Dead Letter Queue Workflow

patterns

Dead letter queue pattern for handling failed messages with retry exhaustion detection, DLQ routing, manual inspection, and reprocessing capability.

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Full FlowZap Code

MainQueue { # Main Queue
n1: circle label:"Start"
n2: rectangle label:"Receive message"
n3: rectangle label:"Attempt processing"
n4: diamond label:"Processing successful?"
n5: rectangle label:"Acknowledge message"
n6: rectangle label:"Increment retry count"
n7: circle label:"End"
n1.handle(right) -> n2.handle(left)
n2.handle(right) -> n3.handle(left)
n3.handle(right) -> n4.handle(left)
n4.handle(right) -> n5.handle(left) [label="Yes"]
n4.handle(bottom) -> n6.handle(top) [label="No"]
n5.handle(right) -> n7.handle(left)
n6.handle(bottom) -> RetryLogic.n8.handle(top) [label="Check retries"]
}
RetryLogic { # Retry Logic
n8: diamond label:"Max retries exceeded?"
n9: rectangle label:"Wait with backoff"
n10: rectangle label:"Requeue message"
n11: rectangle label:"Move to DLQ"
n8.handle(right) -> n9.handle(left) [label="No"]
n8.handle(bottom) -> n11.handle(top) [label="Yes"]
n9.handle(right) -> n10.handle(left)
n10.handle(top) -> MainQueue.n3.handle(bottom) [label="Retry"]
n11.handle(bottom) -> DeadLetterQueue.n12.handle(top) [label="Failed"]
}
DeadLetterQueue { # Dead Letter Queue
n12: rectangle label:"Store failed message"
n13: rectangle label:"Log failure details"
n14: rectangle label:"Send alert notification"
n15: rectangle label:"Await manual review"
n16: diamond label:"Reprocess or discard?"
n17: rectangle label:"Move back to main queue"
n18: rectangle label:"Archive and delete"
n12.handle(right) -> n13.handle(left)
n13.handle(right) -> n14.handle(left)
n14.handle(right) -> n15.handle(left)
n15.handle(right) -> n16.handle(left)
n16.handle(right) -> n17.handle(left) [label="Reprocess"]
n16.handle(bottom) -> n18.handle(top) [label="Discard"]
n17.handle(top) -> MainQueue.n2.handle(bottom) [label="Retry"]
n18.handle(top) -> MainQueue.n7.handle(bottom) [label="Discarded"]
}