Telemetry Data Generator

This is a simple telemetry generator that can be used to generate telemetry data for testing purposes. It was built for the Azure Data Explorer Microhack as a replacement for the IoT Central dependency.

Read the Blog

This repository accompanies my blog post on Medium titled Build your own Telemetry Data Generator to Simulate IoT and OT Devices which it walks you through customising this generator to suit the unique shape of your data - this way you can mimic your real-world data in a test environment.

Deploy to Azure

To deploy this generator to Azure, click the button below. You will need an Azure Subscription and permission to create the resources shown in the image.

How it works

The generator simulates telemetry from 30 devices whose ids are defined in the src/deviceIds.ts file. We want the generator to emit payloads for the same simulated devices each time, thus we hardcode the device ids to keep them consistent between runs.

Every 1 minute, the src/functions/TelemetryGenerator.ts runs and emits a payload for each device ID. The payload is a JSON object which matches the expected format for the IoT Central API.

The payload array is then written onto the Event Hub for later ingestion into a KQL Database (or other downstream system).

How to use

To adjust the Event Hub name and connection string, edit the src/functions/TelemetryGenerator.ts file. Here you can also adjust the frequency of the payload generation.

...
// Schedule the function to run every minute and push into the iotdata Event Hub.
app.timer("TelemetryGenerator", {
  schedule: "0 */1 * * * *",
  handler: TelemetryGenerator,
  return: output.eventHub({
    eventHubName: "iotdata", // <-- Name of the Azure Event Hub
    connection: "EventHubConnection", // <-- Environment variable (connection string)
  }),
});

Be sure to supply the EventHubConnection environment variable when deploying the function app. The value is the connection string of your Azure Event Hubs Namespace.

In Development

Locally this can be supplied in a local.settings.json file like so:

{
  "IsEncrypted": false,
  "Values": {
    "AzureWebJobsStorage": "DefaultEndpointsProtocol=...",
    "FUNCTIONS_WORKER_RUNTIME": "node",
    "AzureWebJobsFeatureFlags": "EnableWorkerIndexing",
    "EventHubConnection": "Endpoint=sb://..."
  }
}

In Production

Add the EventHubConnection environment variable in the Azure Function's Configuration settings. The value should be the Azure Event Hub connection string, e.g.

Key	Value
EventHubConnection	Endpoint=sb://...