IoT Thing Retain messages callback returns false

[c-gc]

I'm testing out retain functionality

I confirm the policy associated with the IoT Thing has these policies for all resources

• iot:RetainPublish
• iot:ListRetainedMessages
• iot:GetRetainedMessage

Publishing with retain message ON

Received with False

Received message on topic 📩 device1/command at ⏰2023-05-30 21:02:39: b'{\n  "message": "Hello from AWS IoT console retained"\n}'
Retained value: False

Relevant code:

# Callback when the subscribed topic receives a message
def message_callback(topic, payload, dup, qos, retain, **kwargs):
    current_time = time.strftime("%Y-%m-%d %H:%M:%S", time.localtime())
    print("Received message on topic 📩 {} at ⏰{}: {}".format(topic, current_time, payload))
    print("Retained value: {}".format(retain))

# Connect to AWS IoT and subscribe to a topic
data_topic = "device1/data"
command_topic = "device1/command"

mqtt_connection.subscribe(topic = command_topic, qos = mqtt.QoS.AT_LEAST_ONCE, callback = message_callback)

[bretambrose]

Can you attach DEBUG level logs from the SDK: https://github.com/awslabs/aws-crt-python/blob/main/awscrt/io.py#L28

[c-gc]

Interestingly when I retried today, it seems to work correctly. Not sure what changed. Closing the discussion as its no longer reproducible.

[MikeDombo]

Note that the retain flag is only set for retained messages which are sent upon first subscription.

https://docs.aws.amazon.com/iot/latest/developerguide/mqtt.html#mqtt-retain:~:text=Retained%20messages%20received%20upon%20subscribing%20to%20a%20retained%20message%20topic%20have%20the%20RETAIN%20flag%20set.%20Retained%20messages%20that%20are%20received%20by%20a%20subscribing%20client%20after%20subscription%2C%20don%27t.

Retained messages received upon subscribing to a retained message topic have the RETAIN flag set. Retained messages that are received by a subscribing client after subscription, don't.

[github-actions[bot]]

Hello! Reopening this discussion to make it searchable.