Generate building operations sample events

The schema-aware Eventstream tutorials use a building operations scenario with thermostat, occupancy, air-quality, and badge-reader events. Each event contains a deviceType field and a payload shape specific to that device type. Some events also contain nested objects.

This article shows you how to create a small Node.js application that sends the sample events to a custom endpoint source in an Eventstream.

Important

Schema-aware Eventstreams are in Preview.

Note

This generator is a documentation sample. Don't use it for production workloads or performance testing.

Prerequisites

Create the generator

  1. Create a folder named building-operations-generator.

  2. Open a terminal in the folder and run these commands:

    npm init -y
npm install @azure/event-hubs

  3. Create a file named send-building-operations-events.js.

  4. Copy the following code into the file:

    const { EventHubProducerClient } = require("@azure/event-hubs");
const { randomUUID } = require("crypto");

const connectionString =
  process.env.EVENTSTREAM_CONNECTION_STRING;
const eventHubName =
  process.env.EVENTSTREAM_EVENT_HUB_NAME;
const eventsPerType = Number(
  process.env.EVENTS_PER_TYPE || 24
);

if (!connectionString || !eventHubName) {
  throw new Error(
    "Set EVENTSTREAM_CONNECTION_STRING and " +
    "EVENTSTREAM_EVENT_HUB_NAME before running the generator."
  );
}

if (!Number.isInteger(eventsPerType) || eventsPerType < 1) {
  throw new Error("EVENTS_PER_TYPE must be a positive integer.");
}

const deviceTypes = [
  "thermostat",
  "occupancy_sensor",
  "air_quality_monitor",
  "access_badge_reader",
];

function commonFields(deviceType, index) {
  return {
    eventId: randomUUID(),
    deviceId: `${deviceType.slice(0, 4).toUpperCase()}-${String(index).padStart(3, "0")}`,
    deviceType,
    timestamp: new Date().toISOString(),
    buildingId: "BLDG-SEA-01",
  };
}

function thermostatEvent(index) {
  return {
    ...commonFields("thermostat", index),
    temperatureCelsius: 19 + Math.random() * 7,
    targetTemperatureCelsius: 22,
    hvacMode: index % 2 === 0 ? "heating" : "idle",
    location: {
      floor: (index % 4) + 1,
      room: `Room ${100 + index}`,
    },
  };
}

function occupancyEvent(index) {
  const peopleCount = index % 13;
  return {
    ...commonFields("occupancy_sensor", index),
    occupied: peopleCount > 0,
    peopleCount,
    confidencePercent: 90 + (index % 10),
    zone: {
      floor: (index % 4) + 1,
      room: `Conference Room ${String.fromCharCode(65 + (index % 4))}`,
      capacity: 12,
    },
  };
}

function airQualityEvent(index) {
  return {
    ...commonFields("air_quality_monitor", index),
    co2Ppm: 450 + (index % 12) * 35,
    pm25UgM3: 4 + (index % 8) * 0.75,
    airQualityIndex: 25 + (index % 20),
    pollutants: {
      vocPpb: 80 + (index % 10) * 5,
      carbonMonoxidePpm: 0.2 + (index % 4) * 0.1,
    },
  };
}

function badgeReaderEvent(index) {
  return {
    ...commonFields("access_badge_reader", index),
    badgeId: `BADGE-${String(1000 + index)}`,
    accessResult: index % 8 === 0 ? "denied" : "granted",
    doorName: `Floor ${(index % 4) + 1} East Entrance`,
    person: {
      employeeId: `EMP-${String(5000 + index)}`,
      department: ["Engineering", "Facilities", "Finance", "Sales"][index % 4],
    },
  };
}

const factories = {
  thermostat: thermostatEvent,
  occupancy_sensor: occupancyEvent,
  air_quality_monitor: airQualityEvent,
  access_badge_reader: badgeReaderEvent,
};

function createEvents() {
  const events = [];
  for (let index = 1; index <= eventsPerType; index += 1) {
    for (const deviceType of deviceTypes) {
      events.push(factories[deviceType](index));
    }
  }
  return events.sort(() => Math.random() - 0.5);
}

async function main() {
  const producer = new EventHubProducerClient(
    connectionString,
    eventHubName
  );

  try {
    const events = createEvents();
    let batch = await producer.createBatch();

    for (const event of events) {
      if (!batch.tryAdd({ body: event })) {
        await producer.sendBatch(batch);
        batch = await producer.createBatch();

        if (!batch.tryAdd({ body: event })) {
          throw new Error("An event is too large for an empty batch.");
        }
      }
    }

    if (batch.count > 0) {
      await producer.sendBatch(batch);
    }

    console.log(
      `Sent ${events.length} events: ` +
      `${eventsPerType} events for each device type.`
    );
  } finally {
    await producer.close();
  }
}

main().catch((error) => {
  console.error(error);
  process.exitCode = 1;
});

Configure and run the generator

  1. In PowerShell, set the custom endpoint connection details as environment variables. Replace the placeholder values with the values from your Eventstream.

    $env:EVENTSTREAM_CONNECTION_STRING = "<connection-string-primary-key>"
$env:EVENTSTREAM_EVENT_HUB_NAME = "<event-hub-name>"

  2. Optional: Change the number of events generated for each device type. The default is 24 events per type, or 96 events total.

    $env:EVENTS_PER_TYPE = "24"

  3. Run the generator:

    node .\send-building-operations-events.js

    The terminal displays a message similar to this output:

    Sent 96 events: 24 events for each device type.

  4. Return to the Eventstream and refresh Data preview. Verify that the preview contains the following deviceType values:

    • thermostat
    • occupancy_sensor
    • air_quality_monitor
    • access_badge_reader

Protect the connection credentials

The custom endpoint connection string contains a credential. Don't add the connection string to the JavaScript file, source control, screenshots, or terminal output that you share. Close the terminal or remove the environment variables when you finish the tutorial.

Remove-Item Env:\EVENTSTREAM_CONNECTION_STRING
Remove-Item Env:\EVENTSTREAM_EVENT_HUB_NAME

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