AWS IoT Demo

This project is a quick demo for using AWS IoT to collect CPU temperature from an edge device, and record it in DynamoDB every 10 seconds. There will be a RESTful API to query the data.

This demo will cover the following parts:

• The Edge Device
• AWS Lambda (storing and querying data against DynamoDB)
• DynamoDB
• API Gateway
• MQTT

The Edge Device

It can be any device that compatible with AWS IoT. In this example, I am using my home Plex Media Server (running Ubuntu Server) as the edge device.

Collecting CPU Temperature Data

Collecting CPU temperature data is done via Node-RED. A node module node-red-contrib-cpu is used to read CPU temperature from local sensors.

Collected data is published to AWS IoT via MQTT

The flow script can be found in node-red/flow.json, which can be imported into Node-RED. You need to replace with your own AWS certificates and endpoints

Data published into MQTT are in following format:

{
  "topic": "temperature/cpu",
  "payload": {
    "deviceId": "mediaserver_0",
    "temperature": 42
  },
  "_msgid": "523478a5.762668"
}

AWS Lambda

cpuTemperatureStore

Script file src/cpuTempertureStore/index.js.

This lambda will be triggered when a MQTT message is published by edge device, and the data will be stored into DynamoDB.

cpuTemperatureQuery

Script file src/cpuTempertureQuery/index.js.

This lambda handles RESTful query API to query data from DynamoDB. Depending on how your Gateway API is configured, the base URL will be different. Assuming the URL is `https://someid.execute-api.your-region.amazonaws.com/prod/demo, below are query examples:

1. Query last 60 second temperatures (default)

curl https://someid.execute-api.your-region.amazonaws.com/prod/demo

2. Query last 120 second temperatures

curl https://someid.execute-api.your-region.amazonaws.com/prod/demo?du=120

3. Query specified period

curl https://someid.execute-api.your-region.amazonaws.com/prod/demo?du=120&start=2020-11-01T10:30:33Z

DynamoDB

Table

Table name here is cpu_temperature, partition key id with a sort key receivedAt.

API Gateway

An API need to be created under API Gateway and link to cpuTemperatureQuery lambda.

MQTT

In AWS IoT Core, a thing need be created in order to generate certificates, where can be imported into Node-RED as used in edge device.

Then a rule need be created to subscribe a topic from MQTT and trigger the cpuTemperatureStore lambda.

Other Requirements

AWS IAM knowledge are essential to create roles and assign permissions, in order to make all these parts work together.