Telemetry Data from IOT hub not pushing to azure function and not reflecting to Digital Twin?

Addanki, Srikar 0

I've been trying to replicate -> https://learn.microsoft.com/en-us/azure/digital-twins/tutorial-end-to-end using my own variables, the telemetry data is pushing to IOT hub but from there on its not getting pushed to the functions eventually my digital twin is not getting updated. I rechecked the variables and naming appropriately, still not getting where the root cause is.

Telemetry data which Im generating:

User's image

Value not getting updated for the device twin, only the static value showing up.

User's image

Matthijs van der Veer 4,376 Reputation points MVP

2023-04-28T07:23:07.1333333+00:00

What steps have you taken to verify that the telemetry reaches the IoT Hub? And how can you tell the Function is not receiving messages? Is there any logging available? Does it work when you follow the tutorial to the letter, without your own variables?
Matthijs van der Veer 4,376 Reputation points MVP

2023-04-28T07:24:09.13+00:00

What steps have you taken to verify that the telemetry reaches the IoT Hub? And how can you tell the Function is not receiving messages? Is there any logging available? Does it work when you follow the tutorial to the letter, without your own variables?
Addanki, Srikar 0 Reputation points

2023-04-28T10:50:30.2833333+00:00

Delivery event failed events found in IOT hub
Sander van de Velde | MVP 31,851 Reputation points MVP

2023-04-28T15:22:36.1533333+00:00

Hello @Addanki, Srikar,

are you sure the messages arrive at the Azure Function because delivery fails?

Can you check the Azure Function logging?

Application Insights give great insights into the execution of Azure Functions. Can you attach Azure Application Insights to your Azure Function?
Addanki, Srikar 0 Reputation points

2023-05-01T05:55:17.14+00:00

Hello Leela,

Yes Ive updated both the fields appropriately, though Ive not used ProcessDTRoutedData.cs file for updating the data through the DT. Ive just used the ProcessHubToDTEvents to update the DT from the IOT hub, which is not happening
LeelaRajeshSayana-MSFT 14,676 Reputation points Microsoft Employee

2023-05-01T14:40:37.1633333+00:00

Hi @Addanki, Srikar Thank you for your response. I have identified one more change to be made in line 44 of ProcessDTRoutedData.cs file. Please refer the below response for the updated answer. Let us know in the comments below if you still face any issues. We would be glad to help you further.

If the answer helped, please do not forget to accept it for the benefit of the other community members.

1 answer

LeelaRajeshSayana-MSFT 14,676 Reputation points Microsoft Employee

2023-04-28T15:51:35.2566667+00:00
Hi @Addanki, Srikar There are couple of places in the Azure function Apps where the patching of Azure Digital Twins is done to the property.

Line 50 of ProcessHubToDTEvents.cs file. Please find the line of the command that comes default with the App

updateTwinData.AppendReplace("/Temperature", temperature.Value<double>());

Line 73 of ProcessDTRoutedData.cs file. Here is the line of code

if (propertyPath.Equals("/Temperature"))

This if condition is specifically looking for a match on Temperature property and only then updates the Digital twin property.

Can you confirm if you have updated the function in both places to replace Temperature with the property you have defined.

Please note that these properties are case sensitive and should be used the same way you have defined in your Model.json file

Inspect the line 44 of ProcessHubToDTEvents.cs file which looks up for the telemetry data pushed from IoTHub and retrieves the property that needs to be patched. The property should be the same as what is defined in line 56 of AzureIoTHub.cs file. Please refer the below line of code

var temperature = deviceMessage["body"]["testpropupdate"];

Line 43 of ProcessHubToDTEvents.cs class reads the Digital Twin ID to which the JSON patch updates need to be applied for. If you follow the step Register the simulated device with IoT Hub in the tutorial as it is, it will create a device with ID thermostat67 which is different from the $dtID of the digital twin. The Azure function in file ProcessHubToDTEvents.cs looks for the same digital twin ID and tries to apply a patch on line 51. Make sure to create a device with ID same as the $dtId of the digital twin.

Once you have function App code modified to reflect the correct property, please make sure to publish the functions again to Azure portal using Azure CLI command az functionapp deployment source config-zip --resource-group <resource-group> --name <name-of-your-function-app> --src "<full-path-to-publish.zip>" so that you have updated code.

After making the above changes, you can see that the property with custom name gets updated as expected on the Azure Digital Twin. Please refer the below images.

Please let us know if you still face issues with the property updates after making the above changes.

If the response helped, please do click Accept Answer and Yes for the answer provided. Doing so would help other community members with similar issue identify the solution. I highly appreciate your contribution to the community.
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Addanki, Srikar 0 Reputation points

2023-05-02T06:52:47.33+00:00

Not sure where the issue is, Ive been updating appropriately, all the files, still facing the same issue.

Line 44 and 50 of ProcessHubToDTEvents.cs

Line 73 of ProcessDTRoutedData.cs

line 56 of AzureIoTHub.cs

How I defined my DT

{ "@id": "dtmi:contosocom:DigitalTwins:ReadingTank;1", "@type": "Interface", "displayName": "ReadingTank interface model", "@context": "dtmi:dtdl:context;2", "contents": [ { "@type": "Property", "name": "Level_of_Material", "schema": "double" }, { "@type": "Property", "name": "State_of_Load", "schema": "string" } ] }

Result from simulator:

Result from DT:

LeelaRajeshSayana-MSFT 14,676 Reputation points Microsoft Employee

2023-05-02T20:35:10.63+00:00

Hi @Addanki, Srikar Thank you for your response. I have used the same Model you have defined and could get the property to update. Here are the steps I have followed.

Modified the BuildingScenario.cs file under the SampleCLientApp project as follows to include the creation of the Model and the digital twin in the InitializeGraph() method

In addition to the earlier mentioned changes, line 43 of ProcessHubToDTEvents.cs class reads the Digital Twin ID to which the JSON patch updates need to be applied for. If you follow the step Register the simulated device with IoT Hub in the tutorial as it is, it will create a device with ID thermostat67 which is different from the $dtID of the digital twin. The Azure function in file ProcessHubToDTEvents.cs looks for the same digital twin ID and tries to apply a patch on line 51.

To resolve this, I have created a device with the same id as Digital Twin and provided the corresponding device connection string in line 25 of AzureIoTHub.cs file.

I could now see the digital twin model receive updates for the property. Please refer the below image

When you want to apply any changes to the Digital Twin model using SampleClientApp, please make sure to delete the existing models from the Digital Twin explorer and run the App again.

Please let us know if you still face any issues. We would be glad to connect with offline and investigate this further to resolve this.

Addanki, Srikar 0 Reputation points

2023-05-03T10:39:42.08+00:00

Hi Rajesh, thanks for the response.

I've been creating a new device based on the name ReadingTank itself whenever Im creating as mentioned below and using the same connection string in line 25 of AzureIoTHub.cs file. This is has been the case while following the tutorial as well, where I was replacing the thermostat67 to ReadingTank

and when I try to observe the properties, getting a static value

Heres how Ive defined my files:

ProcesshubtoDTEvents.cs -> Line 43,44,50

ProcessDTRoutedData.cs -> Line 73

AzureIOTHub.cs -> line 56

Please let me know if we can connect offline

LeelaRajeshSayana-MSFT 14,676 Reputation points Microsoft Employee

2023-05-03T23:50:35.4633333+00:00

Hi @Addanki, Srikar For a deeper investigation and immediate assistance on this issue, please file a support request @ https://aka.ms/azsupt? If you do not have access to a support plan, could you please send an email to azcommunity@microsoft.com with the below details, so that we can work closely on this matter.

Thread URL: Link to this thread.
Azure Subscription ID:
Email Subject : Attn Leela

Addanki, Srikar 0 Reputation points

2023-05-05T12:21:04.9333333+00:00

Hi Rajesh,

Thanks a lot for connecting and sorting out the issue. Not sure how but when I was trying from my end with the same code, static value was populating. This caused a blocker for a week, which might be due to an issue at event hub as suggested by one of your colleague. Will see if I can reproduce this issue but thanks a lot for the support provided.

LeelaRajeshSayana-MSFT 14,676 Reputation points Microsoft Employee

2023-05-05T14:27:12.44+00:00

Hi @Addanki, Srikar Glad to connect with you and answer your questions. We will work on testing this tutorial further and see if we can encounter the same behavior as you initially noticed.

If the response helped, please do click Accept Answer and Yes. Doing so would help other community members with similar issue identify the solution. I highly appreciate your contribution to the community.
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