Module Twin Offline

Question

Module Twin Offline

Daniel Baylon 6

We have implemented an automated deployment for the modules with IoT Edge.

The deployment.template.json is set "properties.desired": {} for that module.

When we try to push the change on the module twin, after awhile, it is clears out.

If the device is offline, and we push the desired properties, device will not be able to retrieve the properties since it clears out.

Is there a way to handle offline mode for the module twin? or before it clears out, device was able to capture the properties?

QuantumCache 20,681 Reputation points Moderator

2022-03-18T18:17:07.583+00:00

Hello @Daniel Baylon

Just checking back, could you please let us know if you need further help in this matter.

Please accept helpful response as 'Answer', which will be helpful to others as well with similar questions, so that we can close this thread.
AshokPeddakotla-MSFT 36,021 Reputation points Moderator

2022-03-21T16:36:33.013+00:00

@Daniel Baylon Wanted to follow up with you to understand whether the below information helped. Please let us know if there are any other queries.
If below suggestions answers your query, do click Accept Answer and Up-Vote for the same. And, if you have any further query do let us know.

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QuantumCache 20,681 Reputation points Moderator

2022-03-18T18:17:07.583+00:00

Hello @Daniel Baylon

Just checking back, could you please let us know if you need further help in this matter.

Please accept helpful response as 'Answer', which will be helpful to others as well with similar questions, so that we can close this thread.
AshokPeddakotla-MSFT 36,021 Reputation points Moderator

2022-03-21T16:36:33.013+00:00

@Daniel Baylon Wanted to follow up with you to understand whether the below information helped. Please let us know if there are any other queries.
If below suggestions answers your query, do click Accept Answer and Up-Vote for the same. And, if you have any further query do let us know.

Answer 1

Sander van de Velde | MVP 37,066 MVP

Hello @Daniel Baylon ,

sending this "properties.desired": {}" inside a deployment manifest will erase all current desired properties (if any available).

Desired properties are readonly from a device perspective. What do you mean with "clears out"? What is happening?

Can you provide some examples of what you experience?

Yes, offline devices work with the last known deployment manifest received. Only when the device reconnects, it gets the new deployment manifest.

There is no 'offline mode' for single modules.

Daniel Baylon 6 Reputation points

2022-03-02T07:17:41.733+00:00

Hello @Sander van de Velde | MVP ,

Thank you for the response.

This is the use case we have.

We have any automated deployment using the deployment manifest for a module which has set to properties.desired : {}.

We understand that it erase the desired properties.

Now, what we want to achieve, if we updated the desired properties of the module twin, properties will not be erased unless the device was able to retrieve that properties.

Example: if we updated the desired properties at 9am, but the device is still offline, desire properties should still be available. Meaning if device becomes online after 11 am,
it still should be able to subscribe the desire properties that has been set.

Thank you so much for assistance.
Sander van de Velde | MVP 37,066 Reputation points MVP

2022-03-02T18:35:35.23+00:00

Hello @Daniel Baylon ,

Azure IoT edge module desired properties in module twins are picked up by their Azure IoT edge module when these are subscribed.

The logic inside the module either listens to the (C#) event or tries to read the properties for the method.

This mechanism is async (the opposite to the DirectMethod which only arrived at the module is the edge device is connected). As long as a device is offline (or even air-gapped) it will never get an update on the deployment manifest (thus desired properties on the module twin).

Note: An IoT Edge device also has a device twin but these desired properties are ignored (you cannot program against it).

This is an older post but still proposing a valid strategy regarding reading the properties.
Somesh Kumar 1 Reputation point

2022-03-04T06:10:13.137+00:00
Hi @Sander van de Velde | MVP ,

We have a similar scenario. We have 20+ devices running IoT Edge modules. They are deployed in remote areas and network is a problem. Here are the two cases we encounter:

Good Case

Push a module twin update for specific device

The device is online

Update success

Trouble Case

Push a module twin update for specific device

The device is offline

Device comes back online after 6hrs

Update is not received

It seems the module twin updates only work when the device is online at the time of the configuration push.

Is there a way to persist module twin updates in the cloud which later get pulled by the device when it comes online?
Sander van de Velde | MVP 37,066 Reputation points MVP

2022-03-04T07:52:00.06+00:00
Hello @Somesh Kumar ,

The device twin is available for the device, always. You can either listen for updates or try to retrieve it forced.

I use this pattern when I start the module (as seen in the post). I force the retrieval of the properties before I attach the callback:

// Execute callback function during Init for Twin desired properties var twin = await ioTHubModuleClient.GetTwinAsync(); await onDesiredPropertiesUpdate(twin.Properties.Desired, ioTHubModuleClient); // Attach callback for Twin desired properties updates await ioTHubModuleClient.SetDesiredPropertyUpdateCallbackAsync(onDesiredPropertiesUpdate, ioTHubModuleClient);

Please try this solution.
Daniel Baylon 6 Reputation points

2022-03-07T08:56:05.527+00:00

Hello @Sander van de Velde | MVP ,

Is the above feature also supported on Java SDK?

If yes, can you provide a sample implementation?

Thanks!
Sander van de Velde | MVP 37,066 Reputation points MVP

2022-03-07T14:40:57.947+00:00

Hello @Daniel Baylon ,

For Azure IoT Edge, a Java SDK is available too:

I'm not able to actually create it on my machine due to the lack of a Java SDK.

This GitHub Issue seems to describe how to do this in Java.

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Module Twin Offline

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