V2: Use Thing name in MQTT topic for triggering Lambda

Question

I want to be able to send messages to specific Things and have them trigger a Lambda on the Thing. I can get it working for a single Thing by hardcoding the Thing name in the YAML when I create the component:  
  
```  
lambdaFunction:  
  ...  
  componentLambdaParameters:  
    eventSources:  
      - topic: print-job/MyThing  
        type: IOT_CORE  
```  
  
But I haven't been able to find a way to make the topic dynamic. I thought `print-job/${AWS_IOT_THING_NAME}` was working when I first tried it, but I think I just misunderstood how components' configurations are updated and it wasn't actually applied because I didn't have `reset: \[""]` in the deployment. I also tried `print-job/{system:thingName}` without any luck.  
  
Is this possible to do this without using wildcards or creating a separate deployment for each Thing? And feel free to tell me if what I'm trying to do doesn't actually make sense.  
  
I'd rather not use a wildcard in the topic because each Thing only needs to receive the messages sent to the topic for that Thing. It could just discard the other messages, but that seems like a waste of resources.  
  
If there's no way to do this using LambdaManager, I can use a pinned Lambda and have it subscribe to the topic. I just wanted to check to see if there's an easier/cleaner way first.

Answer

Kinda trying the same here: https://forums.aws.amazon.com/thread.jspa?threadID=336516&tstart=0  
  
I don't think there is a way unless your lambda is pinned and "manually" subscribes to its corresponding IoT Core topic

Answer

Hi knad,  
  
Thank you for posting your question.  
Unfortunately there isn't an easier way to use a dynamic topic as you described.  
You could try either of the following:  
1. Use a wildcard in the topic.  
2. Use a pinned lambda and subscribe to it's corresponding topic.  
3. You could also explore creating a custom component https://docs.aws.amazon.com/greengrass/v2/developerguide/create-components.html instead of a lambda. You could then leverage the environment variables available to the component https://docs.aws.amazon.com/greengrass/v2/developerguide/component-environment-variables.html   
  
Please let me know if either of these options work for you.  
  
Thanks,  
Navya.

V2: Use Thing name in MQTT topic for triggering Lambda

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