Exam AZ-220 topic 4 question 4 discussion

Actual exam question from Microsoft's AZ-220

Question #: 4
Topic #: 4

You have 1,000 devices that connect to a standard tier Azure IoT hub.
All the devices are commissioned and send telemetry events to the built-in IoT Hub endpoint.
You configure message enrichment on the events endpoint and set the enrichment value to $twin.tags.ipV4.
When you inspect messages on the events endpoint, you discover that all the messages are stamped with a string of "$twin.tags.ipV4".
What are two possible causes of the issue? Each correct answer presents a complete solution.
NOTE: Each correct selection is worth one point.

A. The ipV4 tag is a restricted twin property that is unavailable for message enrichment.
B. A standard tier IoT hub does not support device twin properties in message enrichments.
C. The device sending the message has no device twin.
D. Message enrichment cannot be added to messages going to a built-in endpoint.
E. The device twin path used for the value of the enrichment does not exist.
F. The device twin property value used for message enrichment is set to "$twin.tags.ipV4".

Show Suggested Answer

Suggested Answer: CE 🗳️
In some cases, if you are applying an enrichment with a value set to a tag or property in the device twin, the value will be stamped as a string value. For example, if an enrichment value is set to $twin.tags.field, the messages will be stamped with the string "$twin.tags.field" rather than the value of that field from the twin. This happens in the following cases:
✑ (C) Your IoT Hub is in the standard tier, but the device sending the message has no device twin.
✑ (E) Your IoT Hub is in the standard tier, but the device twin path used for the value of the enrichment does not exist. For example, if the enrichment value is set to $twin.tags.location, and the device twin does not have a location property under tags, the message is stamped with the string "$twin.tags.location".
✑ Your IoT Hub is in the basic tier. Basic tier IoT hubs do not support device twins.
Reference:
https://docs.microsoft.com/en-us/azure/iot-hub/iot-hub-message-enrichments-overview

by sanjayqz at Nov. 25, 2020, 2:06 p.m.

Comments

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ADC88

Highly Voted 4 years, 2 months ago

Given answer is correct as confirmed by the doc: https://docs.microsoft.com/en-us/azure/iot-hub/iot-hub-message-enrichments-overview#limitations

upvoted 9 times

exam67

4 years ago

that's correct, but I don't understand how can a device have no twin. Is there a way to remove the twin document from the device?

upvoted 2 times

d0bermannn

3 years, 6 months ago

yes,it is possible to delete twin: Developer way=https://docs.microsoft.com/en-us/azure/digital-twins/how-to-manage-twin DevOps way=https://docs.microsoft.com/en-us/powershell/module/az.digitaltwins/remove-azdigitaltwinsinstance?view=azps-7.0.0

upvoted 1 times

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trickerk

3 years, 10 months ago

Yes... given answer is correct according the link you posted.

upvoted 2 times

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frederik_1

Highly Voted 4 years, 6 months ago

I'd think that a device always has a device twin. Therefore I'd think that the correct answers are E & F.

upvoted 7 times

jodol89125

4 years, 4 months ago

Device twin not available in basic tier: https://azure.microsoft.com/en-gb/pricing/details/iot-hub/

upvoted 1 times

BoomJosh

4 years, 3 months ago

Question clearly says that its a standard tier IoT Hub!!!

upvoted 2 times

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trickerk

3 years, 10 months ago

Wrong. Given answer is correct according the link: https://docs.microsoft.com/en-us/azure/iot-hub/iot-hub-message-enrichments-overview#limitations CE

upvoted 3 times

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j_c_000

Most Recent 2 years, 1 month ago

Note that as of Apr 21, 2022, it is no longer correct that this can happen because the device has no twin. See the docs change at: https://github.com/MicrosoftDocs/azure-docs/commit/531a67df2bcebc8d448bae10e46f2631ff8fe888 Device twins are only deleted when the device identity is removed See: https://learn.microsoft.com/en-us/azure/iot-hub/iot-hub-devguide-device-twins#device-twins Note that the comment here about deleting twins refers to DIGITAL twin, which is something different than DEVICE twin.

upvoted 1 times

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