Greengrass Subscribe to Topic

Question

My greengrass uses a custom component which publishes events from greengrass up to the cloud. I use the publish_binary_message_to_topic(ipc_client, , ). Works great. I now want to have my custom component subscribe to messages on the same topic. So, I tried /

Greg · Accepted Answer

Hi. `SubscribeToTopic` and `PublishToTopic` are for local communications to other components on Greengrass. To interact with AWS IoT Core, there are different IPC methods: https://docs.aws.amazon.com/greengrass/v2/developerguide/ipc-iot-core-mqtt.html

jrcarb-AWS · Answer

Hey Will,
One thing you can check is to make sure you have the proper "accessControl" policies setup for your component.

You can use this documentation section as a guide for example code and how to publish and subscribe to topics using the ipc_client.
https://docs.aws.amazon.com/greengrass/v2/developerguide/interprocess-communication.html

Will · Answer

Ok.  I got it.  Thank you.

Will · Answer

Yeah,  this is exactly the code I'm trying to get to work.  I'm using Nuc version 2.12.2. The example code is not working for me -- only for the publish.

Will · Answer

This is my access control policy in my custom component:
  "accessControl": {
    "aws.greengrass.ipc.pubsub": {
      "com.thio.coredevice.thio_bp:pubsub:1": {
        "policyDescription": "Allows access to publish/subscribe to topics.",
        "operations": [
          "aws.greengrass#SubscribeToTopic",
          "aws.greengrass#PublishToTopic"
        ],
        "resources": [
          "thio_bin_demo"
        ]
      },
      "com.thio.coredevice.thio_bp:pubsub:2": {
        "policyDescription": "Allows access to publish/subscribe to topics.",
        "operations": [
          "aws.greengrass#SubscribeToTopic",
          "aws.greengrass#PublishToTopic"
        ],
        "resources": [
          "thio_bin_demo/request"
        ]
      }
    }
  },

Greengrass Subscribe to Topic

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