I have a scenario where data comes from a module and i send it to IOT Hub in another module. When internet is not working the messages are stored in a queue by a in built azure function. I want to store these data locally so that if my system crashes these data does not vanish. When there is no internet the interpreter is not coming out of the function send_message_to_output() since its waiting for a Ack from the cloud , which won't happen until the network is back. Is there any function I can use to store these data locally even when there is no internet or is there any work around for this?

Hello @ambharesh venkatraman , as mentioned above, offline support is already built-in into Azure IoT Edge. Messages are persisted on disk until the internet connection comes back. The location the messages are stored is adjustable as seen in here . This is also part of ruggedizing your edge device. Give both the edgeHub and edgeAgent access to a folder using an Environment variable and Container Create options. In Linux, this an example for both modules: { "HostConfig": { "Binds": [ "/etc/iotedge/storage/:/iotedge/storage/" ] } } (merge this with the already existing edgeHub container create options) and the environment variable: storageFolder = /iotedge/storage/ Make sure the folder "etc/iotedge/storage" exists on disk and has enough access rights. There are extra capabilities like priority messages and TTL on the edge routing configuration also.

Iot Edge offline capabilities

Accepted answer

Sander van de Velde | MVP 32,641 Reputation points MVP

2021-03-24T19:02:30.507+00:00
Hello @ambharesh venkatraman ,

as mentioned above, offline support is already built-in into Azure IoT Edge.

Messages are persisted on disk until the internet connection comes back.

The location the messages are stored is adjustable as seen in here.

This is also part of ruggedizing your edge device.

Give both the edgeHub and edgeAgent access to a folder using an Environment variable and Container Create options.

In Linux, this an example for both modules:

{ "HostConfig": { "Binds": [ "/etc/iotedge/storage/:/iotedge/storage/" ] } }

(merge this with the already existing edgeHub container create options)

and the environment variable: storageFolder = /iotedge/storage/

Make sure the folder "etc/iotedge/storage" exists on disk and has enough access rights.

There are extra capabilities like priority messages and TTL on the edge routing configuration also.
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1 person found this answer helpful.
ambharesh venkatraman 61 Reputation points

2021-03-25T02:47:59.88+00:00

Thank you so much for the help.

ambharesh venkatraman 61 Reputation points

2021-04-14T14:29:19+00:00

Hi ,
The local storage is saving it as binary files. is there any way that we can store them in a readable format?

Thanks,
Ambharesh

Sander van de Velde | MVP 32,641 Reputation points MVP

2021-04-14T16:23:45.303+00:00

Hello @ambharesh venkatraman ,

I check the related documentation, I do not see a property for managing the format.

You can give feedback on the module and even submit a feature proposal here (Share the proposal link so we can upvote).

ambharesh venkatraman 61 Reputation points

2021-04-14T16:53:34.427+00:00

Hi @Sander van de Velde | MVP ,

Thanks for the response. I have posted a feedback and I'm sharing the link.

https://feedback.azure.com/forums/907045-azure-iot-edge/suggestions/43164843-storing-the-offline-capabilities-data-in-user-read

Sander van de Velde | MVP 32,641 Reputation points MVP

2021-04-14T18:09:42.153+00:00

Hello @ambharesh venkatraman ,

Sorry for the inconvenience. I misinterpreted your newest question.

The offline capabilities are a perfect way to persist messages, waiting to be sent to the cloud in case of a temporary offline situation.

The messages are then in control of the Azure IoT edge routing so these are secured and are not available from the outside.

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Sander van de Velde | MVP 32,641 Reputation points MVP

2021-04-14T18:09:53.597+00:00

It seems you want to persist some state?

If you want to persist some logic in any module that is remembered once a module is restarted, you can connect to that same database or blob storage (this means you have to code for that connection).

A sneaky workaround is making use of the Reported properties... These can both be written and read by a module. Warning: updating a reported property means sending a module twin update to the cloud. So this will be counted as D2C communication.

Finally, you could make use of local storage inside your own module. Just save some state on disk.

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