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Dead Letter Queue (DLQ)

A destination for messages that cannot be processed automatically. Messages are routed to the DLQ when:

  1. Sequence mismatch with MERGE_MANUAL strategy
  2. Processing failures after retry exhaustion
  3. Payload retrieval failures (external storage unavailable)
  4. Unrecoverable errors in handlers

DLQ Entry Types​

SequenceMismatchDetails​

message SequenceMismatchDetails {
  uint64 expected_sequence = 1;
  uint64 actual_sequence = 2;
  MergeStrategy merge_strategy = 3;
}

EventProcessingFailedDetails​

message EventProcessingFailedDetails {
  string error_message = 1;
  uint32 retry_count = 2;
  bool is_transient = 3;
}

PayloadRetrievalFailedDetails​

For claim-check pattern failures when external payload cannot be retrieved.

Topic Structure​

Per-domain DLQ topics: angzarr.dlq.{domain}

Resolution​

DLQ messages require manual intervention:

  1. Inspect the failed message and context
  2. Fix the underlying issue
  3. Resubmit or discard the message
  4. Update monitoring/alerting as needed