Messages published over MQTT from an IoT Greengrass device arrive out-of-order


Hi, when using IoT Greengrass I've found that when MQTT messages are published close together (less than 1-second interval) they may arrive out of order. Is this expected?

asked 4 years ago601 views
1 Answer
Accepted Answer

Out-of-order MQTT messages should be expected and solutions should be designed with this principle in mind. Messages published with QoS1 retries from the client when ACK is not received is a common way that messages get out of order. Many things can cause the ACK to not be received - Internet down, power outage, network congestion.

Strategies for handling out-of-order messages include use of sequencing numbers generated by the client and ignoring messages received with a timestamp older than the last processed message. For more guidance, consult the IoT Lens for AWS Well-Architected.

answered 4 years ago

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