Greengrass client devices last will (LWT) messages not firing

Question

We are using the Moquette broker (version 2.3.3) connecting a client device with the python SDK (awsiotsdk==1.11.8) via the following:

```
lwt = mqtt.Will(
                topic=self._greengrass_lifecycle_topic,
                qos=mqtt.QoS.AT_MOST_ONCE,
                payload=json.dumps({
                    'eventType': 'disconnected',
                    'clientId': self._iot_device._config.thing_name
                }).encode('utf-8'),
                retain=False
            )

mqtt_connection = mqtt_connection_builder.mtls_from_path(
                    endpoint=endpoint,
                    port=port,
                    cert_filepath=self._iot_device._device_cert_path,
                    pri_key_filepath=self._iot_device._device_key_path,
                    client_bootstrap=client_bootstrap,
                    ca_filepath=root_ca_path,
                    client_id=self._iot_device._config.thing_name,
                    clean_session=False,
                    keep_alive_secs=6,
                    will=lwt,
                    on_connection_interrupted=self.on_connection_interrupted,
                    on_connection_resumed=self.on_connection_resumed)
                connected_future = mqtt_connection.connect()
```

Client connect and graceful disconnect (power down, kill process) works as-expected, but when we pull the Ethernet cord of our IoT thing the LWT message never fires.

I have tried using QoS=2 but it still doesn't fire. The documentation seems to say that all of this should be supported (https://docs.aws.amazon.com/greengrass/v2/developerguide/mqtt-broker-moquette-component.html)

Any idea why this isn't working?

Accepted Answer

After updating to the latest Nucleus and client libraries we are no longer seeing this issue. Closing.

Answer

How long are you waiting for LWT message?  Do you have other keep-alive settings, etc, set?   I just performed a an experiement where I blocked port 8883 from a client and LWT was sent sometime after

Answer

Hi. Are you trying to get the LWT received at AWS IoT Core? Or just by other clients connected to the Moquette broker?

If the former, then you need to have setup the MQTT Bridge config for the LWT topic, as you perhaps already know.

Greengrass client devices last will (LWT) messages not firing

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