How can I publish to a MQTT topic in a Amazon AWS Lambda function?

Question

I would like to have an easy command like I use in the bash to publish something to a topic on MQTT inside a AWS Lambda function. Along the lines of: mosquitto_pub -h my.server.com -t "light/set" -m "on"

Background: I would like to turn a lamp on and off with Alexa. Alexa can start a Lambda function, and inside of this Lambda function I would like to start an MQTT publish, because the lamp can listen to a MQTT topic and react on the messages there.(Maybe there are easier solutions, but we are in a complicated (university) network which makes many other approaches more difficult)

Answer 1

If you are using Python, I was able to get an AWS Lambda function to publish a message to AWS IoT using the following inside my handler function:

import boto3
import json

client = boto3.client('iot-data', region_name='us-east-1')

# Change topic, qos and payload
response = client.publish(
        topic='$aws/things/pi/shadow/update',
        qos=1,
        payload=json.dumps({"foo":"bar"})
    )

You will also need to ensure that the Role (in your Lambda function configuration) has a policy attached to allow access to IoT publish function. Under IAM -> Roles you can add an inline policy to your Lambda function Role like:

{
   "Version": "2016-6-25",
   "Statement": [
    {
        "Effect": "Allow",
        "Action": [
            "iot:Publish"
        ],
        "Resource": [
            "*"
        ]
    }
   ]
}