Publish doesn't wait when QOS1

[YannickRiou]

Describe the bug

The publish function isn't pushing data to AWS after connection is recovered

Name: awscrt
Version: 0.5.13
Home-page: https://github.com/awslabs/aws-crt-python

Name: AWSIoTPythonSDK
Version: 1.4.7
Home-page: https://github.com/aws/aws-iot-device-sdk-python.git

Name: awsiotsdk
Version: 1.0.6
Home-page: https://github.com/aws/aws-iot-device-sdk-python-v2

Expected Behavior

When connection is lost, and a publish (with QOS1) was done and not successful, it should try to resend the message automatically (as QOS1 statement).

Current Behavior

When connection is lost, the publish send back a state pending about the data to be sent, but then when the device shutdown, the message hasn't been send at all.

Reproduction Steps

Connect with :

        event_loop_group = io.EventLoopGroup(1)
        host_resolver = io.DefaultHostResolver(event_loop_group)
        client_bootstrap = io.ClientBootstrap(event_loop_group, host_resolver)

        self.mqtt_connection = mqtt_connection_builder.mtls_from_path(
            endpoint=self.iot_endpoint,
            cert_filepath=self.cert_filepath,
            pri_key_filepath=self.pri_key_filepath,
            client_bootstrap=client_bootstrap,
            ca_filepath=self.ca_filepath,
            on_connection_interrupted=self.on_connection_interrupted,
            on_connection_resumed=self.on_connection_resumed,
            client_id=self.client_id,
            clean_session=False,
            keep_alive_secs=30
        )

        logging.debug(" Connecting to {} with client ID '{}'...".format(self.iot_endpoint, self.client_id))
        
        connect_future = self.mqtt_connection.connect()

   # Future.result() waits until a result is available
        try:
            connect_future.result()        
            logging.debug(" Connected!")
        except Exception as e:
            print(e)
            return False

Publish with :

  logging.debug(" Publishing message to topic '{}': {}".format(topic, message))
        ret = self.mqtt_connection.publish(
            topic=topic,
            payload=message,
            qos=mqtt.QoS.AT_LEAST_ONCE)
        logging.debug(" Value returned by publish is ['{}']".format(str(ret)))

Possible Solution

The loop handling the resend of message (due to QOS1) is not working properly

Additional Information/Context

No response

SDK version used

1.0.6

Environment details (OS name and version, etc.)

Raspberry pi Zero - Raspbian Buster - Linux - 5.10.52+ #1440

[jmklix]

How often does this happen? and how long are you disconnected for? You do have clean_session set to false which is what you want when you want to publish messages after reconnecting. But I'm not sure why the publishes aren't happening.

Can you also attach logs from when this is happening?

[YannickRiou]

It happens everytime the network is down during publish. It is a cellular network so it might be down for a few seconds or more, it depends.
We verified on AWS logs and we see the connection of the device, and it's disconnection but no message coming from it in between. So it seems the MQTT message queue is filled waiting to be send but the network never comes up, the device shuts down and the message are lost.
Is there a solution to see the message queue with the SDK ?

[jmklix]

There is no way to see what messages are in the SDK queue.

Is the device successfully reconnecting? There is an backoff for when this SDK in retrying to publish messages. Adding the logs would help us better understand what might be happening.

[github-actions]

Greetings! It looks like this issue hasn’t been active in longer than a week. We encourage you to check if this is still an issue in the latest release. Because it has been longer than a week since the last update on this, and in the absence of more information, we will be closing this issue soon. If you find that this is still a problem, please feel free to provide a comment or add an upvote to prevent automatic closure, or if the issue is already closed, please feel free to open a new one.