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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

Flow

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
  1. Query last 120 second temperatures
curl https://someid.execute-api.your-region.amazonaws.com/prod/demo?du=120
  1. 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.

Table

API Gateway

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

API

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.

rule

Other Requirements

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