IoT Alerting System Powered by Azure IoT Edge, Azure Functions and Time Series Insights

Overview

IoT Alerting System helps to monitor temperature and humidity conditions to inform responsible technicians for unexpected changes in the values using time-series analysis techniques.

The project has the following architecture:

A group of devices is monitoring machine temperature and ambient humidity. On the devices are deployed two functions - one for monitoring machine temperature and another one for ambient humidity. The functions monitor if the values are above predefined threshold and if so, send the data to a IoT Hub. In the IoT Hub the data is filtered and it is sent to one of the configured Event Hubs to persist in Time Series Insights or pass it for aggregation by Azure Stream Analytics. If there are more events than predefined threshold in Azure Stream Analytics an Azure Function is triggered to send an email to the responsible technician.

A walkthrough for building the project is provided below.

Walkthrough

1. Setting Up Edge Devices

Finding and using a real IoT device is sometimes difficult so we will use Azure VM instead.

Please follow the instructions in this tutorial to deploy Azure IoT Edge runtime on Azure Linux VM.

2. Azure Function on IoT Edge

Next, we will deploy our first Azure Function that will be responsible for monitoring machines temperature. For that step follow the tutorial for deploying Azure Function to IoT Edge. You can find all required assets for this function in the folder Temperature Filter Function

Source Code for functions:


    #r "Microsoft.Azure.Devices.Client"
    #r "Newtonsoft.Json"

    using System.IO;
    using Microsoft.Azure.Devices.Client;
    using Newtonsoft.Json;

    public static async Task Run(Message messageReceived, IAsyncCollector<Message> output, TraceWriter log)
    {
        // Temperature Threshold 
        const int temperatureThreshold = 25;
        byte[] messageBytes = messageReceived.GetBytes();
        var messageString = System.Text.Encoding.UTF8.GetString(messageBytes);

        if (!string.IsNullOrEmpty(messageString))
        {
            // Get the body of the message and deserialize it
            var messageBody = JsonConvert.DeserializeObject<MessageBody>(messageString);

            // Check temperature value
            if (messageBody != null && messageBody.machine.temperature > temperatureThreshold)
            {
                // We will send the message to the output as the temperature value is greater than the threashold
                var filteredMessage = new Message(messageBytes);
                // We need to copy the properties of the original message into the new Message object
                foreach (KeyValuePair<string, string> prop in messageReceived.Properties)
                {
                    filteredMessage.Properties.Add(prop.Key, prop.Value);
                }
                // We are adding a new property to the message to indicate it is a temperature alert
                filteredMessage.Properties.Add("MessageType", "Alert");
                // Send the message        
                await output.AddAsync(filteredMessage);
                log.Info("Received and transferred a message with temperature above the threshold");
            }
        }
    }

The second function will monitor ambient humidity. You can follow the same tutorial for deploying Azure Function to IoT Edge with a few modifications:

  • In Create a function project change the function code to below. You can find all required assets for this function in the folder Humidity Filter Function:
    ...

    public static async Task Run(Message messageReceived, IAsyncCollector<Message> output, TraceWriter log)
    {
        // Threshold for Humidity
        const int humidityThreshold = 24;

        byte[] messageBytes = messageReceived.GetBytes();
        var messageString = System.Text.Encoding.UTF8.GetString(messageBytes);

        if (!string.IsNullOrEmpty(messageString))
        {
            ...

            // Check for humidity value
            if (messageBody != null && messageBody.ambient.humidity > humidityThreshold)
            {
                ...

                filteredMessage.Properties.Add("MessageType", "HumidityAlert");
                // Send the message        
                await output.AddAsync(filteredMessage);
                log.Info("Received and transferred a message with ambient humidity above the threshold");
            }
        }
    }

  • Modify the IoT Hub routes to the following configuration:
     {
      "routes": {
        "sensorToFilter": "FROM /messages/modules/tempSensor/outputs/temperatureOutput INTO BrokeredEndpoint(\"/modules/temperatureFilter/inputs/input1\")",
        "sensorToHumidityFilter": "FROM /messages/modules/tempSensor/outputs/temperatureOutput INTO BrokeredEndpoint(\"/modules/humidityFilter/inputs/input1\")",
        "filterToIoTHub": "FROM /messages/modules/temperatureFilter/outputs/* INTO $upstream",
        "humidityFilterToIoTHub": "FROM /messages/modules/humidityFilter/outputs/* INTO $upstream"
        }
      }

3. Configure IoT Hub

Next, the connections to the 3 Event Hub instances need to be configured. These Event Hub instances will be responsible for getting the data from IoT Hub and passing it along for further processing.

IoT Hub Endpoints will be defined for each of the Event Hubs as shown below:

Next, the rules for routing data to the correct IoT Hub instance are defined. The final configuration looks like:

Next configure the humidity route:

Two of the Event Hubs are connected to Stream Analytics Jobs that are aggregating the values and based on a predefined threshold trigger built using an Azure Function for sending an email.

Below is the Azure Stream Analytics job for humidity:

SELECT
    System.TimeStamp AS Time,
    COUNT(*) AS [Count]
INTO
    humidityout
FROM
    humidity TIMESTAMP BY TIMECREATED
GROUP BY
    TumblingWindow(second, 180)
HAVING
    [Count] >= 5

Below is the Azure Stream Analytics job for temperature:

SELECT
    System.TimeStamp AS Time,
    COUNT(*) AS [Count]
INTO
    AlertOutput
FROM
    temperature TIMESTAMP BY TIMECREATED
GROUP BY
    TumblingWindow(second, 180)
HAVING
    [Count] >= 5

4. Azure Functions for Alerting

An email will be sent when there are: - More than 5 elevated temperature events within a 3 minute window. - More than 5 ambient humidity events within a 3 minute window.

Azure Stream Analytics has first party integration with Azure Functions. Using Azure Function Runtime v2, follow these steps to configure your Function App. The code for the function is below:

#r "Newtonsoft.Json"
#r "SendGrid"

using System.Net;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.Primitives;
using Newtonsoft.Json; 
using SendGrid.Helpers.Mail; 
using System.Text;

public async static Task<IActionResult> Run(HttpRequest req, IAsyncCollector<SendGridMessage> messages, TraceWriter log)
{
    log.Info("SendGrid message"); 
    using (StreamReader reader = new StreamReader(req.Body, Encoding.UTF8))
    {
        var body = await reader.ReadToEndAsync();
        var message = new SendGridMessage();
        message.AddTo("technicians@iot.com");
        message.AddContent("text/html", body);
        message.SetFrom("iot@alert.com");
        message.SetSubject("[Alert] IoT Hub Notrtification");
        await messages.AddAsync(message); 
        return (ActionResult)new OkObjectResult("The E-mail has been sent.");
    }
}

Configure the function in function.json file:

    {
    "bindings": [
      {
        "authLevel": "function",
        "name": "req",
        "type": "httpTrigger",
        "direction": "in"
      },
      {
        "name": "$return",
        "type": "http",
        "direction": "out"
      },
      {
        "type": "sendGrid",
        "name": "messages",
        "apiKey": "SendGridAttribute.ApiKey",
        "direction": "out"
      }
    ],
    "disabled": false
  }

This function requires that you set a SendGrid key using the App Setting property called "SendGridAttribute.ApiKey" inside the Function App. In the Azure portal you can create free account for SendGrid with 20 000 email per month.

All the assets for the email function can be found here

5. Analyzing Data with Time Series Insights

IoT Hub sends all recieved events to an instance of Event Hub. This Event Hub is configured to be a source of data for a Time Series Insights instance:

Time Series Insights was built with IoT scenarios in mind. It combines familiar SQL syntax and powerful visualization capabilities in one product designed for massive data throughput.

Time Series Insights automatically parses the data and shows a default graph for event count:

To configure multiple queries whose graphs can overlay:

This can be done by cloning a query and modifying it. But it is recommended to plot each query on separate part of dashboard for better visibility:

Congratulations! You have just built complete IoT solution including edge logic, IoT Hub, alerting email functions and detailed data view powered by Time Series Insights!