Extend Azure IoT Central with custom rules using Stream Analytics, Azure Functions, and SendGrid

Članak
12/28/2021
8 min. za čitanje

This how-to guide shows you how to extend your IoT Central application with custom rules and notifications. The example shows sending a notification to an operator when a device stops sending telemetry. The solution uses an Azure Stream Analytics query to detect when a device has stopped sending telemetry. The Stream Analytics job uses Azure Functions to send notification emails using SendGrid.

This how-to guide shows you how to extend IoT Central beyond what it can already do with the built-in rules and actions.

In this how-to guide, you learn how to:

Stream telemetry from an IoT Central application using continuous data export.
Create a Stream Analytics query that detects when a device has stopped sending data.
Send an email notification using the Azure Functions and SendGrid services.

Prerequisites

To complete the steps in this how-to guide, you need an active Azure subscription.

If you don't have an Azure subscription, create a free account before you begin.

IoT Central application

Create an IoT Central application on the Azure IoT Central application manager website with the following settings:

Setting	Value
Pricing plan	Standard
Application template	In-store analytics – condition monitoring
Application name	Accept the default or choose your own name
URL	Accept the default or choose your own unique URL prefix
Directory	Your Azure Active Directory tenant
Azure subscription	Your Azure subscription
Region	Your nearest region

The examples and screenshots in this article use the United States region. Choose a location close to you and make sure you create all your resources in the same region.

This application template includes two simulated thermostat devices that send telemetry.

Resource group

Use the Azure portal to create a resource group called DetectStoppedDevices to contain the other resources you create. Create your Azure resources in the same location as your IoT Central application.

Event Hubs namespace

Use the Azure portal to create an Event Hubs namespace with the following settings:

Setting	Value
Name	Choose your namespace name
Pricing tier	Basic
Subscription	Your subscription
Resource group	DetectStoppedDevices
Location	East US
Throughput Units	1

Stream Analytics job

Use the Azure portal to create a Stream Analytics job with the following settings:

Setting	Value
Name	Choose your job name
Subscription	Your subscription
Resource group	DetectStoppedDevices
Location	East US
Hosting environment	Cloud
Streaming units	3

Function app

Use the Azure portal to create a function app with the following settings:

Setting	Value
App name	Choose your function app name
Subscription	Your subscription
Resource group	DetectStoppedDevices
OS	Windows
Hosting Plan	Consumption Plan
Location	East US
Runtime Stack	.NET
Storage	Create new

SendGrid account and API Keys

If you don't have a Sendgrid account, create a free account before you begin.

From the Sendgrid Dashboard Settings on the left menu, select API Keys.
Click Create API Key.
Name the new API key AzureFunctionAccess.
Click Create & View.

Afterwards, you will be given an API key. Save this string for later use.

Create an event hub

You can configure an IoT Central application to continuously export telemetry to an event hub. In this section, you create an event hub to receive telemetry from your IoT Central application. The event hub delivers the telemetry to your Stream Analytics job for processing.

In the Azure portal, navigate to your Event Hubs namespace and select + Event Hub.
Name your event hub centralexport, and select Create.

Your Event Hubs namespace looks like the following screenshot:


## Define the function

This solution uses an Azure Functions app to send an email notification when the Stream Analytics job detects a stopped device. To create your function app:

1. In the Azure portal, navigate to the **App Service** instance in the **DetectStoppedDevices** resource group.
1. Select **+** to create a new function.
1. Select **HTTP Trigger**.
1. Select **Add**.

    :::image type="content" source="media/howto-create-custom-rules/add-function.png" alt-text="Image of the Default HTTP trigger function"::: 

## Edit code for HTTP Trigger

The portal creates a default function called **HttpTrigger1**:

```:::image type="content" source="media/howto-create-custom-rules/default-function.png" alt-text="Screenshot of Edit HTTP trigger function.":::

1. Replace the C# code with the following code:

    ```csharp
    #r "Newtonsoft.Json"
    #r "SendGrid"
    using System;
    using SendGrid.Helpers.Mail;
    using Microsoft.Azure.WebJobs.Host;
    using Microsoft.AspNetCore.Mvc;
    using Microsoft.Extensions.Primitives;
    using Newtonsoft.Json;

    public static SendGridMessage Run(HttpRequest req, ILogger log)
    {
        string requestBody = new StreamReader(req.Body).ReadToEnd();
        log.LogInformation(requestBody);
        var notifications = JsonConvert.DeserializeObject<IList<Notification>>(requestBody);

        SendGridMessage message = new SendGridMessage();
        message.Subject = "Contoso device notification";

        var content = "The following device(s) have stopped sending telemetry:<br/><br/><table><tr><th>Device ID</th><th>Time</th></tr>";
        foreach(var notification in notifications) {
            log.LogInformation($"No message received - Device: {notification.deviceid}, Time: {notification.time}");
            content += $"<tr><td>{notification.deviceid}</td><td>{notification.time}</td></tr>";
        }
        content += "</table>";
        message.AddContent("text/html", content);  

        return message;
    }

    public class Notification
    {
        public string deviceid { get; set; }
        public string time { get; set; }
    }
    ```

    You may see an error message until you save the new code.
1. Select **Save** to save the function.

## Add SendGrid Key

To add your SendGrid API Key, you need to add it to your **Function Keys** as follows:

1. Select **Function Keys**.
1. Choose **+ New Function Key**.
1. Enter the *Name* and *Value* of the API Key you created before.
1. Click **OK.**

    :::image type="content" source="media/howto-create-custom-rules/add-key.png" alt-text="Screenshot of Add Sangrid Key.":::


## Configure HttpTrigger function to use SendGrid

To send emails with SendGrid, you need to configure the bindings for your function as follows:

1. Select **Integrate**.
1. Choose **Add Output** under **HTTP ($return)**.
1. Select **Delete.**
1. Choose **+ New Output**.
1. For Binding Type, then choose **SendGrid**.
1. For SendGrid API Key Setting Type, click New.
1. Enter the *Name* and *Value* of your SendGrid API key.
1. Add the following information:

| Setting | Value |
| ------- | ----- |
| Message parameter name | Choose your name |
| To address | Choose the name of your To Address |
| From address | Choose the name of your From Address |
| Message subject | Enter your subject header |
| Message text | Enter the message from your integration |

1. Select **OK**.

    :::image type="content" source="media/howto-create-custom-rules/add-output.png" alt-text="Screenshot of Add SandGrid Output.":::


### Test the function works

To test the function in the portal, first choose **Logs** at the bottom of the code editor. Then choose **Test** to the right of the code editor. Use the following JSON as the **Request body**:

```json
[{"deviceid":"test-device-1","time":"2019-05-02T14:23:39.527Z"},{"deviceid":"test-device-2","time":"2019-05-02T14:23:50.717Z"},{"deviceid":"test-device-3","time":"2019-05-02T14:24:28.919Z"}]

The function log messages appear in the Logs panel:


After a few minutes, the **To** email address receives an email with the following content:

```txt
The following device(s) have stopped sending telemetry:

Device ID    Time
test-device-1    2019-05-02T14:23:39.527Z
test-device-2    2019-05-02T14:23:50.717Z
test-device-3    2019-05-02T14:24:28.919Z

Add Stream Analytics query

This solution uses a Stream Analytics query to detect when a device stops sending telemetry for more than 120 seconds. The query uses the telemetry from the event hub as its input. The job sends the query results to the function app. In this section, you configure the Stream Analytics job:

In the Azure portal, navigate to your Stream Analytics job, under Jobs topology select Inputs, choose + Add stream input, and then choose Event Hub.
Use the information in the following table to configure the input using the event hub you created previously, then choose Save:

Setting Value

Input alias centraltelemetry

Subscription Your subscription

Event Hub namespace Your Event Hub namespace

Event Hub name Use existing - centralexport
Under Jobs topology, select Outputs, choose + Add, and then choose Azure Function.
Use the information in the following table to configure the output, then choose Save:

Setting Value

Output alias emailnotification

Subscription Your subscription

Function app Your function app

Function HttpTrigger1

Setting	Value
Input alias	centraltelemetry
Subscription	Your subscription
Event Hub namespace	Your Event Hub namespace
Event Hub name	Use existing - centralexport

Setting	Value
Output alias	emailnotification
Subscription	Your subscription
Function app	Your function app
Function	HttpTrigger1

Under Jobs topology, select Query and replace the existing query with the following SQL:

with
LeftSide as
(
    SELECT
    -- Get the device ID from the message metadata and create a column
    GetMetadataPropertyValue([centraltelemetry], '[EventHub].[IoTConnectionDeviceId]') as deviceid1, 
    EventEnqueuedUtcTime AS time1
    FROM
    -- Use the event enqueued time for time-based operations
    [centraltelemetry] TIMESTAMP BY EventEnqueuedUtcTime
),
RightSide as
(
    SELECT
    -- Get the device ID from the message metadata and create a column
    GetMetadataPropertyValue([centraltelemetry], '[EventHub].[IoTConnectionDeviceId]') as deviceid2, 
    EventEnqueuedUtcTime AS time2
    FROM
    -- Use the event enqueued time for time-based operations
    [centraltelemetry] TIMESTAMP BY EventEnqueuedUtcTime
)

SELECT
    LeftSide.deviceid1 as deviceid,
    LeftSide.time1 as time
INTO
    [emailnotification]
FROM
    LeftSide
    LEFT OUTER JOIN
    RightSide 
    ON
    LeftSide.deviceid1=RightSide.deviceid2 AND DATEDIFF(second,LeftSide,RightSide) BETWEEN 1 AND 120
    where
    -- Find records where a device didn't send a message 120 seconds
    RightSide.deviceid2 is NULL

Select Save.
To start the Stream Analytics job, choose Overview, then Start, then Now, and then Start:

Configure export in IoT Central

On the Azure IoT Central application manager website, navigate to the IoT Central application you created.

In this section, you configure the application to stream the telemetry from its simulated devices to your event hub. To configure the export:

Navigate to the Data Export page, select + New, and then Azure Event Hubs.

Use the following settings to configure the export, then select Save:

Setting	Value
Display Name	Export to Event Hubs
Enabled	On
Type of data to export	Telemetry
Enrichments	Enter desired key / Value of how you want the exported data to be organized
Destination	Create New and enter information for where the data will be exported

Screenshot of the Data Export.

Wait until the export status is Running before you continue.

Test

To test the solution, you can disable the continuous data export from IoT Central to simulated stopped devices:

In your IoT Central application, navigate to the Data Export page and select the Export to Event Hubs export configuration.
Set Enabled to Off and choose Save.

After at least two minutes, the To email address receives one or more emails that look like the following example content:

The following device(s) have stopped sending telemetry:

Device ID         Time
Thermostat-Zone1  2019-11-01T12:45:14.686Z

Tidy up

To tidy up after this how-to and avoid unnecessary costs, delete the DetectStoppedDevices resource group in the Azure portal.

You can delete the IoT Central application from the Management page within the application.

Next steps

In this how-to guide, you learned how to:

Stream telemetry from an IoT Central application using continuous data export.
Create a Stream Analytics query that detects when a device has stopped sending data.
Send an email notification using the Azure Functions and SendGrid services.

Now that you know how to create custom rules and notifications, the suggested next step is to learn how to Extend Azure IoT Central with custom analytics.