1st published message does not get received by subscribe callback

[cbumgard]

Hi there, when I run the subscribe_publish_sample with a single publish, the subscribe callback never runs. The subscribe callback gets invoked x - 1 times, where x is set via the command-line and is represented as publishCount in the code. However the CloudWatch log shows the correct number of x published messages, so it appears to just not be sending back from the broker to the local client for the first published message.

As I'm adapting this sample for my own use, and would like to understand if this is a bug or expected behavior.

Here is example output:

x=1 does not show the subscribe callback:

$ ./subscribe_publish_sample -x 1
...
Subscribing...
-->sleep
Publish done

Shows (x - 1) messages in subscribe callback:

$ ./subscribe_publish_sample -x 3
...
Subscribing...
-->sleep
Subscribe callback
sdkTest/sub	hello from SDK QOS1 : 1 
Subscribe callback
sdkTest/sub	hello from SDK QOS0 : 0 
-->sleep
Publish done

[chaurah]

Hi @cbumgard,
Its a bug in the sample. The loop that is doing publish exits here without waiting for the last set of messages to be received. I have made a note of this and will improve the sample for the next release. Until then, you should be able to resolve it by simply adding an aws_iot_mqtt_yield after the loop ends to catch any messages that have not been received yet.

Thank you for pointing this out. Please let us know if you have further questions.

Rahul

[cbumgard]

Understood, thank you @chaurah