Greengrass V2 Pub/Sub Hello World

Question

I am doing the "com.example.HelloWorld" tutorial on Python Greengrass V2. I added the tutorial stuff and am using ipc_client.new_publish_to_iot_core() to push a message to the core (per all the online example code) - and added the permissions stuff for it in my deployment. I am doing LOCAL development of this function - using greengrass-cli to create and restart it - and looking at the logs (and timestamps) to confirm it's running.  
  
It APPEARS to be working in that it is nothing is throwing errors - and the prints I have before and after the publish all are coming out.  
  
But my question is - I thought if I went to the "test->MQTT Test client" in the IoT GUI, and subscribed to the "#" topic - I should be able to see my messages get published - but I am not. I saw another demo online in which this is exactly what they did.  
  
So - is this the correct way to see if stuff is getting published? Or is there somethiing else. And if so - and idea why this wouldn't be working??

Accepted Answer

I can see that you are using the ipc_client.new_publish_to_topic() method. This is used for local pub/sub as shown here . Instead you should be using ipc_client.new_publish_to_iot_core() as shown in the publish to IoT core tutorial (and also add relevant permissions) as shown here

Answer

Hi Bradley,   
1. Can you check the IAM Role (associated to the IoT Role alias) for the GG Core to make sure it has permissions to publish to the IoT Core? Can you share the policy document?  
2. To debug further, it will be helpful to get the debug logs for both the component and greengrass.log. Have you taken a look at the greengrass.log file for any clues?  
  
Thanks

Answer

Thanks for the help! I assume from your response I SHOULD be seeing the published message in the console??  
  
My log output is:  
  
2021-11-14T01:20:32.376Z \[INFO] (pool-2-thread-36) com.example.HelloWorld: shell-runner-start. {scriptName=services.com.example.HelloWorld.lifecycle.Run, serviceName=com.example.HelloWorld, currentState=STARTING, command=\["python3 -u /greengrass/v2/packages/artifacts/com.example.HelloWorld/1.0.0/hell..."]}  
2021-11-14T01:20:32.716Z \[INFO] (Copier) com.example.HelloWorld: stdout. BKG2 Hello, world! Current time: 2021-11-14 01:20:32.715702.. {scriptName=services.com.example.HelloWorld.lifecycle.Run, serviceName=com.example.HelloWorld, currentState=RUNNING}  
2021-11-14T01:20:32.727Z \[INFO] (Copier) com.example.HelloWorld: stdout. SCRIPT DONE. {scriptName=services.com.example.HelloWorld.lifecycle.Run, serviceName=com.example.HelloWorld, currentState=RUNNING}  
2021-11-14T01:20:32.773Z \[INFO] (Copier) com.example.HelloWorld: Run script exited. {exitCode=0, serviceName=com.example.HelloWorld, currentState=RUNNING}  
  
i.e. There is NOT reference to the publish failing.  
  
MQTT Test Client is showing a few events like:  
$aws/events/subscriptions...  
and  
$aws/events/presence/...  
  
for my GG node if I restart the Nucleus - so something is connecting. But nothing for the topic I am publishing to or anything else on the "#" topic.  
  
The script (I removed a little to make it shorter):  
  
message = "BKG2 Hello, %s! Current time: %s." % (sys.argv\[1], datetime.datetime.now())  
print(message)  
ipc_client = awsiot.greengrasscoreipc.connect()  
topic = "my/topic"  
message = "Hello, World!"  
request = PublishToTopicRequest()  
request.topic = topic  
publish_message = PublishMessage()  
publish_message.binary_message = BinaryMessage()  
publish_message.binary_message.message = bytes(message, "utf-8")  
request.publish_message = publish_message  
operation = ipc_client.new_publish_to_topic()  
operation.activate(request)  
future = operation.get_response()  
future.result(10)  
print ("SCRIPT DONE")  
  
IAM access advisor says that any IoT accesses were "Not accessed in the tracking period"  
  
The IAM policy for this thing is as follows:  
  
{  
    "Version": "2012-10-17",  
    "Statement": \[  
        {  
            "Sid": "VisualEditor0",  
            "Effect": "Allow",  
            "Action": \[  
                "logs:ListTagsLogGroup",  
                "iot:ListProvisioningTemplateVersions",  
                "logs:DeleteSubscriptionFilter",  
                "logs:DescribeLogStreams",  
                "iot:ListJobExecutionsForJob",  
                "logs:DescribeSubscriptionFilters",  
                "logs:StartQuery",  
                "logs:DescribeMetricFilters",  
                "iot:ListThingsInThingGroup",  
                "iot:ListTargetsForSecurityProfile",  
                "logs:DeleteLogStream",  
                "iot:ListJobExecutionsForThing",  
                "iot:ListSecurityProfilesForTarget",  
                "logs:CreateExportTask",  
                "logs:CreateLogStream",  
                "logs:DeleteMetricFilter",  
                "iot:Subscribe",  
                "iot:GetBehaviorModelTrainingSummaries",  
                "iot:ListDetectMitigationActionsExecutions",  
                "logs:DeleteRetentionPolicy",  
                "logs:GetLogEvents",  
                "iot:ListPolicyVersions",  
                "iot:GetThingShadow",  
                "logs:AssociateKmsKey",  
                "logs:FilterLogEvents",  
                "iot:Publish",  
                "iot:ListViolationEvents",  
                "logs:DisassociateKmsKey",  
                "iot:ListNamedShadowsForThing",  
                "logs:DescribeLogGroups",  
                "logs:DeleteLogGroup",  
                "iot:ListSecurityProfiles",  
                "logs:CreateLogGroup",  
                "logs:PutLogEvents",  
                "iot:UpdateThingShadow",  
                "logs:PutMetricFilter",  
                "iot:Receive",  
                "iot:ListActiveViolations",  
                "iot:ListTargetsForPolicy",  
                "iot:ListThingsInBillingGroup",  
                "iot:ListThingGroupsForThing",  
                "logs:PutSubscriptionFilter",  
                "logs:PutRetentionPolicy",  
                "logs:GetLogGroupFields"  
            ],  
            "Resource": \[  
                "arn:aws:logs:us-east-1:583841319539:log-group:greengrasstest:log-stream:*",  
                "arn:aws:logs:us-east-1:583841319539:log-group:greengrasstest",  
                "arn:aws:iot:**:583841319539:thinggroup/**"  
            ]  
        },  
        {  
            "Sid": "VisualEditor1",  
            "Effect": "Allow",  
            "Action": \[  
                "logs:ListTagsLogGroup",  
                "iot:ListProvisioningTemplateVersions",  
                "logs:DeleteSubscriptionFilter",  
                "logs:DescribeLogStreams",  
                "iot:ListJobExecutionsForJob",  
                "logs:DescribeSubscriptionFilters",  
                "logs:StartQuery",  
                "logs:DescribeMetricFilters",  
                "iot:ListTargetsForSecurityProfile",  
                "logs:DeleteLogStream",  
                "iot:ListJobExecutionsForThing",  
                "logs:CreateExportTask",  
                "logs:CreateLogStream",  
                "logs:DeleteMetricFilter",  
                "iot:Subscribe",  
                "iot:GetBehaviorModelTrainingSummaries",  
                "iot:ListDetectMitigationActionsExecutions",  
                "logs:DeleteRetentionPolicy",  
                "logs:GetLogEvents",  
                "iot:ListPolicyVersions",  
                "iot:GetThingShadow",  
                "logs:AssociateKmsKey",  
                "logs:FilterLogEvents",  
                "iot:Publish",  
                "iot:ListViolationEvents",  
                "logs:DisassociateKmsKey",  
                "iot:ListNamedShadowsForThing",  
                "logs:DescribeLogGroups",  
                "logs:DeleteLogGroup",  
                "iot:ListSecurityProfiles",  
                "logs:CreateLogGroup",  
                "logs:PutLogEvents",  
                "iot:UpdateThingShadow",  
                "logs:PutMetricFilter",  
                "iot:Receive",  
                "iot:ListActiveViolations",  
                "iot:ListTargetsForPolicy",  
                "iot:ListThingsInBillingGroup",  
                "iot:ListThingGroupsForThing",  
                "logs:PutSubscriptionFilter",  
                "logs:PutRetentionPolicy",  
                "logs:GetLogGroupFields"  
            ],  
            "Resource": \[  
                "arn:aws:logs:us-east-1:583841319539:log-group:greegrasstest:log-stream:*",  
                "arn:aws:logs:us-east-1:583841319539:log-group:greengrasstest",  
                "arn:aws:iot:**:583841319539:custommetric/**",  
                "arn:aws:iot:**:583841319539:dimension/**",  
                "arn:aws:iot:**:583841319539:topic/**",  
                "arn:aws:iot:**:583841319539:thing/**",  
                "arn:aws:iot:**:583841319539:securityprofile/**",  
                "arn:aws:iot:**:583841319539:topicfilter/**",  
                "arn:aws:iot:**:583841319539:job/**",  
                "arn:aws:iot:**:583841319539:provisioningtemplate/**",  
                "arn:aws:iot:**:583841319539:billinggroup/**",  
                "arn:aws:iot:**:583841319539:policy/**"  
            ]  
        },  
        {  
            "Sid": "VisualEditor2",  
            "Effect": "Allow",  
            "Action": \[  
                "logs:ListTagsLogGroup",  
                "logs:DisassociateKmsKey",  
                "logs:DeleteSubscriptionFilter",  
                "logs:DescribeLogGroups",  
                "logs:DeleteLogGroup",  
                "logs:DescribeLogStreams",  
                "logs:DescribeSubscriptionFilters",  
                "logs:StartQuery",  
                "logs:DescribeMetricFilters",  
                "logs:CreateLogGroup",  
                "logs:DeleteLogStream",  
                "logs:PutLogEvents",  
                "logs:CreateExportTask",  
                "logs:PutMetricFilter",  
                "logs:CreateLogStream",  
                "logs:DeleteMetricFilter",  
                "logs:DeleteRetentionPolicy",  
                "logs:GetLogEvents",  
                "logs:AssociateKmsKey",  
                "logs:FilterLogEvents",  
                "logs:PutSubscriptionFilter",  
                "logs:PutRetentionPolicy",  
                "logs:GetLogGroupFields"  
            ],  
            "Resource": "arn:aws:logs:us-east-1:583841319539:log-group:greegrasstest"  
        },  
        {  
            "Sid": "VisualEditor3",  
            "Effect": "Allow",  
            "Action": \[  
                "iot:ListOTAUpdates",  
                "logs:GetLogRecord",  
                "iot:ListAuditSuppressions",  
                "iot:ListTunnels",  
                "iot:ListV2LoggingLevels",  
                "iot:ListAuditMitigationActionsExecutions",  
                "iot:ListBillingGroups",  
                "logs:ListLogDeliveries",  
                "iot:ListJobTemplates",  
                "iot:Subscribe",  
                "iot:ListScheduledAudits",  
                "logs:CancelExportTask",  
                "iot:ListDomainConfigurations",  
                "iot:ListThingRegistrationTasks",  
                "iot:ListMitigationActions",  
                "iot:ListDetectMitigationActionsTasks",  
                "logs:DescribeDestinations",  
                "iot:ListCertificatesByCA",  
                "iot:ListAuditFindings",  
                "logs:StopQuery",  
                "logs:DeleteQueryDefinition",  
                "iot:ListCustomMetrics",  
                "iot:Receive",  
                "logs:CreateLogDelivery",  
                "logs:DescribeExportTasks",  
                "iot:ListAuditMitigationActionsTasks",  
                "iot:ListPrincipalThings",  
                "logs:GetQueryResults",  
                "logs:UpdateLogDelivery",  
                "iot:ListPolicies",  
                "iot:ListFleetMetrics",  
                "iot:ListRoleAliases",  
                "iot:ListIndices",  
                "iot:ListThings",  
                "iot:ListTopicRuleDestinations",  
                "iot:ListDimensions",  
                "iot:ListOutgoingCertificates",  
                "iot:ListCACertificates",  
                "logs:GetLogDelivery",  
                "iot:ListThingGroups",  
                "iot:ListPrincipalPolicies",  
                "logs:DeleteLogDelivery",  
                "iot:ListProvisioningTemplates",  
                "logs:DescribeQueryDefinitions",  
                "logs:PutDestination",  
                "logs:DescribeResourcePolicies",  
                "iot:Publish",  
                "iot:ListThingRegistrationTaskReports",  
                "logs:DescribeQueries",  
                "iot:ListAuditTasks",  
                "iot:ListTopicRules",  
                "logs:PutDestinationPolicy",  
                "iot:ListPolicyPrincipals",  
                "logs:TestMetricFilter",  
                "logs:DeleteDestination",  
                "logs:PutQueryDefinition",  
                "iot:ListAttachedPolicies",  
                "iot:ListThingTypes",  
                "iot:ListRetainedMessages",  
                "iot:ListStreams",  
                "iot:ListThingPrincipals",  
                "iot:ListAuthorizers",  
                "iot:ListJobs",  
                "iot:UpdateThing",  
                "iot:ListCertificates"  
            ],  
            "Resource": "*"  
        }  
    ]  
}

Greengrass V2 Pub/Sub Hello World

Relevant content