Getting started with Greengrass connectors (CLI)

First, create the secret.

aws secretsmanager create-secret --name greengrass-TwilioAuthToken --secret-string twilio-auth-token

Copy the ARN of the secret from the output. You use this to create the secret resource and to configure the Twilio Notifications connector.

Create a resource definition that includes an initial version.

Copy the LatestVersionArn of the resource definition from the output. You use this value to add the resource definition version to the group version that you deploy to the core.

Create a connector definition with an initial version.

Copy the LatestVersionArn of the connector definition from the output. You use this value to add the connector definition version to the group version that you deploy to the core.

From the AWS IoT Greengrass Core SDK downloads page, download the AWS IoT Greengrass Core SDK for Python to your computer.

Unzip the downloaded package to get the SDK. The SDK is the greengrasssdk folder.

Save the following Python code function in a local file named temp_monitor.py.

import greengrasssdk
import json
import random

client = greengrasssdk.client('iot-data')

# publish to the Twilio Notifications connector through the twilio/txt topic
def function_handler(event, context):
    temp = event['temperature']
    
    # check the temperature
    # if greater than 30C, send a notification
    if temp > 30:
        data = build_request(event)
        client.publish(topic='twilio/txt', payload=json.dumps(data))
        print('published:' + str(data))
        
    print('temperature:' + str(temp))
    return

# build the Twilio request from the input data
def build_request(event):
    to_name = event['to_name']
    to_number = event['to_number']
    temp_report = 'temperature:' + str(event['temperature'])

    return {
        "request": {
            "recipient": {
                "name": to_name,
                "phone_number": to_number,
                "message": temp_report
            }
        },
        "id": "request_" + str(random.randint(1,101))
    }

Zip the following items into a file named temp_monitor_python.zip. When creating the ZIP file, include only the code and dependencies, not the containing folder.

This is your Lambda function deployment package.

Create an IAM role so you can pass in the role ARN when you create the function.

Copy the Arn from the output.

Use the AWS Lambda API to create the TempMonitor function. The following command assumes that the zip file is in the current directory.

aws lambda create-function \
--function-name TempMonitor \
--zip-file fileb://temp_monitor_python.zip \
--role role-arn \
--handler temp_monitor.function_handler \
--runtime python3.7

Publish a version of the function.

aws lambda publish-version --function-name TempMonitor --description 'First version'

Create an alias for the published version.

Greengrass groups can reference a Lambda function by alias (recommended) or by version. Using an alias makes it easier to manage code updates because you don't have to change your subscription table or group definition when the function code is updated. Instead, you just point the alias to the new function version.

aws lambda create-alias --function-name TempMonitor --name GG_TempMonitor --function-version 1

Copy the AliasArn from the output. You use this value when you configure the function for AWS IoT Greengrass and when you create a subscription.

Create a function definition that includes an initial version.

Copy the LatestVersionArn from the output. You use this value to add the function definition version to the group version that you deploy to the core.

Copy the Id from the output. You use this value later when you update the function.

Create a subscription definition that contains an initial version that includes the subscriptions.

Copy the LatestVersionArn from the output. You use this value to add the subscription definition version to the group version that you deploy to the core.

Get the ID of the group and latest group version:

1. Get the IDs of the target Greengrass group and group version. This procedure assumes that this is the latest group and group version. The following query returns the most recently created group.

   aws greengrass list-groups --query "reverse(sort_by(Groups, &CreationTimestamp))[0]"

   Or, you can query by name. Group names are not required to be unique, so multiple groups might be returned.

   aws greengrass list-groups --query "Groups[?Name=='MyGroup']"

   Note

   You can also find these values in the AWS IoT console. The group ID is displayed on the group's Settings page. Group version IDs are displayed on the group's Deployments tab.

2. Copy the Id of the target group from the output. You use this to get the core definition version and when you deploy the group.

3. Copy the LatestVersion from the output, which is the ID of the last version added to the group. You use this to get the core definition version.

Get the ARN of the core definition version:

1. Get the group version. For this step, we assume that the latest group version includes a core definition version.

   • Replace group-id with the Id that you copied for the group.

   • Replace group-version-id with the LatestVersion that you copied for the group.

   aws greengrass get-group-version \
   --group-id group-id \
   --group-version-id group-version-id

2. Copy the CoreDefinitionVersionArn from the output.

Create a group version.

aws greengrass create-group-version \
--group-id group-id \
--core-definition-version-arn core-definition-version-arn \
--resource-definition-version-arn resource-definition-version-arn \
--connector-definition-version-arn connector-definition-version-arn \
--function-definition-version-arn function-definition-version-arn \
--subscription-definition-version-arn subscription-definition-version-arn

Copy the value of Version from the output. This is the ID of the group version. You use this value to deploy the group version.

In a core device terminal, make sure that the AWS IoT Greengrass daemon is running.

1. To check whether the daemon is running:

   ps aux | grep -E 'greengrass.*daemon'

   If the output contains a root entry for /greengrass/ggc/packages/1.11.6/bin/daemon, then the daemon is running.

2. To start the daemon:

   cd /greengrass/ggc/core/
   sudo ./greengrassd start

Create a deployment.

aws greengrass create-deployment \
--deployment-type NewDeployment \
--group-id group-id \
--group-version-id group-version-id

Copy the DeploymentId from the output.

Get the deployment status.

aws greengrass get-deployment-status \
--group-id group-id \
--deployment-id deployment-id

If the status is Success, the deployment was successful. For troubleshooting help, see Troubleshooting AWS IoT Greengrass.

On the AWS IoT console home page, choose Test.

For Subscribe to topic, use the following values, and then choose Subscribe. The Twilio Notifications connector publishes status information to this topic.

For Publish to topic, use the following values, and then choose Publish to invoke the function.

{
   "to_name": "recipient-name",
   "to_number": "recipient-phone-number",
   "temperature": 31
}

If successful, the recipient receives the text message and the console displays the success status from the output data.

Now, change the temperature in the input message to 29 and publish. Because this is less than 30, the TempMonitor function doesn't trigger a Twilio message.