Issue while using local IPC for messaging between two local component

Question

publish("test/test",message={"a":1})  
  
 def publish(self, topic, message, message_format="json"):  
        """Publishes message to a topic of AWS IOT   
  
        Args:  
            topic (string): AWS IoT Core Topic  
            message (dict / string): Message to be published  
            message_format  
        """  
  
        request = PublishToTopicRequest()  
        request.topic_name = topic  
        publish_message = PublishMessage()  
        if message_format != "json":  
            publish_message.binary_message = BinaryMessage(message=bytes(message, "utf-8"))  
            # publish_message.binary_message.message = bytes(message, "utf-8")  
        else:  
            publish_message.json_message = JsonMessage(message=message)  
            # publish_message.json_message.message = message  
  
        request.publish_message = publish_message  
        operation = self.ipc_client.new_publish_to_topic()  
        operation.activate(request)  
        future = operation.get_response()  
        future.result(TIMEOUT)

**accessControl permissions are:**  
          com.test.test:pubsub:1:  
          policyDescription: "Allows communication with other components"  
          operations:  
          - "aws.greengrass#PublishToTopic"  
          resources:  
          - "test/test"

**and Greengrass.log are:**

2021-01-06T10:30:13.515Z \[INFO] (Thread-6) software.amazon.awssdk.eventstreamrpc.RpcServer: New connection code \[AWS_ERROR_SUCCESS] for \[Id 816, Class ServerConnection, Refs 1](2021-01-06T10:30:13.515Z) - . {}  
2021-01-06T10:30:13.515Z \[INFO] (Thread-6) software.amazon.awssdk.eventstreamrpc.ServiceOperationMappingContinuationHandler: aws.greengrass#GreengrassCoreIPC authenticated identity: com.test.test. {}  
2021-01-06T10:30:13.515Z \[INFO] (Thread-6) software.amazon.awssdk.eventstreamrpc.ServiceOperationMappingContinuationHandler: Connection accepted for com.test.test. {}  
2021-01-06T10:30:13.515Z \[INFO] (Thread-6) software.amazon.awssdk.eventstreamrpc.ServiceOperationMappingContinuationHandler: Sending connect response for com.test.test. {}  
2021-01-06T10:30:13.517Z \[INFO] (Thread-6) software.amazon.awssdk.eventstreamrpc.RpcServer: New connection code \[AWS_ERROR_SUCCESS] for \[Id 818, Class ServerConnection, Refs 1](2021-01-06T10:30:13.517Z) - . {}  
2021-01-06T10:30:13.517Z \[INFO] (Thread-6) software.amazon.awssdk.eventstreamrpc.ServiceOperationMappingContinuationHandler: aws.greengrass#GreengrassCoreIPC authenticated identity: com.test.test {}  
2021-01-06T10:30:13.517Z \[INFO] (Thread-6) software.amazon.awssdk.eventstreamrpc.ServiceOperationMappingContinuationHandler: Connection accepted for com.test.test. {}  
2021-01-06T10:30:13.517Z \[INFO] (Thread-6) software.amazon.awssdk.eventstreamrpc.ServiceOperationMappingContinuationHandler: Sending connect response for com.test.test. {}  
2021-01-06T10:30:13.518Z \[ERROR] (Thread-6) com.aws.greengrass.ipc.common.ExceptionUtil: Unhandled exception in IPC. {}  
java.lang.NullPointerException  
  
Edited by: allenkallz on Jan 6, 2021 3:21 AM

MichaelDombrowski-AWS · Answer

Hi and thanks for using Greengrass v2.  
  
Is there any additional logging after the NullPointerException? There ought to be a stacktrace which would tells us exactly what the problem is.  
  
Thanks!  
  
Michael Dombrowski.

rePost-User-1768441 · Answer

Hi   
Thanks for your reply.  
  
The issue is in AWS IoT Python SDK v2 that for communication with the local component we have to create request instance **PublishToTopicRequest**  that accept topic with-param name "topic"  
  
but when we have to communicate with Cloud then we have to create request instance **PublishToIoTTopicRequest** and this class accepts topic with-param name   **topic_name**.    I have one question why you don`t have the same param name at both places. It`s confusing  
  
See the param names of both classes in the attachment.  
 And previously it`s not mentioned in Greengrass v2 documentation.  
  
Edited by: allenkallz on Jan 8, 2021 8:37 AM

MichaelDombrowski-AWS · Answer

Based on that stacktrace, that must mean that the topic is null. Please ensure that you have set a non-null topic name in the publish request.  
  
request.topic = "my/topic/name"  
  
Thanks.  
Michael Dombrowski  
  
Edited by: MichaelDombrowski-AWS on Jan 7, 2021 9:08 AM

Issue while using local IPC for messaging between two local component

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