker returned
glog.Infof("[FETCH-STATELESS-CLIENT] Broker response for %s[%d] offset %d: messages=%d, nextOffset=%d, hwm=%d, logStart=%d, endOfPartition=%v",
topic, partition, startOffset, len(resp.Messages), resp.NextOffset, resp.HighWaterMark, resp.LogStartOffset, resp.EndOfPartition)
// CRITICAL: If broker returns 0 messages but hwm > startOffset, something is wrong
if len(resp.Messages) == 0 && resp.HighWaterMark > startOffset {
glog.Errorf("[FETCH-STATELESS-CLIENT] CRITICAL BUG: Broker returned 0 messages for %s[%d] offset %d, but HWM=%d (should have %d messages available)",
topic, partition, startOffset, resp.HighWaterMark, resp.HighWaterMark-startOffset)
glog.Errorf("[FETCH-STATELESS-CLIENT] This suggests broker's FetchMessage RPC is not returning data that exists!")
glog.Errorf("[FETCH-STATELESS-CLIENT] Broker metadata: logStart=%d, nextOffset=%d, endOfPartition=%v",
resp.LogStartOffset, resp.NextOffset, resp.EndOfPartition)
}
// Convert protobuf messages to SeaweedRecord
records := make([]*SeaweedRecord, 0, len(resp.Messages))
@@ -93,6 +103,10 @@ func (bc *BrokerClient) FetchMessagesStateless(ctx context.Context, topic string
Offset: startOffset + int64(i), // Sequential offset assignment
}
records = append(records, record)
// Log each message for debugging
glog.V(4).Infof("[FETCH-STATELESS-CLIENT] Message %d: offset=%d, keyLen=%d, valueLen=%d",
i, record.Offset, len(msg.Key), len(msg.Value))
}
if len(records) > 0 {