IoT broker: Publish mqtt messages with messageExpiry doesn't seem to work

Question

I'm using [boto3](https://boto3.amazonaws.com/v1/documentation/api/latest/reference/services/iot-data/client/publish.html#publish) to publish messages to some mqtt topic. I've tried both approaches retain=True and retain=False messages with a generally low value for `messageExpiry` (initially 10 seconds and then 1, 60, 120, and other values in case that was the issue) but it doesn't seem to work.

With `retain=True` I'd expect the message to expire and delete itself after `messageExpiry`seconds, but it doesn't (a client connecting after the publish does receive the message, of course). With `retain=False` I would expect a client that connects a few seconds after the publish operation (but before `messageExpiry` seconds) to receive the published message, but it doesn't.

So not sure if I'm missing some configuration, messageExpiry doesn't work as I would expect (though according to the table from https://docs.aws.amazon.com/iot/latest/developerguide/mqtt.html#mqtt5 it should work) or I'm doing something wrong.

Accepted Answer

When the original question was posted they weren't working. They do work **now** as expected.

Answer

Hi jesusgs. I concur with your findings. In using either **boto3** or the **AWS CLI**, I find that the `messageExpiry` parameter isn't working. Conversely, if I publish using the MQTT test client in AWS IoT Core, it does work.

I'm of the (perhaps mistaken) belief it's an issue on our side with the IoT data plane HTTP Publish operation. I've raised it internally and will post back here when I know more.

Answer

`messageExpiry` and `retain` flags work as of 2023-08-01 with boto3 and with the PUBLISH API

https://boto3.amazonaws.com/v1/documentation/api/latest/reference/services/iot-data/client/publish.html

https://docs.aws.amazon.com/iot/latest/apireference/API_iotdata_Publish.html

IoT broker: Publish mqtt messages with messageExpiry doesn't seem to work

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