CloudWatch Events Metrics - DeadLetterInvocations accurate explanation with an example

Question

Hi, I did not find https://docs.aws.amazon.com/eventbridge/latest/userguide/eb-monitoring.html useful for the definition of DeadLetterInvocations. I tried searching on the internet, are these explanations correct? https://stackoverflow.com/questions/68426496/cloudwatch-events-metrics-deadletterinvocations

Also, is the following example correct?

> This has nothing to do with the SQS DLQ, but rather is about events that are not being handled by an event because it would result in an infinite loop. Imagine setting up Bus A and Bus B, in which Bus A has a rule that forwards events to Bus B, and Bus B has a rule that forwards it back to Bus A. That scenario is where you will see this metric present.

Leo K · Answer

The dead-letter queue in the context of EventBridge refers to the SQS queue to which your EventBridge rule is set to deliver messages that it was unable to deliver to the target configured for the EventBridge rule: https://docs.aws.amazon.com/eventbridge/latest/userguide/eb-rule-event-delivery.html#eb-rule-dlq

The statement you quoted about it not having anything to do with SQS is somewhat ambiguous, but the fact (and what the writer might also mean) is that if the target for your EventBridge rule is an SQS queue, that target queue will have its own DLQ, separate from the DLQ of your EventBridge rule. The target queue's DLQ will receive messages that failed to be delivered onwards from the target queue, whereas the DLQ you configure for the EventBridge rule target will receive the messages that EventBridge couldn't deliver to the target queue.

CloudWatch Events Metrics - DeadLetterInvocations accurate explanation with an example

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