How to send data from UDF to Cosmos DB in Azure Digital Twin?

Question

Setup till now: I have created spaces. At the top level I have the IOT hub resource. In two of spaces, I have attached devices to it along with the sensors. I have created a Matcher for the Temperature sensor along with the UDF that is similar to the documentation . I have also assigned permissions to UDF. To send data to IOT hub, I have also fetched the device connection string for the dotnet sample

List of issues I am facing:

1. When I try to run the dotnet sample , I can see that it is able to reach the UDF(checked it via debugging), but in the UDF, it is not able to access the telemetry variable as given in documentation . The error it shows is :

Unexpected exception occurred while processing user-defined function. Please contact support and provide the correlation ID for the request.

2. I have created an endpoint to send Raw Telemetry to Event Hub. But I want to send the processed data from UDF to cosmos db. Is it possible? If yes then how?

Answer 1

Thanks for the question and reaching out...for #2 you could do this by doing a notify method in your UDF. You can setup egress to other endpoints such as Event Hub, Event Grid or Service Bus via the endpoint dispatcher. You would setup endpoint via the /endpoint API and then in your UDF you could specify what you want to send out and which changes. For details on the events and endpoints you can see here: https://docs.microsoft.com/en-us/azure/digital-twins/how-to-egress-endpoints

Here's also here is a link to learn more about this connecting Digital Twins over to Logic Apps: https://docs.microsoft.com/en-us/azure/digital-twins/tutorial-facilities-events which would have a similar pattern to sending data over to Cosmos DB.

As for the first one I am not sure if you are still seeing this. Which region? Do you have a correlation ID that you can pass along? Also if you turn on logs and look in Azure Monitor are there details there?