occasionally getting 2 shadow read callbacks back to back when expected only 1

[psddas]

Describe the bug

I am occasionally getting 2 shadow read callbacks back to back when expected only 1.

this is causing a crash in my code based on the internal logic.

--
code:

m_shadowClient->SubscribeToGetNamedShadowAccepted(
    namedShadowSubscriptionRequest,
    AWS_MQTT_QOS_AT_LEAST_ONCE,
    onGetShadowAcceptedNamed,
    onGetShadowUpdatedAcceptedSubAck);

2025-05-12 11:15:46: IOT-SHDW: I: 3481: 10844: read_update :: Classic Shadow : {"state":{"desired":{"...

2025-05-12 11:16:16: IOT-SHDW: I: 3481: 10844: read_update :: Classic Shadow : {"state":{"desired":{"...

Signal 0x6 received from thread 10844
Linux signal, Service: IOT, PID: 3481, TID: 10844, signum: 6

Expected Behavior

Only 1 callback for the read shadow

Current Behavior

sometime I am seeing 2 callbacks for the resd-shadow after connection is done

Reproduction Steps

random

Possible Solution

No response

Additional Information/Context

No response

SDK version used

v1.27.0

Environment details (OS name and version, etc.)

Linux

[bretambrose]

There is no guarantee that a QoS1 message will only be delivered once by the broker. Your application must be able to handle duplicates.

[pranoyd-nd]

When I used AWS_MQTT_QOS_EXACTLY_ONCE, the connection is interrupted with error "unexpected hungup" and resuming back-to-back.

Will it gurantee one callback? Any known issue with AWS_MQTT_QOS_EXACTLY_ONCE?

[bretambrose]

IoT Core does not support QoS 2.

Consider tracking and using the version field to determine whether or not you should use a response.

[pranoyd-nd]

@bretambrose , thank you !