I'm developing a web application in .NET Core 3 and I'm using the Microsoft.Azure.Devices.RegistryManager to access an Azure Iot hub.
When I call registryManager.UpdateTwinAsync(), I have to send in the "etag". And sometimes the etag changes and I get errors stating that there is an etag mismatch.
I basically don't understand what the etag's purpose is and how I can update device twins in a safe manner. Anyone?
I tried catching those exceptions and fetching the etag from the device twin and retrying up to 15 times in a row with 2 seconds wait in between and that helps, but this error pops up every now and then. I would think that applying the device id would be enough to update a device twin but apparently not
Please help!
So in a simple terms we can say that ETag - Entity tag will keep changing when ever we see there is a change in device status or any other updates.
A string representing a weak ETag for the device identity, as per RFC7232 Section 2.3 Etag.
An entity-tag is an opaque validator for
differentiating between multiple representations of the same
resource, regardless of whether those multiple representations are
due to resource state changes over time
For example: Enable and Disable an IoT Device and check the 'Get device Info' from Visual Studio Code (Azure IoT Hub Extension)
Step 1) I have an initial IoT device with status Enabled and I can see an Etag value.
Step 2) When I disabled the device on IoT Hub portal, and then did second query 'Get Device Info' call, I see a different value on ETag.
Step 3) Now when I queried for the second time (like after 5 mins interval), I see the Etag value remains same for the same disabled state of device.
**For more info please visit Device identity properties, Module identity properties
**Please let us know if you need more help on this!
My understanding is that the ETag is used to ensure consistency on the device twin when you're updating it. It's read-only so you would get it from your device twin and pass it back to UpdateTwinAsync() with your changes. Link
I'm not sure what you mean when you say the ETag is changing - can you provide some code of what you are doing (or clarify when the ETag is changing)?
I created a video on YouTube that demos how to read/write Azure Device Twins, so feel free to check it out, hopefully it helps you! Link
For some additional information about how device twins use optimistic concurrency to ensure consistency when there are potentially multiple updates from different users, see Understand and use device twins in IoT Hub > Optimistic concurrency on Microsoft Docs.
Related
IoT Hub has the ability to enrich messages prior to being sent to an endpoint. It appears that the device twin's information can be added, but I don't see anything about the module twins online.
The use case here would be we will likely version a module data model contained within the messages at some point in the future. We would like to enrich the messages sent to endpoints with metadata about the state of the module it came from.
Another option that doesn't seem to exist is the ability to update device twin properties on deployment. Were this doable, then potentially we could update a modules version information at the device twin level.
Is this the wrong way to think about twins? Aka were such functionality even available, would the enrichment take the point in time twin reported value? Could there even be any guarantee that the twin has the correct reported value at the time the module sent the message? It that is the case, is the only real reliable way to send metadata about a module's message is within the message itself?
If you send an event from within a module using a module client, the keyword $twin in the message enrichment will refer to the module twin.
I have a free tier subscription to Azure IoT hub with only two edge devices connected to it, one of them mostly off. Yesterday, it looks like my hub recorded a slew of messages--within 45 minutes (5 to 5:45 pm PST), 25K messages were recorded by the hub. A few related issues.
I'm not sure what these messages were. I'll add message storage for the future, but wondering if there's a way to debug this.
Ever since then, I haven't been able to use the IoT hub. I get a "message count exceeded" error. That made sense till around 5 pm PST today (same day UTC), but not sure why it is still blockign me after that.
I tried to change my F1 to a basic tier to basic, but that wasn't allowed because I am apparently "not allowed to downgrade"
Any help with any of these?
1.I'm not sure what these messages were. I'll add message storage for the future, but wondering if there's a way to debug this.
IoT Hub operations monitoring enables you to monitor the status of operations on your IoT hub in real time. You can use it to monitor Device identity operations,Device telemetry,Cloud-to-device messages,Connections,File uploads and Message routing.
2.Ever since then, I haven't been able to use the IoT hub. I get a "message count exceeded" error. That made sense till around 5 pm PST
today (same day UTC), but not sure why it is still blockign me after
that.
IoT Hub Free edition enables you to transmit up to a total of 8,000 messages per day, and register up to 500 device identities. The device identity limit is only present for the Free Edition.
3.I tried to change my F1 to a basic tier to basic, but that wasn't allowed because I am apparently "not allowed to downgrade".
You cannot switch from Free to one of the paid editions. The free edition is meant to test out proof-of-concept solutions only.
Confirming the earlier answer, the only solution is to delete the old hub and create a new free one, which is simple enough.
I still haven't figured out what those specific error messages were, but I do notice that when there are errors such as CA certificate auth failures, lots of messages get sent up. I'm still working with MSFT support on the CA certificate signing issues, but this one is a side effect.
For future reference, look at yoru hub's metrics, and note that (i) quote gets reset midnight UTC, but (ii) net violations do not.
We have around 9000 devices in field.
This devices are at groups of 1-100 at customers on prem.
The devices are not capable of azure-iot-sdk integration.
The devices have a webservice API.
The devices should appear as first-class devices in azure.
We like the iot edge module provisiong feature.
We want to evaluate if modules could gather data from the devices and send them to IoTHub for further processing.
We found this feature overview of IoTEdge: https://learn.microsoft.com/de-de/azure/iot-edge/iot-edge-as-gateway
Pattern Transparent and Protocol translation are out of scope due to above facts. Pattern Identity translation seems to fit.
We want a 1 to 1 relationship between module and real device.
Therefor we assume the following POC with the hope of clarification and best practise:
we implement a iot edge module (azure-iot-sdk-java)
we open module connection to iotedge and suscribe to desired properties
the module identity gets as desired property the ip of the real device and the azure device identitiy connection string.
we open device connection to iotedge by adding GatewayHostName to the device connection string as described here https://learn.microsoft.com/de-de/azure/iot-edge/iot-edge-as-gateway
we request data from the real device and send them via azure device identity.
This somewho mixes up two patterns and seems kind of odd to us.
Can you point out best practises and risks with this approach?
Yes, I agree with that Pattern Identity translation could fit your scenario.
There are three patterns for using an IoT Edge device as a gateway: transparent, protocol translation, and identity translation, you can refer to this link to get more introduction about these three pattern.
Since we plan to use MTP (Media Transfer Protocol) for your next device, we evaluate the use of MTP as replacement for the current (unstable) USB drivers in the current released device.
The limitation on this device is, that its processor (Strong Arm) supports only up to 3 EndPoints:
"Serial port 0 is a universal serial bus device controller (UDC) that supports three endpoints and can operate half-duplex at a baud rate of 12 Mbps (slave only, not a host or hub controller)."
But according to the specification, MTP needs at least 4 endpoints (from the PTP spec):
"The device shall contain at least four endpoints: default, Data-In, Data-Out, and an Interrupt endpoint."
Now the question: Can we just skip the interrupt endpoint on the device? I know that it violates the specification - but what happens if we do?
From our current evaluation software I can see the following scenarios:
The 'space available' is not updated - the user will see that there is 100Mb of free memory, but placing a 1Mb file gives the error "Not Enough Memory"
Non-host driven actions are not visible on the host (so when on the device files are deleted, created or moved, the connected host does not know about it)
If we can live with it, is it advisable to implement it this way?
UPDATE: Damn... when I tested it last time, I ve just removed the code for interrupt-EP data transmission. Now I also removed the endpoint definition (I do not create the endpoint anymore) and from this point the MTP connection couldn't be established any more :(
It seems that the windows driver (wpd) requires the interrupt endpoint - even if it's not used. Bad luck...
Has anyone an idea, whether and how to get MTP working with 3 endpoints?
Finally I got an answer from Microsoft:
The 3-endpoints setup is not supported.
The interrupt endpoint is required so that the driver can receive MTP events from the device. These events are a notification mechanism that the driver relies on to relay events to applications (e.g. when an object is created, updated, or removed).
If your device does nothing with the endpoint (i.e. send no events), applications such as Explorer will not behave correctly whenever objects on your device are changed.
So we buried our plans... :(
I have a requirment to use Android C2DM functionality.
However, the restriction is that there should be no data that goes outside organization network.
Does the server side implementation send data to Google servers?
Is there an option to implement C2DM service within a closed network, where the data is not sent to Google servers?
Thanks,
RR
The purpose of C2DM is that you "Notify" the device that new data is available, and then your application is starting a sync (or something else, eg showing a message).
In general you don't submit the data (sometimes called payload) using C2DM. It is limited to 1024 chars only.
This way no "company" data is sent to Google.