Develop Azure Digital Twins (ADT) solutions

Lab Scenario

Contoso Management has decided to take the next step in their digital evolution and develop a model of their cheese making facility using Azure Digital Twins (ADT). With Azure Digital Twins, it is possible to create and interact with live models of real-world environments. First, each individual element is modeled as a digital twin. Then, these models are connected into a knowledge graph that can respond to live events and be queried for information.

In order to better understand how to best leverage ADT, you have been asked to build a proof-of-concept prototype that demonstrates how the existing Cheese Cave Device sensor telemetry can be incorporated into a simple model hierarchy:

  • Cheese Factory
  • Cheese Cave
  • Cheese Cave Device

In this first prototype, you have been asked to demonstrate the solutions to the following scenarios:

  • How device telemetry can be mapped from an IoT Hub into the appropriate device in ADT
  • How updates to a child digital twin property can be used to update a parent twin property (from a Cheese Cave Device to a Cheese Cave)
  • How device telemetry can be routed via ADT to Time Series Insights

The following resources will be created:

Lab 19 Architecture

In This Lab

In this lab, you will complete the following activities:

  • Configure Lab Prerequisites (required Azure resources)
  • Create and configure digital twins
    • Create a digital twin by using the supplied DTDL
    • Build ADT graph using digital twin instances
  • Implement ADT graph interactions (ADT Explorer)
    • Query the ADT Graph
    • Update properties on ADT entities in the graph
  • Integrate ADT with upstream and downstream systems
    • Ingest IoT device messages and translate messages to ADT
    • Configure ADT routes and endpoints to publish telemetry to Time Series Insights (TSI)

Lab Instructions

Exercise 1 - Configure Lab Prerequisites

Task 1 - Create resources

This lab assumes that the following Azure resources are available:

Resource Type Resource Name
Resource Group rg-az220
IoT Hub iot-az220-training-{your-id}
TSI tsi-az220-training-{your-id}
TSI Access Policy access1

To ensure these resources are available, complete the following steps.

  1. In the virtual machine environment, open a Microsoft Edge browser window, and then navigate to the following Web address:

    +++https://portal.azure.com/#create/Microsoft.Template/uri/https%3A%2F%2Fraw.githubusercontent.com%2FMicrosoftLearning%2FAZ-220-Microsoft-Azure-IoT-Developer%2Fmaster%2FAllfiles%2FARM%2Flab19.json+++

    NOTE: Whenever you see the green “T” symbol, for example +++enter this text+++, you can click the associated text and the information will be typed into the current field within the virtual machine environment.

  2. If prompted to log in to the Azure portal, enter the Azure credentials that you are using for this course.

    The Custom deployment page will be displayed.

  3. Under Project details, in the Subscription dropdown, ensure that the Azure subscription that you intend to use for this course is selected.

  4. In the Resource group dropdown, select rg-az220.

    NOTE: If rg-az220 is not listed:

    1. Under the Resource group dropdown, click Create new.
    2. Under Name, enter rg-az220.
    3. Click OK.
  5. Under Instance details, in the Region dropdown, select the region closest to you.

    NOTE: If the rg-az220 group already exists, the Region field is set to the region used by the resource group and is read-only.

  6. In the Your ID field, enter the unique ID you created in Exercise 1.

  7. In the Course ID field, enter az220.

  8. To determine the current user object ID, open the Cloud Shell and execute the following command:

     az ad signed-in-user show --query objectId -o tsv
    

    Copy the displayed object ID.

  9. In the Object ID field, enter the object ID copied from the above step.

  10. To validate the template, click Review and create.

  11. If validation passes, click Create.

    The deployment will start.

  12. Once the deployment has completed, in the left navigation area, to review any output values from the template, click Outputs.

    Make a note of the outputs for use later:

    • connectionString
    • deviceConnectionString
    • devicePrimaryKey
    • storageAccountName

The resources have now been created.

Task 2 - Verify tools

  1. In your virtual machine environment, open a Windows Command Prompt window.

  2. To display the version of Azure CLI that is installed locally, enter the following command:

     az --version
    
  3. Verify that azure-cli version 2.11.0 or later is listed.

    Azure CLI version 2.11 provides the ability to upgrade to the latest version. To upgrade, enter the following command:

     ```powershell
     az update
     ```
    

    NOTE: If Azure CLI is not installed, you must install it before you continue:

    1. Open your browser, and then navigate to the Azure CLI tools download page: Install Azure CLI

      You should be installing the latest version of the Azure CLI tools. The current version of Azure CLI (as of February 2022) is version 2.33, but be aware that new versions are released monthly, so the latest version is likely to have changed.

    2. On the Install Azure CLI page, select the install option for your OS (such as Install on Windows), and then follow the on-screen instructions to install the Azure CLI tool.

Exercise 2 - Create an instance of the Azure Digital Twins resource

In this exercise, the Azure portal will be used to create an Azure Digital Twins (ADT) instance. The connection data for Azure Digital Twins will then be stored in a text file for later use. Finally the current user will be assigned a role to allow the ADT resource to be accessed.

Task 1 - Use the Azure portal to create a resource (Azure Digital Twins)

  1. Open the Azure portal in new browser window.

  2. On the Azure portal menu, click + Create a resource.

    The New blade that opens is a front-end to the Azure Marketplace, which is a collection of all the resources you can create in Azure. The marketplace contains resources from both Microsoft and the community.

  3. In the Search the marketplace text box, type Azure Digital Twins

  4. When the option appears, select Azure Digital Twins, and then click Create.

  5. On the Create Resource pane, under Subscription, ensure that the subscription you are using for this course is selected.

    Note: Your account must have the administrator role for the subscription

  6. For the Resource group, select rg-az220.

  7. For the Resource name, enter adt-az220-training-{your-id}.

  8. In the Region dropdown, select the region where your Azure IoT Hub is provisioned (or the closest region available).

  9. Under Grant access to resource, to ensure the current user can use the Digital Twins Explorer app, check Assign Azure Digital Twins Owner Role.

    Note: To manage the elements within an instance, a user needs access to Azure Digital Twins data plane APIs. Select the suggested role above grants the current user full access to the data plane APIs. You can also use Access Control (IAM) to choose appropriate roles later. You can learn more about Azure Digital Twins Security here

  10. To review the values entered, click Review + create.

  11. To start the deployment process, click Create.

    Wait a few moments while Deployment in progress is displayed.

  12. Select Go to resource.

    You should see the Overview pane for your ADT resource, which includes a body section titled Get started with Azure Digital Twins.

Task 2 - Save the connection data to a reference file

  1. Using Notepad or a similar text editor, create a file named adt-connection.txt.

  2. Add the name of the Azure Digital Twins instance to the file - adt-az220-training-{your-id}

  3. Add the resource group to the file - rg-az220

  4. In your browser, return to the Digital Twins instance Overview pane.

  5. In the Essentials section of the pane, locate the Host name field.

  6. Hover the mouse pointer over the Host name field, use the icon than appears to the right of the value to copy the host name to the clipboard, and then paste it into the text file.

  7. In the text file, convert the host name to a connection url to your digital twins instance by adding https:// to the start of the host name.

    The modified url will be similar to:

     https://adt-az220-training-dm030821.api.eus.digitaltwins.azure.net
    
  8. Save the adt-connection.txt file.

The Azure Digital Twin resource is now created and the user account has been updated so that the resource can be accessed via APIs.

Exercise 3 - Create a graph of the models

As part of a modeling activity, analysts would consider many factors, such as the Cheese Cave Device message content, and create mappings in DTDL Property and Telemetry field definitions. In order to use these DTDL code fragments, they would be incorporated into an Interface (the top-level code item for a model). However, the Interface for a Cheese Cave Device model would form just a small part of the Azure Digital Twins environment for a Contoso Cheese Factory. As modeling an environment that represents an entire factory is beyond the scope of this course, a greatly simplified environment that focuses on a Cheese Cave Device model, an associated Cheese Cave model, and a Factory model will be considered instead. The model hierarchy is as follows:

  • Cheese Factory Interface
  • Cheese Cave Interface
  • Cheese Cave Device Interface

Considering the hierarchy of Interface definitions above, and the relationships between them, it can be said that a Cheese Factory has Cheese Caves, and a Cheese Cave has Cheese Cave Devices.

When designing the Digital Twin models for an ADT environment, it is best to use a consistent approach for creating the IDs used for the Interfaces, Schemas, and Relationships. Each entity within the environment has an @id property (it is required for Interfaces) and should uniquely identify that entity. The format of the ID value is that of a digital twin model identifier (DTMI). A DTMI has three components: scheme, path, and version. The scheme and path are separated by a colon :, while path and version are separated by a semicolon ;. The format looks like this: <scheme> : <path> ; <version>. The value for scheme within the DTMI formatted ID is always dtmi.

One example for the ID value of a Contoso cheese factory would be: dtmi:com:contoso:digital_factory:cheese_factory;1.

In this example, the scheme value is dtmi as expected and the version is set to 1. The <path> component within this ID value utilizes the following taxonomy:

  • The source of the model - com:contoso
  • The model category - digital_factory
  • The type within the category - cheese_factory

TIP: To learn more about the DTMI format, review the following resource:

Recalling the model hierarchy and relationships identified above, an example of the IDs used could be:

Interface ID
Cheese Factory Interface dtmi:com:contoso:digital_factory:cheese_factory;1
Cheese Cave Interface dtmi:com:contoso:digital_factory:cheese_factory:cheese_cave;1
Cheese Cave Device Interface dtmi:com:contoso:digital_factory:cheese_factory:cheese_cave_device;1

And the relationships between IDs could be:

Relationship ID From ID To ID
Has Caves dtmi:com:contoso:digital_factory:cheese_factory:rel_has_caves;1 dtmi:com:contoso:digital_factory:cheese_factory;1 dtmi:com:contoso:digital_factory:cheese_factory:cheese_cave;1
Has Devices dtmi:com:contoso:digital_factory:cheese_cave:rel_has_devices;1 dtmi:com:contoso:digital_factory:cheese_factory:cheese_cave;1 dtmi:com:contoso:digital_factory:cheese_factory:cheese_cave_device;1

NOTE: In Lab 3: Setup the Development Environment, you cloned the GitHub repository containing lab resources by downloading a ZIP file and extracting the contents locally. The extracted folder structure includes the following folder path:

  • Allfiles
    • Labs
      • 19-Azure Digital Twins
        • Final
          • Models

The complete models referenced in this exercise are available in this folder location.

Fore the purposes of this exercise, the interfaces have already been defined for each of the digital twins that will be used in the proof-of-concept, it is time to construct the actual graph of digital twins. The flow for building a graph is straightforward:

  • Import the model definitions
  • Create twin instances from the appropriate models
  • Create relationships between the twin instances using the defined model relationships

There are a number of ways that this flow can be achieved:

  • Using Azure CLI commands from the command-line or in scripts
  • Programmatically using one of the SDKs or directly via the REST APIs
  • Using tools such as the ADT Explorer sample

As the ADT Explorer includes rich visualization of an ADT graph, it is well suited for building out the simple model for the proof-of-concept. However, larger, more complex, models are also supported and a comprehensive bulk import/export capability helps with iterative design. During this exercise the following tasks will be completed:

  • Access the ADT Explorer (Preview) via the Azure Portal
  • Import the Contoso Cheese models
  • Use the models to create digital twins
  • Add relationships to the graph
  • Learn how to use delete twins, relationships and models from ADT
  • Bulk import a graph into ADT

Task 1 - Access the ADT Explorer

The ADT Explorer is a an application for the Azure Digital Twins service. The app connects to an Azure Digital Twins instance and provides the following features/capabilities:

  • Upload and explore models
  • Upload and edit graphs of twins
  • Visualize the twins graph with a number of layout techniques
  • Edit properties of twins
  • Run queries against the twins graph

The ADT explorer is incorporated into the Azure Portal as a preview feature and is also available as a standalone sample application. In this lab, the version incorporated into the Azure Portal will be used.

  1. Open the Azure portal in new browser window.

  2. In your browser, navigate to the Digital Twins instance Overview pane.

  3. To open the ADT Explorer in a new browser tab, click Open Azure Digital Twins Explorer (preview).

    A new browser tab hosting the ADT Explorer will open. You will see an alert indicating no results have been found - this is expected as no models have been imported.

    Note: If the new window prompts to enter the URL of your ADT instance, enter the URL value that you saved to your text editor.

    Important: If you are prompted to login, ensure you use the same account that you used when creating the Azure Digital Twins instance, otherwise you will not have access to the data plane APIs and will see errors.

The ADT Explorer sample application is now ready for use. Loading models is your next task, so don’t be alarmed if you see an error message telling you that there are no models available.

Task 2 - Import Models

In order to create Digital Twins in ADT, it is necessary to first upload models. There are a number of ways that models can be uploaded:

The first two options are more appropriate for programmatic scenarios, whereas the Azure CLI can be useful in configuration as code scenarios or “one-off” requirements. The ADT Explorer app provides an intuitive way to interact with ADT.

TIP: What is configuration as code? As configuration is written as source code (for example, scripts containing Azure CLI commands), you can use best development practices to optimise it, such as: creating reusable definitions of model uploads, parameterization, using loops to create multiple instances of the models and so on. These scripts can then be stored in source code control to ensure they are retained, version controlled, etc.

In this task, you will use Azure CLI commands and the ADT Explorer sample app to upload the models included in the Allfiles\Labs\19-Azure Digital Twins\Final\Models folder.

  1. Open a command prompt window.

  2. To ensure that you using correct Azure account credentials, login to Azure using the following command:

     az login
    
  3. To upload the Cheese Factory Interface, enter the following command:

     az dt model create --models "{file-root}\Allfiles\Labs\19-Azure Digital Twins\Final\Models\CheeseFactoryInterface.json" -n adt-az220-training-{your-id}
    

    Ensure you replace the {file-root} with the folder the companion files for this lab are located, and replace {your-id} with your unique identifier.

    If successful, output similar to the following will be displayed.

     [
         {
             "decommissioned": false,
             "description": {},
             "displayName": {
             "en": "Cheese Factory - Interface Model"
             },
             "id": "dtmi:com:contoso:digital_factory:cheese_factory;1",
             "uploadTime": "2021-03-24T19:56:53.8723857+00:00"
         }
     ]
    

    Note: If you are unable to configure the Azure CLI command, the instructions below will show you how to import a Model using the Azure Digitial Twins Explorer interface.

  4. Return to the ADT Explorer.

    TIP: Click the Refresh button in the MODELS explorer to update the list of models.

    The uploaded Cheese Factory - Interface Model should be listed:

    ADT Explorer MODEL VIEW with Factory Model

  5. To import the remaining two models using the ADT Explorer, in the MODELS explorer, click the Upload a Model icon

    ADT Explorer MODEL VIEW Upload a Model button

  6. In the Open dialog, navigate to the Models folder, select the CheeseCaveInterface.json and the CheeseCaveDeviceInterface.json files, and then click Open.

    The two files will then be uploaded to ADT and the models added. Once complete, the MODELS explorer will update and list all three models.

Now that the models are uploaded, Digital Twins can be created.

Task 3 - Creating Twins

In an Azure Digital Twins solution, the entities in your environment are represented by digital twins. A digital twin is an instance of one of your custom-defined models. It can be connected to other digital twins via relationships to form a twin graph: this twin graph is the representation of your entire environment.

Similar to models, digital twins and relationships can be created in multiple ways:

As before, the first two options are more appropriate for programmatic scenarios, whereas the Azure CLI remains useful in configuration as code scenarios or “one-off” requirements. The most intuitive way to create digital twins and relationships is via the ADT Explorer, however there are some limitations when it comes to initializing properties.

  1. Open the command line window that you used to upload the CheeseFactoryInterface model.

  2. To create a digital twin from the Cheese Factory model using the Azure CLI, enter the following command:

     az dt twin create --dt-name adt-az220-training-{your-id} --dtmi "dtmi:com:contoso:digital_factory:cheese_factory;1" --twin-id factory_1 --properties "{file-root}\Allfiles\Labs\19-Azure Digital Twins\Final\Properties\FactoryProperties.json"
    

    Ensure you replace the {file-root} with the folder the companion files for this lab are located, and replace {your-id} with your unique identifier.

    Notice the following:

    • The –dt-name value specifies the ADT twin instance.
    • The –dtmi value specifies the Cheese Factory model uploaded earlier
    • The –twin-id specifies the ID given to the digital twin
    • The –properties value provides a file path for a JSON document that will be used to initialize the twin. Alternatively, simple JSON can also be specified in-line.

    If successful, the output of the command is similar to:

     {
         "$dtId": "factory_1",
         "$etag": "W/\"09e781e5-c31f-4bf1-aed4-52a4472b0c5b\"",
         "$metadata": {
             "$model": "dtmi:com:contoso:digital_factory:cheese_factory;1",
             "FactoryName": {
                 "lastUpdateTime": "2021-03-24T21:51:04.1371421Z"
             },
             "GeoLocation": {
                 "lastUpdateTime": "2021-03-24T21:51:04.1371421Z"
             }
         },
         "FactoryName": "Contoso Cheese 1",
         "GeoLocation": {
             "Latitude": 47.64319985218156,
             "Longitude": -122.12449651580214
         }
     }
    

    Notice that the $metadata property contains an object that tracks the last time properties were updated.

  3. The FactoryProperties.json file contains the following JSON:

     {
         "FactoryName": "Contoso Cheese 1",
         "GeoLocation": {
             "Latitude": 47.64319985218156,
             "Longitude": -122.12449651580214
         }
     }
    

    The property names match the DTDL Property values declared in the Cheese Factory Interface.

    NOTE: The complex property GeoLocation is assigned via a JSON object with Latitude and Longitude properties.

  4. In a browser, return to the ADT Explorer.

  5. To display the digital twins created so far, click Run Query.

    NOTE: Queries and the Query Language will be discussed shortly.

    After a few moments, the factory_1 digital twin should be displayed in the TWIN GRAPH view.

    ADT Explorer GRAPH VIEW Factory 1

  6. To view the digital twin properties, in the TWIN GRAPH view, click factory_1.

    The properties for factory_1 are displayed in the Property View as nodes in a tree view.

  7. To view the longitude and latitude property values, click GeoLocation.

    Notice that the values are consistent with those in the FactoryProperties.json file.

  8. To create another digital twin from the Cheese Factory model, in the MODELS explorer, locate the Cheese Factory model, and then click Create a Twin

    ADT Explorer MODEL VIEW Create a Twin button

  9. When prompted for the New Twin Name enter factory_2 and then click Save.

  10. To view the digital twin properties for factory_2, in the TWIN GRAPH view, click factory_2.

    Notice that the FactoryName and GeoLocation properties are uninitialized.

  11. To set the factoryName, position the mouse cursor to the right of the property - a textbox control should appear. Enter Cheese Factory 2.

    ADT Explorer Property View enter factory name

  12. In the PROPERTIES Explorer pane, to save the update to the property, select the Patch Twin icon.

    Note: The Patch Twin icon appears identical to the Save Query icon located to the right of the Run Query button. You don’t want the Save Query icon.

    Selecting Patch Twin will result in a JSON Patch being created and sent to update the digital twin. The Patch Information will be displayed in a dialog. Notice that as this is the first time the value has been set, the op (operation) property is add. Subsequent changes to the value would be replace operations - to see this, click Run Query to refresh the TWIN GRAPH view before making another update.

    TIP: To learn more about a JSON Patch document, review the following resources:

  13. In the PROPERTIES explorer, examine the factory_2 GeoLocation property - notice the values for Latitude and Longitude are shown as Unset.

    Info: Earlier versions of the ADT Explorer did not support editing “sub-properties” via the UI - this feature is a welcome addition.

  14. Update the Latitude and Longitude values as follows:

    Property name Value
    Latitude 47.64530450740752
    Longitude -122.12594819866645
  15. In the PROPERTIES Explorer pane, to save the update to the properties, select the Patch Twin icon.

    Notice that the Patch Information is once again displayed.

  16. Add the following digital twins by selecting the appropriate model in MODELS explorer and clicking Add a Twin:

    Model Name Digital Twin Name
    Cheese Cave - Interface Model cave_1
    Cheese Cave - Interface Model cave_2
    Cheese Cave Device - Interface Model device_1
    Cheese Cave Device - Interface Model device_2

    ADT Explorer graph view displaying created twins

Now that some twins have been created, it is time to add some relationships.

Task 4 - Adding relationships

Twins are connected into a twin graph by their relationships. The relationships that a twin can have are defined as part of its model.

For example, the Cheese Factory model defines a “contains” relationship that targets twins of type Cheese Cave. With this definition, Azure Digital Twins will allow you to create rel_has_caves relationships from any Cheese Factory twin to any Cheese Cave twin (including any twins that may be subtypes of a Cheese Cave - for example a specialized Cheese Cave for a specific cheese).

The result of this process is a set of nodes (the digital twins) connected via edges (their relationships) in a graph.

Similar to Models and Twins, relationships can be created in multiple ways.

  1. To create a relationship via the Azure CLI, return to the command prompt and execute the following command:

     az dt twin relationship create -n adt-az220-training-{your-id} --relationship-id factory_1_has_cave_1 --relationship rel_has_caves --twin-id factory_1 --target cave_1
    

    Ensure you replace {your-id} with your unique identifier.

    If successful, the output of the command is similar to:

     {
         "$etag": "W/\"cdb10516-36e7-4ec3-a154-c050afed3800\"",
         "$relationshipId": "factory_1_has_cave_1",
         "$relationshipName": "rel_has_caves",
         "$sourceId": "factory_1",
         "$targetId": "cave_1"
     }
    
  2. To visualize the relationship, in a browser, return to the ADT Explorer.

  3. To display the updated digital twins, click Run Query.

    The diagram will refresh and the new relationship will be displayed.

    ADT Explorer graph view with a relationship

    If you don’t see the relationship, refresh the browser window and then run the query.

  4. To add a relationship using the ADT Explorer, first click cave_1 to select it, and then right-click device_1. In the displayed context menu, select Add relationships.

  5. In the Create Relationship dialog, under Source ID, confirm that cave_1 is displayed.

  6. Under Target ID, confirm that device_1 is displayed.

  7. Under Relationship, select rel_has_devices.

    NOTE: Unlike relationships created with the Azure CLI, there is no equivalent UI to supply a $relationshipId value. Instead, a GUID will be assigned.

  8. To Create the relationship, click Save.

    The relationship will be created and the diagram will update to display the relationship. The diagram now shows that factory_1 has cave_1, which has device_1.

  9. Add two more relationships:

    Source Target Relationship
    factory_1 cave_2 rel_has_caves
    cave_2 device_2 rel_has_devices

    The graph should now appear similar to:

    ADT Explorer graph view with updated graph

  10. To view the layout options for the TWIN GRAPH view, click the Choose Layout button.

    ADT Explorer graph view choose layout

    The TWIN GRAPH view can use different algorithms to layout the graph. The Klay layout is selected by default. You can try selecting different layouts to see how the graph is impacted.

Task 5 - Deleting models, relationships and Twins

During the design process for modeling with ADT, it is likely that a number of proof-of-concepts will be created, many of which will be deleted. Similar to the other operations on digital twins, there are programmatic approaches (API, SDK, and CLI) to deleting models and twins, and you can also use the ADT Explorer.

NOTE: One thing to note is that the delete operations are asynchronous and although, for example, a REST API call or a delete in ADT Explorer may appear to complete instantly, it may take a few minutes for the operation to complete within the ADT service. Attempting to upload revised models with the same name as recently deleted models may fail unexpectedly until the back-end operations have completed.

  1. To delete the factory_2 digital twin via the CLI, return to your command prompt window, and then enter the following command:

     az dt twin delete -n adt-az220-training-{your-id} --twin-id factory_2
    

    Unlike other commands, no output is displayed (unless the command produces an error).

  2. To delete the relationship between factory_1 and cave_1, enter the following command:

     az dt twin relationship delete -n adt-az220-training-{your-id} --twin-id factory_1 --relationship-id factory_1_has_cave_1
    

    Notice that this command requires the relationship ID. You can view the relationship IDs for a given twin. For example, to view the relationship IDs for factory_1, you can enter the following command:

     az dt twin relationship list -n adt-az220-training-{your-id} --twin-id factory_1
    

    If you ran this command prior to deleting the relationship to cave 1, you would see output similar to the following:

     [
         {
             "$etag": "W/\"a6a9f506-3cfa-4b62-bcf8-c51b5ecc6f6d\"",
             "$relationshipId": "47b0754a-25d1-4b71-ac47-c2409bb08535",
             "$relationshipName": "rel_has_caves",
             "$sourceId": "factory_1",
             "$targetId": "cave_2"
         },
         {
             "$etag": "W/\"b5207e88-7c86-498f-a272-7f81dde88dee\"",
             "$relationshipId": "factory_1_has_cave_1",
             "$relationshipName": "rel_has_caves",
             "$sourceId": "factory_1",
             "$targetId": "cave_1"
         }
     ]
    
  3. To delete a model, enter the following command:

     az dt model delete -n adt-az220-training-{your-id} --dtmi "dtmi:com:contoso:digital_factory:cheese_factory;1"
    

    Again no output is displayed.

    IMPORTANT: This command deleted the factory model and succeeded, even though a digital twin factory_1 still exists. Digital twins that were created using the deleted model can still be found by querying the graph, however, properties of the twin can no longer be updated without the model. Be very careful when completing model management tasks (versioning, deleting, etc.) to avoid creating inconsistent graphs.

  4. To display the recent changes to the digital twins, return to the ADT Explorer.

  5. To update the display, refresh the browser page and then click Run Query.

    The Cheese Factory model should be missing from the MODELS explorer and there should be no relationship between factory_1 and cave_1 in the TWIN GRAPH view.

  6. To select the relationship between cave_1 and device_1, click the line between the two twins.

    The line should thicken indicating it is selected and the Delete Relationship button will be enabled.

    ADT Explorer graph view delete relationship

  7. To delete the relationship, right-lick the line and select Delete relationship(s) from the context menu, and confirm by clicking Delete.

    The relationship will be deleted and the graph will update.

  8. To delete the device_1 digital twin, right-click device_1, and select Delete twin(s) from the context menu.

    NOTE: By using CTRL and left-click, multiple twins can be selected. To delete them, right-click the final twin and select Delete twin(s) from the context menu.

  9. In the upper-right corner of the ADT Explorer page, to delete all of the digital twins in a graph, click Delete All Twins, and confirm by clicking Delete.

    ADT Explorer delete all twins

    IMPORTANT: Use with care - there is no undo this capability!

  10. To delete the Cheese Cave Device model from the MODELS explorer, click the associated Delete Model button, and confirm by clicking Delete.

  11. To delete all models, click Delete All Models at the top of the MODELS explorer.

    IMPORTANT: Use with care - there is no undo capability!

At this point, the ADT instance should be clear of all models, twins and relationships. Don’t worry - in the next task the Import Graph feature will be used to create a new graph.

Task 6 - Bulk import with ADT Explorer

The ADT Explorer supports the import and export of a digital twin graph. The Export capability serializes the most recent query results to a JSON-based format, including models, twins, and relationships. The Import capability deserializes from either a custom Excel-based format or the JSON-based format generated on export. Before import is executed, a preview of the graph is presented for validation.

The excel import format is based on the following columns:

  • ModelId: The complete dtmi for the model that should be instantiated.
  • ID: The unique ID for the twin to be created
  • Relationship: A twin id with an outgoing relationship to the new twin
  • Relationship name: The name for the outgoing relationship from the twin in the previous column
  • Init data: A JSON string that contains Property settings for the twins to be created

NOTE: The Excel import capability does not import model definitions, only twins and relationships. The JSON format supports models as well.

The following table shows the twins and relationships that will be created in this task (the Init Data values are removed for readability):

ModelID ID Relationship (From) Relationship Name Init Data
dtmi:com:contoso:digital_factory:cheese_factory;1 factory_1      
dtmi:com:contoso:digital_factory:cheese_factory:cheese_cave;1 cave_1 factory_1 rel_has_caves  
dtmi:com:contoso:digital_factory:cheese_factory:cheese_cave;1 cave_2 factory_1 rel_has_caves  
dtmi:com:contoso:digital_factory:cheese_factory:cheese_cave;1 cave_3 factory_1 rel_has_caves  
dtmi:com:contoso:digital_factory:cheese_factory:cheese_cave_device;1 sensor-th-0055 cave_1 rel_has_devices  
dtmi:com:contoso:digital_factory:cheese_factory:cheese_cave_device;1 sensor-th-0056 cave_2 rel_has_devices  
dtmi:com:contoso:digital_factory:cheese_factory:cheese_cave_device;1 sensor-th-0057 cave_3 rel_has_devices  

The spreadsheet cheese-factory-scenario.xlsx can be found in the {file-root}\Allfiles\Labs\19-Azure Digital Twins\Final\Models folder.

  1. In a browser, return to the ADT Explorer.

  2. To import your models using the ADT Explorer, in the MODELS explorer, click the Upload a Model icon

  3. In the Open dialog, navigate to the Models folder, select the CheeseFactoryInterface.json, CheeseCaveInterface.json, and CheeseCaveDeviceInterface.json files, and then click Open.

    This will reload all of the models.

  4. To import the cheese-factory-scenario.xlsx spreadsheet, click Import Graph.

    ADT Explorer graph view import graph

  5. In the Open dialog, navigate to the Models folder and select the cheese-factory-scenario.xlsx file, then click Open.

    A preview of the graph to be imported is displayed in an IMPORT view:

    ADT Explorer graph view import preview

  6. To complete the import, click Start Import.

    An Import Successful dialog will be displayed, detailing that 7 twins and 6 relationships were imported. Click Close to proceed.

  7. Return to the TWIN GRAPH view, and click Run Query.

    The imported graph should now be displayed. You can click on each twin to view the properties (each twin has been initialized with values).

  8. To export the current graph as JSON, click Export Graph (next to the Import Graph button used earlier).

    The Export view is displayed with a Download link in the top-left corner.

  9. To download the model in JSON, click the Download link.

    The browser will download the model.

  10. To view the JSON, open the downloaded file in Visual Studio Code.

    If the JSON is shown as a single line, reformat the JSON using the Format Document command via the command palette or by pressing SHIFT+ALT+F.

    The JSON has three primary sections:

    • digitalTwinsFileInfo - contains the version of the exported file format
    • digitalTwinsGraph - contains the instance data for every twin and relationship that was displayed on the exported graph (i.e. only those displayed based upon the query)
    • digitalTwinsModels - the model definitions

    NOTE: Unlike the Excel format, the JSON file includes the model definitions, meaning that everything can be imported with just the one file.

  11. To import the JSON file, use ADT Explorer to delete the models and twins following the instructions in earlier tasks, and then import the JSON export file that was just created. Note that the models, twins and their properties, and the relationships are recreated.

This twin graph will be used as the basis for the exercise on querying.

Exercise 4 - Query the graph using ADT Explorer

NOTE: This exercise requires the graph imported in the previous exercise.

Now let’s review the digital twin graph query language.

You can query the digital twin graph that you just built, to get information about the digital twins and relationships it contains. You write these queries in a custom, SQL-like query language, referred to as the Azure Digital Twins query language. This language is also similar to the query language for Azure IoT Hub.

Queries can be made through the Digital Twins REST API and with the SDKs. In this exercise, you’ll be using the Azure Digital Twins explorer sample app to handle the API calls for you. Additional tools will be explored later in this lab.

NOTE: The ADT Explorer is designed to visualize a graph and can only display entire twins, rather than just single values selected from a twin, such as the name.

Task 1 - Query using the ADT Explorer

In this task, the ADT Explorer will be used to execute graph queries and render the results as a graph. Twins can be queried by properties, model type and by relationships. Queries can be combined into compound queries using combination operators that can query for more than one type of twin descriptor at a a time.

  1. In a browser, return to the ADT Explorer.

  2. Ensure the QUERY EXPLORER query is set to the following:

     SELECT * FROM digitaltwins
    

    If you are at all familiar with SQL, you will expect that this will return everything from digital twins.

  3. To run this query, click Run Query.

    As expected, the entire graph is displayed.

  4. To save this as a named query, click on the Save icon (just to the right of the Run Query button).

  5. In the Save Query dialog, enter the name All Twins and click Save.

    This query will then be saved locally and be available in the Saved Queries drop down to the left of the query text box. To delete a saved query, click on the X icon next to the name of the query when the Saved Queries drop down is open.

    TIP: Run the All Twins query to return to the full view at any time.

  6. To filter the graph so that only Cheese Cave twins are displayed, enter and run the following query:

     SELECT * FROM digitaltwins
     WHERE IS_OF_MODEL('dtmi:com:contoso:digital_factory:cheese_factory:cheese_cave;1')
    

    The graph will now display just the 3 Cheese Cave twins.

    Save this query as Just Caves.

  7. To display only the Cheese Cave twins that are inUse, enter and run the following query:

     SELECT * FROM digitaltwins
     WHERE IS_OF_MODEL('dtmi:com:contoso:digital_factory:cheese_factory:cheese_cave;1')
     AND inUse = true
    

    The graph should now display just cave_3 and cave_1.

  8. To display only the Cheese Cave twins that are inUse and have a temperatureAlert, enter and run the following query:

     SELECT * FROM digitaltwins
     WHERE IS_OF_MODEL('dtmi:com:contoso:digital_factory:cheese_factory:cheese_cave;1')
     AND inUse = true
     AND temperatureAlert = true
    

    The graph should now display just cave_3.

  9. To use relationships to find the parent of the device sensor-th-0055 via a join, enter the following query:

     SELECT Parent FROM digitaltwins Parent
     JOIN Child RELATED Parent.rel_has_devices
     WHERE Child.$dtId = 'sensor-th-0055'
    

    The cave_1 twin should be displayed.

    For those familiar with the SQL JOIN, the syntax used here will look different from what you might be used to. Notice that the name of the relationship rel_has_devices is specified, rather than correlating this JOIN with a key value in a WHERE clause or specifying a key value inline with the JOIN definition. This correlation is computed automatically, as the relationship properties themselves identify the target entity. Here is the relationship definition:

     {
         "@type": "Relationship",
         "@id": "dtmi:com:contoso:digital_factory:cheese_cave:rel_has_devices;1",
         "name": "rel_has_devices",
         "displayName": "Has devices",
         "target": "dtmi:com:contoso:digital_factory:cheese_factory:cheese_cave_device;1"
     }
    

Task 2 - Query for properties using the ADT Explorer

A key limitation of the ADT Explorer is is that it is designed to render a graph and the primary display cannot show the results for queries that return just properties. In this task, you will learn how it is possible to see the results of such queries without resorting to coding solutions.

  1. To run a valid query that returns just a property, enter the following query and click Run Query:

     SELECT Parent.desiredTemperature FROM digitaltwins Parent
     JOIN Child RELATED Parent.rel_has_devices
     WHERE Child.$dtId = 'sensor-th-0055'
    

    Despite the fact that the query will run without error, no graph is displayed. However, there is a way to view the results in ADT Explorer, and you will open the Output pane to view the query results in the next task.

  2. To open the Output pane, click the Settings icon at the top-right of the page.

  3. On the dialog that appears, under View, enable Output, and then close the dialog.

    The Output pane should appear at the bottom of the page.

  4. Rerun the query above and review the contents of the Output pane.

    The OUTPUT pane should display the Requested query, and then show the returned JSON. The JSON should be similar to the following:

     {
         "queryCharge": 20.259999999999998,
         "connection": "close",
         "content-encoding": "gzip",
         "content-type": "application/json; charset=utf-8",
         "date": "Thu, 25 Mar 2021 21:34:40 GMT",
         "strict-transport-security": "max-age=2592000",
         "traceresponse": "00-182f5e54efb95c4b8b3e2a6aac15499f-9c5ffe6b8299584e-01",
         "transfer-encoding": "chunked",
         "vary": "Accept-Encoding",
         "x-powered-by": "Express",
         "value": [
             {
             "desiredTemperature": 50
             }
         ],
         "continuationToken": null
     }
    

    Along with additional result metadata, notice that the value property contains the selected desiredTemperature property and value.

Exercise 5 - Configure and launch device simulator

In the preceding exercises, the digital twin model and graph for the proof-of-concept were created. In order to demonstrate how to route device message traffic from IoT Hub to ADT, it is useful to use a device simulator. In this exercise, you will be configuring a simulated device app to send telemetry to your IoT Hub.

Task 1: Open the device simulator project

In this task, the Cheese Cave Device simulator app will be opened in Visual Studio Code in preparation for configuration.

  1. Open Visual Studio Code.

  2. On the File menu, click Open Folder

  3. In the Open Folder dialog, navigate to the lab 19 Starter folder.

    In Lab 3: Setup the Development Environment, you cloned the GitHub repository containing lab resources by downloading a ZIP file and extracting the contents locally. The extracted folder structure includes the following folder path:

    • Allfiles
      • Labs
        • 19-Azure Digital Twins
          • Starter
            • CheeseCaveDevice
  4. Click CheeseCaveDevice, and then click Select Folder.

    You should see the following files listed in the EXPLORER pane of Visual Studio Code:

    • CheeseCaveDevice.csproj
    • Program.cs
  5. To open the code file, click Program.cs.

    A cursory glance will reveal that this application is very similar to the simulated device applications that you have worked on in the preceding labs. This version uses symmetric Key authentication, sends both telemetry and logging messages to the IoT Hub, and has a more complex sensor implementation.

  6. On the Terminal menu, click New Terminal.

    Notice the directory path indicated as part of the command prompt. You do not want to start building this project within the folder structure of a previous lab project.

  7. At the terminal command prompt, to verify the application builds, enter the following command:

     dotnet build
    

    The output will be similar to:

     > dotnet build
     Microsoft (R) Build Engine version 16.5.0+d4cbfca49 for .NET Core
     Copyright (C) Microsoft Corporation. All rights reserved.
    
     Restore completed in 39.27 ms for D:\Az220\AllFiles\Labs\19-Azure Digital Twins\Starter\CheeseCaveDevice\CheeseCaveDevice.csproj.
     CheeseCaveDevice -> D:\Az220\AllFiles\Labs\19-Azure Digital Twins\Starter\CheeseCaveDevice\bin\Debug\netcoreapp3.1\CheeseCaveDevice.dll
    
     Build succeeded.
         0 Warning(s)
         0 Error(s)
    
     Time Elapsed 00:00:01.16
    

In the next task, you will configure the connection string and review the application.

Task 2: Configure connection and review code

The simulated device app that you will build in this task simulates an IoT device that monitors temperature and humidity. The app will simulate sensor readings and communicate sensor data every two seconds and is the same app that was built in Lab 15.

  1. In Visual Studio Code, ensure that the Program.cs file is open.

  2. In the code editor, locate the following line of code:

     private readonly static string deviceConnectionString = "<your device connection string>";
    
  3. Replace the <your device connection string> with the device connection string that you saved near the end of the lab setup exercise.

    This is the only change that you need to implement before sending telemetry to the IoT Hub.

    NOTE: You saved both a Device and Service connection string. Be sure to provide the Device connection string.

  4. On the File menu, click Save.

Task 3: Test your Code to Send Telemetry

In this task, the configured simulator app is launched and the the successful transmission of telemetry is verified.

  1. In Visual Studio Code, ensure that you still have the Terminal open.

  2. At the Terminal command prompt, to run the simulated device app, enter the following command:

     dotnet run
    

    This command will run the Program.cs file in the current folder.

  3. Notice the output being sent to the Terminal.

    You should quickly see console output, similar to the following:

    Console Output

    Note: Green text is used to indicate when things are working as they should be. Red text is used to indicate when there is a problem. If you don’t get a screen similar to the image above, start by checking your device connection string.

  4. Leave this app running.

    You need to be sending telemetry to IoT Hub later in this lab.

Exercise 6 - Set up Azure Function to ingest data

A key part of the proof-of-concept is to demonstrate how data from a device can be delivered to Azure Digital Twins. Data can be ingested into Azure Digital Twins through external compute resources such as Virtual Machines, Azure Functions, and Logic Apps. In this exercise, a function app will be invoked by an IoT Hub’s built-in Event Grid. The function app receives the data and uses the Azure Digital Twins APIs to set properties on the appropriate digital twin instance.

Task 1 - Create and configure a function app

In order to configure an IoT Hub event grid endpoint to route telemetry to an Azure Function, it is necessary to first create the Azure Function. In this task, an Azure Function App is created that provides the execution context in which individual Azure Functions run.

In order to access Azure Digital Twins and it’s APIs, it is necessary to utilize a service principal with the appropriate permissions. During this task, a service principal is created for the function app and then assigned the appropriate permission. Once the function app has the appropriate permission, any Azure Functions that execute within the function app context will use that service principal and will therefore have permission to access ADT.

The function app context also provides an environment for managing app settings for one or more functions. This capability will be used to define a setting that contains the ADT connection string which can then be read by the Azure Functions. Encapsulating connection strings and other configurations values in app settings is considered a much better practice than hard-coding the values in the function code.

  1. Open the browser window containing your Azure portal, and then open the Azure Cloud Shell.

  2. At the Cloud Shell command prompt, to create an Azure Function App, enter the following command:

     az functionapp create --resource-group rg-az220 --consumption-plan-location {your-location} --name func-az220-hub2adt-training-{your-id} --storage-account staaz220training{your-id} --functions-version 3
    

    Note: Remember to replace the {your-location} and {your-id} tokens above.

    The Azure function requires that a bearer token to be passed to it in order to authenticate with Azure Digital Twins. To make sure that this token is passed, you’ll need to create a managed identity for the function app.

  3. To create (assign) the system-managed identity for the function app and display the associated principal Id, enter the following command:

     az functionapp identity assign -g rg-az220 -n func-az220-hub2adt-training-{your-id} --query principalId -o tsv
    

    Note: Remember to replace the {your-id} token above.

    The output will be similar to following:

     1179da2d-cc37-48bb-84b3-544cbb02d194
    

    This is the principal ID that was assigned to the function app - you will need the principal ID in the next step.

  4. To assign the Azure Digital Twins Data Owner role to the Function App principal, enter the following command:

     az dt role-assignment create --dt-name adt-az220-training-{your-id} --assignee {principal-id} --role "Azure Digital Twins Data Owner"
    

    Note: Remember to replace the {your-id} and {principal-id} tokens above. The {principal-id} value was displayed as the output of the previous step.

    Now that the principal has been assigned to the Azure Function App, that principal must be assigned the Azure Digital Twins Data Owner role so that is can access the Azure Digital Twins instance.

  5. In order to supply the Azure Digital Twin instance URL to the Azure Function App as an environment variable, enter the following command:

     az functionapp config appsettings set -g rg-az220 -n func-az220-hub2adt-training-{your-id} --settings "ADT_SERVICE_URL={adt-url}"
    

    Note: Remember to replace the {your-id} and {adt-url} tokens above. The {adt-url} value was saved to the adt-connection.txt file in an earlier task and will be similar to https://adt-az220-training-dm030821.api.eus.digitaltwins.azure.net.

    Once complete, the command lists all of the available settings. The Azure Function will now be able to obtain the ADT service URL by reading the ADT_SERVICE_URL value.

Task 2 - Review Contoso.AdtFunctions Project

In this task you will review the Azure Function that will be executed whenever an event occurs on the associated Event Grid. The event will be processed and the message and telemetry will be routed to ADT.

  1. In Visual Studio Code, open the Contoso.AdtFunctions folder.

  2. Open the Contoso.AdtFunctions.csproj file.

NOTE: In Lab 3: Setup the Development Environment, you cloned the GitHub repository containing lab resources by downloading a ZIP file and extracting the contents locally. The extracted folder structure includes the following folder path:

  • Allfiles
    • Labs
      • 19-Azure Digital Twins
        • Final
          • Contoso.AdtFunctions
Notice the project references the following NuGet Packages:

* The **Azure.DigitalTwins.Core** package contains the SDK for the Azure Digital Twins service. This library provides access to the Azure Digital Twins service for managing twins, models, relationships, etc.
* The **Microsoft.Azure.WebJobs.Extensions.EventGrid** package provides functionality for receiving Event Grid webhook calls in Azure Functions, allowing you to easily write functions that respond to any event published to Event Grid.
* The **Microsoft.Azure.WebJobs.Extensions.EventHubs** package provides functionality for receiving Event Hub webhook calls in Azure Functions, allowing you to easily write functions that respond to any event published to Event Hub.
* The **Microsoft.NET.Sdk.Functions** packages includes a build task for building .NET function projects.
* The **Azure.identity** package contains the implementation of the Azure SDK Client Library for Azure Identity. The Azure Identity library provides Azure Active Directory token authentication support across the Azure SDK. It provides a set of TokenCredential implementations which can be used to construct Azure SDK clients which support AAD token authentication
* The **System.Net.Http** package provides a programming interface for modern HTTP applications, including HTTP client components that allow applications to consume web services over HTTP and HTTP components that can be used by both clients and servers for parsing HTTP headers.
  1. In Visual Studio Code, open the HubToAdtFunction.cs file.

  2. To review the member variables for the function, locate the // INSERT member variables below here comment and review the code below it:

     //Your Digital Twins URL is stored in an application setting in Azure Functions.
     private static readonly string adtInstanceUrl = Environment.GetEnvironmentVariable("ADT_SERVICE_URL");
     private static readonly HttpClient httpClient = new HttpClient();
    

    Notice that the adtInstanceUrl variable is assigned the value of the ADT_SERVICE_URL environment variable defined earlier in the exercise. The code also follows a best practice of using a single, static, instance of the HttpClient.

  3. Locate the Run method declaration, review the following comments:

     [FunctionName("HubToAdtFunction")]
     public async static Task Run([EventGridTrigger] EventGridEvent eventGridEvent, ILogger log)
    

    Notice the use of the FunctionName attribute to mark the Run method as the entry point Run for HubToAdtFunction. The method is also declared async as the code to update the Azure Digital Twin runs asynchronously.

    The eventGridEvent parameter is assigned the Event Grid event that triggered the function call and the log parameter provides access to a logger that can be used for debugging.

    TIP: To learn more about the Azure Event Grid trigger for Azure Functions, review the resource below:

  4. To review how to log informational data, locate the following code:

     log.LogInformation(eventGridEvent.Data.ToString());
    

    The ILogger interface is defined in the Microsoft.Extensions.Logging namespace and aggregates most logging patterns to a single method call. In this case, a log entry is created at the Information level - other methods exists for various levels including critical, error. etc. As the Azure Function is running in the cloud, logging is essential during development and production.

    TIP: To learn more about the Microsoft.Extensions.Logging capability, review the following resources:

  5. Locate the following code to understand how the adtInstanceUrl variable value is checked:

     if (adtInstanceUrl == null)
     {
         log.LogError("Application setting \"ADT_SERVICE_URL\" not set");
         return;
     }
    

    This code checks if the adtInstanceUrl variable has been set - if not, the error is logged and the function exits. This demonstrates the value of logging to capture the fact that the function has been incorrectly configured.

  6. To ensure any exceptions are logged, a try..catch loop is used:

     try
     {
         // ... main body of code
     }
     catch (Exception e)
     {
         log.LogError(e.Message);
     }
    

    Notice that the exception message is logged.

  7. To see how the function app principal is used to authenticate to ADT and create a client instance, locate the // REVIEW authentication code below here comment and review the following code:

     ManagedIdentityCredential cred = new ManagedIdentityCredential("https://digitaltwins.azure.net");
     DigitalTwinsClient client = new DigitalTwinsClient(new Uri(adtInstanceUrl), cred, new DigitalTwinsClientOptions { Transport = new HttpClientTransport(httpClient) });
     log.LogInformation($"Azure digital twins service client connection created.");
    

    Notice the use of the ManagedIdentityCredential class. This class attempts authentication using the managed identity that has been assigned to the deployment environment earlier. Once the credential is returned, it is used to construct an instance of the DigitalTwinsClient. The client contains methods to retrieve and update digital twin information, like models, components, properties and relationships.

  8. To review the code that starts to process the Event Grid event, locate the // REVIEW event processing code below here comment and review the following code below it:

     if (eventGridEvent != null && eventGridEvent.Data != null)
     {
         // Read deviceId and temperature for IoT Hub JSON.
         JObject deviceMessage = (JObject)JsonConvert.DeserializeObject(eventGridEvent.Data.ToString());
         string deviceId = (string)deviceMessage["systemProperties"]["iothub-connection-device-id"];
         var fanAlert = (bool)deviceMessage["properties"]["fanAlert"]; // cast directly to a bool
         var temperatureAlert = deviceMessage["properties"].SelectToken("temperatureAlert") ?? false; // JToken object
         var humidityAlert = deviceMessage["properties"].SelectToken("humidityAlert") ?? false; // JToken object
         log.LogInformation($"Device:{deviceId} fanAlert is:{fanAlert}");
         log.LogInformation($"Device:{deviceId} temperatureAlert is:{temperatureAlert}");
         log.LogInformation($"Device:{deviceId} humidityAlert is:{humidityAlert}");
    
         var bodyJson = Encoding.ASCII.GetString((byte[])deviceMessage["body"]);
         JObject body = (JObject)JsonConvert.DeserializeObject(bodyJson);
         log.LogInformation($"Device:{deviceId} Temperature is:{body["temperature"]}");
         log.LogInformation($"Device:{deviceId} Humidity is:{body["humidity"]}");
     }
    

    Notice the use of JSON deserialization to access the event data. The event data JSON will be similar to:

     {
         "properties": {
             "sensorID": "S1",
             "fanAlert": "false",
             "temperatureAlert": "true",
             "humidityAlert": "true"
         },
         "systemProperties": {
             "iothub-connection-device-id": "sensor-th-0055",
             "iothub-connection-auth-method": "{\"scope\":\"device\",\"type\":\"sas\",\"issuer\":\"iothub\",\"acceptingIpFilterRule\":null}",
             "iothub-connection-auth-generation-id": "637508617957275763",
             "iothub-enqueuedtime": "2021-03-11T03:27:21.866Z",
             "iothub-message-source": "Telemetry"
         },
         "body": "eyJ0ZW1wZXJhdHVyZSI6OTMuOTEsImh1bWlkaXR5Ijo5OC4wMn0="
     }
    

    The message properties and systemProperties are easily accessible using an indexer approach, however where properties are optional, such as temperatureAlert and humidityAlert, the use of SelectToken and a null-coalescing operation is required to prevent an exception being thrown.

    TIP: To learn more about the null-coalescing operator ??, review the following content:

    The message body contains the telemetry payload and is ASCII encoded JSON. Therefore, it must first be decoded and then deserialized before the telemetry properties can be accessed.

    TIP: To learn more about the event schema, review the following resource:

  9. To inspect the code that updates the ADT twin, locate the // REVIEW ADT update code below here comment and review the following code below it:

     //Update twin
     var patch = new Azure.JsonPatchDocument();
     patch.AppendReplace<bool>("/fanAlert", fanAlert); // already a bool
     patch.AppendReplace<bool>("/temperatureAlert", temperatureAlert.Value<bool>()); // convert the JToken value to bool
     patch.AppendReplace<bool>("/humidityAlert", humidityAlert.Value<bool>()); // convert the JToken value to bool
    
     await client.UpdateDigitalTwinAsync(deviceId, patch);
    
     // publish telemetry
     await client.PublishTelemetryAsync(deviceId, null, bodyJson);
    

    There are two approaches being used to apply data to the digital twin - the first via property updates using a JSON patch, the second via the publishing of telemetry data.

    The ADT client utilizes a JSON Patch document to add or update digital twin properties. The JSON Patch defines a JSON document structure for expressing a sequence of operations to apply to a JSON document. The various values are added to the patch as append or replace operations, and the ADT is then updated asynchronously.

    TIP: To learn more about a JSON Patch document, review the following resources:

    IMPORTANT: The digital twin instance must have existing values before the AppendReplace operation is used.

    Notice that the telemetry data is handled differently than the properties - rather than being used to set digital twin properties, it is instead being published as telemetry events. This mechanism ensures that the telemetry is available to be consumed by any downstream subscribers to the digital twins event route.

    NOTE: The digital twins event route must be defined before publishing a telemetry message, otherwise the message will not be routed for consumption.

The function is ready to be published.

NOTE: The TelemetryFunction.cs function will be reviewed in a later task.

Task 3 - Publish Functions

  1. In the Azure Functions extension for Visual Studio Code, select Deploy to Function App:

    Visual Studio Code deploy to function app

  2. When prompted, make these selections:

    • Sign in to Azure: If prompted, sign into Azure
    • Select subscription: If prompted, select the subscription you are using for this course.
    • Select Function App in Azure: Select func-az220-hub2adt-training-{your-id}.

    When asked to confirm the deploy, click Deploy.

    The function will then be compiled and, if successful, deployed. This may take a few moments.

  3. Once the deployment has completed, the following prompt will be displayed:

    Visual Studio Code deployment complete - select stream logs

    Click Stream logs and in the confirmation dialog to enable application logging, click Yes.

    The OUTPUT pane will now display the log stream for the deployed function - this will timeout after 2 hours. There will be some status information displayed, however there will not be any diagnostic information from the function itself until it is launched. That will be covered in the next exercise.

    The streaming can be stopped or started at any time by right-clicking the Azure function in Visual Studio Code and select Start Streaming Logs or Stop Streaming Logs:

    Visual Studio Code Azure Function start streaming logs

Exercise 7 - Connect IoT Hub to the Azure Function

In this exercise, the IoT Hub created by the setup script will be configured to publish events as they occur to the Azure Function created in the previous exercise. The telemetry from the device simulator created earlier will then be routed to the ADT instance.

  1. Open a browser and navigate to the Azure portal.

  2. Navigate to the iot-az220-training-{your-id} IoT Hub.

  3. In the left-hand navigation area, select Events.

  4. To add an event subscription, click + Event Subscription.

  5. In the EVENT SUBSCRIPTION DETAILS section, in the Name field, enter device-telemetry.

  6. In the Event Grid Schema dropdown, ensure Event Grid Schema is selected.

  7. In the TOPIC DETAILS section, verify that the Topic Type is set to IoT Hub and the Source Resource is set to iot-az220-training-{your-id}.

  8. In the System Topic Name field, enter Twin-Topic

  9. In the EVENT TYPES section, in the Filter to Event Types dropdown, select only Device Telemetry.

  10. In the ENDPOINT DETAILS section, in the Endpoint Type dropdown, select Azure Function.

    Notice that the UI updates to provide for the selection of an endpoint.

  11. In the Endpoint field, click Select an endpoint.

  12. In the Select Azure Function pane, under Subscription, ensure the correct subscription is selected.

  13. Under Resource group, ensure rg-az220 is selected.

  14. Under Function app, select func-az220-hub2adt-training-{your-id}.

  15. Under Slot, confirm Production is selected.

  16. Under Function, confirm HubToAdtFunction is selected.

  17. To choose this endpoint, click Confirm Selection.

  18. Verify that HubToAdtFunction is now the specified Endpoint.

    On the Create Event Subscription pane, in the ENDPOINT DETAILS section, the Endpoint field should now display HubToAdtFunction.

  19. To create this event subscription, click Create.

    After the subscription has been created, you should see messages in the Azure Functions log stream that you configured in the preceding exercise. The Azure Functions log stream shows the telemetry being received from Event Grid. It also shows any errors that occur when connecting to Azure Digital Twins or updating the twin.

    The log output for a successful function call will be similar to:

     2021-03-12T19:14:17.180 [Information] Executing 'HubToAdtFunction' (Reason='EventGrid trigger fired at 2021-03-12T19:14:17.1797847+00:00', Id=88d9f9e8-5cfa-4a20-a4cb-36e07a78acd6)
     2021-03-12T19:14:17.180 [Information] {
     "properties": {
         "sensorID": "S1",
         "fanAlert": "false",
         "temperatureAlert": "true",
         "humidityAlert": "true"
     },
     "systemProperties": {
         "iothub-connection-device-id": "sensor-th-0055",
         "iothub-connection-auth-method": "{\"scope\":\"device\",\"type\":\"sas\",\"issuer\":\"iothub\",\"acceptingIpFilterRule\":null}",
         "iothub-connection-auth-generation-id": "637508617957275763",
         "iothub-enqueuedtime": "2021-03-12T19:14:16.824Z",
         "iothub-message-source": "Telemetry"
     },
     "body": "eyJ0ZW1wZXJhdHVyZSI6NjkuNDcsImh1bWlkaXR5Ijo5Ny44OX0="
     }
     2021-03-12T19:14:17.181 [Information] Azure digital twins service client connection created.
     2021-03-12T19:14:17.181 [Information] Device:sensor-th-0055 fanAlert is:False
     2021-03-12T19:14:17.181 [Information] Device:sensor-th-0055 temperatureAlert is:true
     2021-03-12T19:14:17.181 [Information] Device:sensor-th-0055 humidityAlert is:true
     2021-03-12T19:14:17.181 [Information] Device:sensor-th-0055 Temperature is:69.47
     2021-03-12T19:14:17.181 [Information] Device:sensor-th-0055 Humidity is:97.89
     2021-03-12T19:14:17.182 [Information] Executed 'HubToAdtFunction' (Succeeded, Id=88d9f9e8-5cfa-4a20-a4cb-36e07a78acd6, Duration=2ms)
    

    Here is an example log if the Digital Twin instance is not found:

     2021-03-11T16:35:43.646 [Information] Executing 'HubToAdtFunction' (Reason='EventGrid trigger fired at 2021-03-11T16:35:43.6457834+00:00', Id=9f7a3611-0795-4da7-ac8c-0b380310f4db)
     2021-03-11T16:35:43.646 [Information] {
     "properties": {
         "sensorID": "S1",
         "fanAlert": "false",
         "temperatureAlert": "true",
         "humidityAlert": "true"
     },
     "systemProperties": {
         "iothub-connection-device-id": "sensor-th-0055",
         "iothub-connection-auth-method": "{\"scope\":\"device\",\"type\":\"sas\",\"issuer\":\"iothub\",\"acceptingIpFilterRule\":null}",
         "iothub-connection-auth-generation-id": "637508617957275763",
         "iothub-enqueuedtime": "2021-03-11T16:35:43.279Z",
         "iothub-message-source": "Telemetry"
     },
     "body": "eyJ0ZW1wZXJhdHVyZSI6NjkuNzMsImh1bWlkaXR5Ijo5OC4wOH0="
     }
     2021-03-11T16:35:43.646 [Information] Azure digital twins service client connection created.
     2021-03-11T16:35:43.647 [Information] Device:sensor-th-0055 fanAlert is:False
     2021-03-11T16:35:43.647 [Information] Device:sensor-th-0055 temperatureAlert is:true
     2021-03-11T16:35:43.647 [Information] Device:sensor-th-0055 humidityAlert is:true
     2021-03-11T16:35:43.647 [Information] Device:sensor-th-0055 Temperature is:69.73
     2021-03-11T16:35:43.647 [Information] Device:sensor-th-0055 Humidity is:98.08
     2021-03-11T16:35:43.648 [Information] Executed 'HubToAdtFunction' (Succeeded, Id=9f7a3611-0795-4da7-ac8c-0b380310f4db, Duration=2ms)
     2021-03-11T16:35:43.728 [Error] Service request failed.
     Status: 404 (Not Found)
    
     Content:
     {"error":{"code":"DigitalTwinNotFound","message":"There is no digital twin instance that exists with the ID sensor-th-0055. Please verify that the twin id is valid and ensure that the twin is not deleted. See section on querying the twins http://aka.ms/adtv2query."}}
    
     Headers:
     Strict-Transport-Security: REDACTED
     traceresponse: REDACTED
     Date: Thu, 11 Mar 2021 16:35:43 GMT
     Content-Length: 267
     Content-Type: application/json; charset=utf-8
    
  20. Return to the ADT Explorer instance in the browser and query the graph.

    You should be able to see that the fanAlert, temperatureAlert and humidityAlert properties have been updated.

At this point, the data ingestion from device (in this case a device simulator) into ADT has been demonstrated. The next exercise will demonstrate how telemetry can be streamed to Time Series Insights (TSI).

Exercise 8 - Connect ADT to TSI

In this exercise, you will complete the final part of the proof-of-concept - streaming the device telemetry sent from the Cheese Cave Device sensor-th-0055 via the simulator, through Azure Digital Twins to Time Series Insights.

NOTE: The setup script for this lab created the Azure Storage Account, Time Series Insights Environment and Access Policy that will be used during this exercise.

Routing event data from ADT to TSI is achieved by the following basic flow:

  • ADT publishes notification events to an Event Hub (adt2func)
  • An Azure Function is triggered by events from the adt2func Event Hub, creates a new event for TSI, adds a partition key and published to another Event Hub (func2tsi)
  • TSI subscribes to events published to the func2tsi Event Hub.

In order to implement this flow, the following resources must be created (in addition to ADT and TSI):

  • An Azure Function
  • An Event Hub Namespace
  • Two Event Hubs - one for events from ADT to the Azure Function, another for events from the Azurre Function for TSI.

The Azure function can serve a number of purposes:

  • Map device specific telemetry message formats (property names, data types, etc.) to a single format for TSI. This can provide a consolidated view across different devices as well as insulate the TSI solution from changes to other parts of the solution.
  • Enrich the messages from other sources
  • Add a field to each event for use as the Time Series ID Property within TSI.

Task 1 - Create event hub namespace

An Event Hubs namespace provides DNS integrated network endpoints and a range of access control and network integration management features such as IP filtering, virtual network service endpoint, and Private Link and is the management container for one of multiple Event Hub instances (or topics, in Kafka parlance). The two Event Hubs required for this solution will be created within this namespace.

  1. Login to portal.azure.com using your Azure account credentials.

  2. On the Azure portal menu, click + Create a resource.

  3. In the Search textbox, type Event Hubs and then click the Event Hubs search result.

  4. To create an Event Hub, click Create.

    The Create Namespace page will open.

  5. On the Create Namespace blade, in the Subscription dropdown, ensure that the Azure subscription that you are using for this course is selected.

  6. To the right of Resource group, open the dropdown, and then click rg-az220

  7. In the Namespace name field, enter evhns-az220-training-{your-id}.

    This resource is publically accessible and must have a unique name.

  8. To the right of Location, open the drop-down list and select the same location that you selected for your resource group.

  9. To the right of Pricing tier, open the drop-down list and select Standard.

    TIP: In this exercise, the Basic tier would also work, however in most production scenarios, Standard would be the better choice:

    • Basic
      • 1 Consumer Group
      • 100 Brokered Connections
      • Ingress events - $0.028 per million (at time of writing)
      • Message retention - 1 day
    • Standard
      • 20 Consumer Group
      • 1000 Brokered Connections
      • Ingress events - $0.028 per million (at time of writing)
      • Message retention - 1 day
      • Additional storage - up to 7 days
      • Publisher policies
  10. To the right of Throughput units, leave the selection at 1.

    TIP: The throughput capacity of Event Hubs is controlled by throughput units. Throughput units are pre-purchased units of capacity. A single throughput lets you:

    • Ingress: Up to 1 MB per second or 1000 events per second (whichever comes first).
    • Egress: Up to 2 MB per second or 4096 events per second.
  11. Leave Enable Auto-Inflate unchecked.

    Auto-Inflate automatically scales the number of Throughput Units assigned to your Standard Tier Event Hubs Namespace when your traffic exceeds the capacity of the Throughput Units assigned to it. You can specify a limit to which the Namespace will automatically scale.

  12. To start the validation of the data entered, click Review + create.

  13. Once validation has succeeded, click Create.

    After a few moments the resource will be deployed. Click Go to resource.

This namespace will contain the event hub used to integrate the digital twin telemetry with an Azure function, and an event hub that will take the output of the Azure function and integrate it with Time Series Insights.

Task 2 - Add an event hub for ADT

This task will create an Event Hub that will subscribe to the twin telemetry events and pass them to an Azure Function.

  1. On the Overview page of the evhns-az220-training-{your-id} namespace, click + Event Hub.

  2. On the Create Event Hub page, under Name, enter evh-az220-adt2func

    Note: As the event hub is scoped within a globally unique namespace, the event hub name itself need not be globally unique.

  3. Under Partition Count, leave the value as 1.

    TIP: Partitions are a data organization mechanism that relates to the downstream parallelism required in consuming applications. The number of partitions in an event hub directly relates to the number of concurrent readers you expect to have.

  4. Under Message Retention, leave the value as 1.

    TIP: This is the retention period for events. You can set the retention period between 1 and 7 days.

  5. Under Capture, leave the value set to Off.

    TIP: Azure Event Hubs Capture enables you to automatically deliver the streaming data in Event Hubs to an Azure Blob storage or Azure Data Lake Store account of your choice, with the added flexibility of specifying a time or size interval. Setting up Capture is fast, there are no administrative costs to run it, and it scales automatically with Event Hubs throughput units. Event Hubs Capture is the easiest way to load streaming data into Azure, and enables you to focus on data processing rather than on data capture.

  6. To create the Event Hub, click Create.

    After a moment, the Event Hub is created and Event Hubs namespace Overview is displayed. If necessary, scroll to the bottom of the page and the evh-az220-adt2func Event Hub is listed.

Task 3 - Add an authorization rule to the event hub

Each Event Hubs namespace and each Event Hubs entity (an event hub instance or a Kafka topic) has a shared access authorization policy made up of rules. The policy at the namespace level applies to all entities inside the namespace, irrespective of their individual policy configuration. For each authorization policy rule, you decide on three pieces of information: name, scope, and rights. The name is a unique name in that scope. The scope is the URI of the resource in question. For an Event Hubs namespace, the scope is the fully qualified domain name (FQDN), such as https://evhns-az220-training-{your-id}.servicebus.windows.net/.

The rights provided by the policy rule can be a combination of:

  • Send – Gives the right to send messages to the entity
  • Listen – Gives the right to listen or receive to the entity
  • Manage – Gives the right to manage the topology of the namespace, including creation and deletion of entities

In this task, an authorization rule with Listen and Send permissions will be created.

  1. On the Overview page of the evhns-az220-training-{your-id} namespace, click the evh-az220-adt2func Event Hub.

  2. In the left navigation area, under Settings, click Shared access policies.

    An empty list of policies that are specific to his event hub is shown.

  3. To create a new authorization rule, click + Add.

  4. In the Add SAS Policy pane, under policy name, enter ADTHubPolicy.

  5. In the list of permissions, check only Send and Listen.

  6. Click Create to save the authorization rule.

    After a moment, the pane closes and list of policies refresh.

  7. To retrieve the primary connection string for the authorization rule, click ADTHubPolicy in the list.

    The SAS Policy: ADTHubPolicy pane will open.

  8. Copy the Connection string-primary key value and add it to a new text file named telemetry-function.txt.

  9. Close the SAS Policy: ADTHubPolicy pane.

Task 4 - Add an event hub endpoint to the ADT instance

Now that the Event Hub is created, it must be added as an endpoint that the ADT instance can use as an output to send events.

  1. Navigate to the adt-az229-training-{your-id} instance.

  2. In the left navigation area, under Connect outputs, click Endpoints.

    A list of endpoints, will be displayed.

  3. To add a new endpoint, click + Create an endpoint.

  4. In the Create an endpoint pane, under Name, enter eventhub-endpoint.

  5. Under Endpoint type, select Event Hub.

    The UI updates to include fields to specify the Event Hub details.

  6. In the Subscription dropdown, ensure that the Azure subscription that you intend to use for this course is selected.

  7. In the Event hub namespace dropdown, select evhns-az220-training-{your-id}.

  8. In the Event Hub dropdown, select evh-az220-adt2func.

  9. In the Authorization rule dropdown, select ADTHubPolicy.

    This is the authorization rule that was created earlier.

  10. To create the endpoint, click Save.

    The pane closes and, after a moment, the endpoint list updates to include the new endpoint.

Task 5 - Add a route to send telemetry to the event hub

With the addition of the Event Hub endpoint to the ADT instance, it is now necessary to create a route that sends twin telemetry events to this endpoint.

  1. In the left navigation area, under Connect outputs, click Event routes.

    A list of existing routes are displayed.

  2. To add a new event route, click + Create an event route.

  3. In the Create an event route pane, under Name, enter eventhub-telemetryeventroute.

  4. In the Endpoint dropdown, select eventhub-endpoint.

  5. Under Add a event route filter, leave Advanced editor disabled.

    The advanced editor supports entering a specific filtering expression - for this task, the UI is sufficient.

  6. In the Event types dropdown, select only Telemetry.

    Notice the Filter field displays the generated filter expression.

  7. To create the event route, click Save.

    The pane closes and, after a moment, the event route list updates to include the new route.

Task 6 - Create TSI Event Hub and Policy

This time, the Event Hub and authorization rule will be created using the Azure CLI.

  1. Return to the command prompt and verify the session is still logged in by entering:

     az account list
    

    If prompted to run az login, do so and login.

  2. To create the Event Hub between the Azure Function and TSI, enter the following command:

     az eventhubs eventhub create --name evh-az220-func2tsi --resource-group rg-az220 --namespace-name evhns-az220-training-{your-id}
    

    Remember to replace {your-id}.

  3. To create an authorization rule with listen and send permissions on the new Event Hub, enter the folowing command:

     az eventhubs eventhub authorization-rule create --rights Listen Send --resource-group rg-az220  --eventhub-name evh-az220-func2tsi --name TSIHubPolicy --namespace-name evhns-az220-training-{your-id}
    

    Remember to replace {your-id}.

  4. To retrieve the primary connection string for the authorization rule, enter the following command:

     az eventhubs eventhub authorization-rule keys list --resource-group rg-az220 --eventhub-name evh-az220-func2tsi --name TSIHubPolicy --namespace-name evhns-az220-training-{your-id} --query primaryConnectionString -o tsv
    

    Remember to replace {your-id}.

    The output will be similar to:

     Endpoint=sb://evhns-az220-training-dm030821.servicebus.windows.net/;SharedAccessKeyName=TSIHubPolicy;SharedAccessKey=x4xItgUG6clhGR9pZe/U6JqrNV+drIfu1rlvYHEdk9I=;EntityPath=evh-az220-func2tsi
    
  5. Copy the Connection string-primary key value and add it to the text file named telemetry-function.txt.

    The two connection strings will be required in the next task.

Task 7 - Add the Endpoint addresses as app settings for Azure Function

In order for an Azure Function to connect to an Event Hub, it must have access to the connection string for a policy with the appropriate rights. In this scenario, two Event Hubs are involved - the hub that publishes the event from ADT and the hub that publishes the data transformed by the Azure Function to TSI.

  1. To supply the Event Hub authorization rule connections strings as environments variable, in the Azure portal, navigate to the func-az220-hub2adt-training-{your-id} instance.

  2. In the left navigation area, under Settings, click Configuration.

  3. On the Configuration page, on the Application settings tab, review the current Application settings that are listed.

    The ADT_SERVICE_URL that was added earlier via the CLI should be listed.

  4. To add an environment variable for the adt2func rule connection string, click + New application setting.

  5. On the Add/Edit application setting pane, in the Name field, enter ADT_HUB_CONNECTIONSTRING

  6. In the Value field, enter the authorization rule connection string value that was saved to the telemetry-function.txt file in an earlier task and ends with EntityPath=evh-az220-adt2func.

    The value should be similar to Endpoint=sb://evhns-az220-training-dm030821.servicebus.windows.net/;SharedAccessKeyName=ADTHubPolicy;SharedAccessKey=fHnhXtgjRGpC+rR0LFfntlsMg3Z/vjI2z9yBb9MRDGc=;EntityPath=evh-az220-adt2func.

  7. To close the pane, click OK.

    NOTE: The setting is not yet saved.

  8. To add an environment variable for the func2tsi rule connection string, click + New application setting.

  9. On the Add/Edit application setting pane, in the Name field, enter TSI_HUB_CONNECTIONSTRING

  10. In the Value field, enter the authorization rule connection string value that was saved to the telemetry-function.txt file in an earlier task and ends with EntityPath=evh-az220-func2tsi.

    The value should be similar to Endpoint=sb://evhns-az220-training-dm030821.servicebus.windows.net/;SharedAccessKeyName=TSIHubPolicy;SharedAccessKey=x4xItgUG6clhGR9pZe/U6JqrNV+drIfu1rlvYHEdk9I=;EntityPath=evh-az220-func2tsi

  11. To close the pane, click OK.

    NOTE: The setting is not yet saved.

  12. To save the both of the new settings, click Save and click Continue.

    NOTE: Any change to the application settings will restart the functions.

Task 8 - Review a telemetry Azure Function

In this task, the second Azure function will be reviewed. This function will be responsible for mapping the device telemetry messages to an alternate format for TSI. This approach has the advantage of being able to handle changes to the device telemetry format without changing the TSI solution.

  1. In Visual Studio Code, open the Contoso.AdtFunctions project.

  2. Open the TelemetryFunction.cs file.

  3. Locate the Run method definition and review the code.

     public static class TelemetryFunction
     {
         [FunctionName("TelemetryFunction")]
         public static async Task Run(
             [EventHubTrigger("evh-az220-adt2func", Connection = "ADT_HUB_CONNECTIONSTRING")] EventData[] events,
             [EventHub("evh-az220-func2tsi", Connection = "TSI_HUB_CONNECTIONSTRING")] IAsyncCollector<string> outputEvents,
             ILogger log)
         {
             var exceptions = new List<Exception>();
    
             foreach (EventData eventData in events)
             {
                 try
                 {
                     // main processing code here
                 }
                 catch (Exception e)
                 {
                     // We need to keep processing the rest of the batch - capture this exception and continue.
                     // Also, consider capturing details of the message that failed processing so it can be processed again later.
                     exceptions.Add(e);
                 }
             }
    
             // Once processing of the batch is complete, if any messages in the batch failed processing throw an exception so that there is a record of the failure.
    
             if (exceptions.Count > 1)
                 throw new AggregateException(exceptions);
    
             if (exceptions.Count == 1)
                 throw exceptions.Single();
         }
     }
    

    Take a moment to look at the Run method definition. The events parameter makes use of the EventHubTrigger attribute - the attribute’s constructor takes the name of the event hub, the optional name of the consumer group ($Default is used if omitted), and the name of an app setting that contains the connection string. This configures the function trigger to respond to an event sent to an event hub event stream. As events is defined as an array of EventData, it can be populated with a batch of events.

    TIP To learn more about the EventHubTrigger, review the following resource: Azure Event Hubs trigger for Azure Functions

    The next parameter, outputEvents has the EventHub attribute - the attribute’s constructor takes the name of the event hub and the name of an app setting that contains the connection string. Adding data to the outputEvents variable will publish it to the associated Event Hub.

    As this function is processing a batch of events, a way to handle errors is to create a collection to hold exceptions. The function will then iterate through each event in the batch, catching exceptions and adding them to the collection. Skip[ to the end of the method, and you will see that if there are multiple exceptions, an AggregaeException is created with the collection, if a single exception is generated, then the single exception is thrown.

  4. To review the code that checks to see if the event contains Cheese Cave Device telemetry, locate the // REVIEW check telemetry below here comment and review the following code below it:

     if ((string)eventData.Properties["cloudEvents:type"] == "microsoft.iot.telemetry" &&
         (string)eventData.Properties["cloudEvents:dataschema"] == "dtmi:com:contoso:digital_factory:cheese_factory:cheese_cave_device;1")
     {
         // REVIEW TSI Event creation below here
     }
     else
     {
         log.LogInformation($"Not Cheese Cave Device telemetry");
         await Task.Yield();
     }
    

    This code checks that the current event is telemetry from a Cheese Cave Device ADT twin - if not, logs that it isn’t and then forces the method to complete asynchronously - this can make better use of resources.

    TIP: To learn more about the use of await Task.Yield(); review the following resource:

  5. To review the code that processes the event and creates a message for TSI, locate the // REVIEW TSI Event creation below here comment and review the following code below it:

     // The event is Cheese Cave Device Telemetry
     string messageBody = Encoding.UTF8.GetString(eventData.Body.Array, eventData.Body.Offset, eventData.Body.Count);
     JObject message = (JObject)JsonConvert.DeserializeObject(messageBody);
    
     var tsiUpdate = new Dictionary<string, object>();
     tsiUpdate.Add("$dtId", eventData.Properties["cloudEvents:source"]);
     tsiUpdate.Add("temperature", message["temperature"]);
     tsiUpdate.Add("humidity", message["humidity"]);
    
     var tsiUpdateMessage = JsonConvert.SerializeObject(tsiUpdate);
     log.LogInformation($"TSI event: {tsiUpdateMessage}");
    
     await outputEvents.AddAsync(tsiUpdateMessage);
    

    As the eventData.Body is defined as an ArraySegment, rather than just an array, the portion of the underlying array that contains the messageBody must be extracted, and then deserialized.

    TIP: To learn more about an ArraySegment review the following content:

    A Dictionary is then instantiated to hold the key/value pairs that will make up the properties sent within the TSI event. Notice that the cloudEvents:source property (which contains the fully qualified twin ID - similar to adt-az220-training-dm030821.api.eus.digitaltwins.azure.net/digitaltwins/sensor-th-0055) is assigned to the $dtId key. This key has special meaning as the Time Series Insights environment created during setup is using $dtId as the Time Series ID Property.

    The temperature and humidity values are extracted from the message and added to the TSI update.

    The update is then serialized to JSON and added to the outputEvents which publishes the update to the Event Hub.

    The function is now ready to be published.

Task 9 - Publish the function app to Azure

  1. In the Azure Functions extension for Visual Studio Code, select Deploy to Function App:

    Visual Studio Code deploy to function app

  2. When prompted, make these selections:

    • Select subscription: If prompted, select the subscription you are using for this course.
    • Select Function App in Azure: Select func-az220-hub2adt-training-{your-id}.

    When asked to confirm the deploy, click Deploy.

    The function will then be compiled and, if successful, deployed. This may take a few moments.

  3. Once the deployment has completed, the following prompt will be displayed:

    Visual Studio Code deployment complete - select stream logs

    Click Stream logs and in the confirmation dialog to enable application logging, click Yes.

    The OUTPUT pane will now display the log stream for the deployed function - this will timeout after 2 hours. There will be some status information displayed, however there will not be any diagnostic information from the function itself until it is launched. That will be covered in the next exercise.

    The streaming can be stopped or started at any time by right-clicking the Azure function in Visual Studio Code and select Start Streaming Logs or Stop Streaming Logs:

    Visual Studio Code Azure Function start streaming logs

Task 10 - Configure TSI

  1. In a browser, connect to the Azure Portal and locate the tsi-az220-training-{your-id} resource.

    NOTE: This resource was created by the setup script. If you have not run it, do so now - the script will not impact existing resources.

  2. On the Overview pane, in the Essentials section, locate the Time Series ID Property field and the value - $dtid. This value was specified during the creation of the TSI environment and should match with a field in the event data being streamed to TSI.

    IMPORTANT: The Time Series ID Property value is specified during the creation of the TSI environment and cannot be changed later.

  3. In the left navigation area, under Settings, click Event Sources.

    The list of Event Sources will be displayed - at this point, it should be empty.

  4. To add a new Event Source, click + Add.

  5. On the New event source pane, under Event source name, enter adt-telemetry

  6. Under Source, select Event Hub.

  7. Under Import option, select Use Event Hub from available subscriptions.

  8. Under Subscription ID, select the subscription being used for this course.

  9. Under Event Hub namespace, select evhns-az220-training-{your-id}

  10. Under Event Hub name, select evh-az220-func2tsi.

  11. Under Event Hub policy value, select TSIHubPolicy.

    Notice that the read-only field Event Hub policy key is automatically populated.

  12. Under Event Hub consumer group, select $Default.

    TIP: As there is only one event reader for the evh-az220-func2tsi Event Hub, using the $Default consumer group is fine. If more readers were to be added, then it is recommended that one consumer group per reader is used. Consumer groups are created on the Event Hub.

  13. Under Start time, select All my data.

    Notice there are other options available, such as Beginning now (default), that may be more suitable for a production environment.

  14. Under Event serialization format, notice that the read-only value is JSON.

  15. Under Timestamp property name, leave the value empty.

    TIP: This specifies the name of the event property that should be used as the event timestamp. When not specified, the event enqueue time within the event source will be used as the event timestamp.

  16. To create the Event Source, click Save.

Task 11 - Visualize the telemetry data in Time Series Insights

Now, data should be flowing into your Time Series Insights instance, ready to be analyzed. Follow the steps below to explore the data coming in.

  1. In the browser, return to the Overview pane of the tsi-az220-training-{your-id} resource.

  2. To navigate to the TSI Explorer, click Go to TSI Explorer.

    The TSI Explorer will open in a new tab in the browser.

  3. In the explorer, you will see Azure Digital Twins shown on the left.

    TSI Explorer data

  4. To add telemetry to the graph, click the twin and select EventCount, humidity and temperature.

    Select an appropriate time range, and the displayed data will be similar to:

    TSI Explorer showing time series data

    Note: It may take some time for sufficient data to be displayed.

By default, digital twins are stored as a flat hierarchy in Time Series Insights, however they can be enriched with model information and a multi-level hierarchy for organization. You can write custom logic to automatically provide this information using the model and graph data already stored in Azure Digital Twins.

Congratulations - you are now passing device telemtry data to Time Series Insights.