Logging Custom Messages/Exception from IoT Edge Custom module in C# to IoT Hub

Satyam Chauhan 512

Hi,

We have created a C# custom module, which sends messages to IoT Hub with SendEventAsync Method. There may be a case when some problem occurs in the module, I wanted to send some logs to IoT hub so that I can monitor if the module is working fine or some problem has occurred. I want to send both success and failure response.

Please let me know any solution how can I log custom logs in C# modules and see the same from Cloud/Portal.
Thanks,
Satyam

QuantumCache 20,031 Reputation points

2022-09-22T18:07:08.35+00:00

Hello @Satyam Chauhan If the response is helpful, please click "Accept Answer" and upvote it.
So that we close this thread and is useful to the community.
AshokPeddakotla-MSFT 27,976 Reputation points

2022-10-06T04:55:25.23+00:00

@Satyam Chauhan 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.

1 answer

Sander van de Velde 29,281 Reputation points MVP

2022-09-20T17:51:12.983+00:00

Hello @Satyam Chauhan ,

the simplest way is sending separate messages based on exceptions or error flow inside the modules.

These messages are preferably sent over a separate output. These 'error' outputs are routed on the edge to $upstream.

Notice, these messages have probably a different body format compared to the regular telemetry. I suggest adding an application property telling the body contains an exception/success/failure.

When these 'error' messages arrive in the IoT Hub, you can route them to a custom/separate endpoint, eg. an Event Hub.

From there you can respond in real-time if these 'error' messages arrive.

It's a good idea to store these message in a blob storage or Azure Data Explorer for historical purposes.
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2 people found this answer helpful.
Satyam Chauhan 512 Reputation points

2022-09-21T10:41:40.667+00:00

Hi @Sander van de Velde ,

Thank you for your answer.

Is this the ideal way to send exceptions/error from edge module to iot hub, like in our case we may want to create an alert rule if the module is not function properly due to any reason. It would be nice if you provide any example related to this.

Also, is there any other way of achieving this?

Sander van de Velde 29,281 Reputation points MVP

2022-09-21T14:25:58.577+00:00

Hello @Satyam Chauhan ,

there is no standard way of logging exceptions/errors/warnings/confirmations.

You have to build it yourself using eg. traditional try/catch/finally logic and sending some structured message to a different endpoint so you are flexible with routing.

If you encounter a fatal error, you could decide to NOT catch it and let the module crash so it will be restarted by the Moby engine. This is how daemon processes sometimes recover...

Next to this logging route, also check out the Metrics collector of Azure IoT Edge. It's easy to setup. This gives good insight into the health of both modules and IoT Hub. It's possible to integrate this with alerts in Azure Log Analytics.

I have not used it myself but perhaps Custom Metrics could help you also.

Satyam Chauhan 512 Reputation points

2022-10-14T04:26:13.36+00:00

Hello @Sander van de Velde ,

Thank you for your input.

I see in the troubleshoot section of the modules there are logs which I require.
Is there any way we can use the logs visible in troubleshoot section of the modules in IoT hub portal. Like, is there a way way we can have these logs in log analytics?

Thank you.

Sander van de Velde 29,281 Reputation points MVP

2022-10-14T06:49:51.77+00:00

Hello @Satyam Chauhan ,

you could send each line you log as a separate message to the cloud and put it into log analytics.

But this seems an expensive solution without much value.

But you can get access to the module logs using already available Direct Methods on the edgeAgent.

if you go to the Azure Portal and select the details page of a module, check out the 'Troubleshoot' page where you can select any module and see the logging of that module while the edge device is online.

This UI is based on the same direct methods functionality.

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If the response helped, do "Accept Answer". If it doesn't work, please let us know the progress. By doing so, all community members who have a similar issue will benefit. Your contribution is highly appreciated.

Satyam Chauhan 512 Reputation points

2022-10-18T08:04:17.41+00:00

Hello @Sander van de Velde ,

I have one more doubt with direct method invoking. Do we have to manually invoke the direct methods in order to get the logs and upload them to storage account.

Thanks.

Sander van de Velde 29,281 Reputation points MVP

2022-10-18T09:57:57.127+00:00

Hello

The Azure IoT hub offers an API to execute Direct Methods on IoT Edge modules.

See also this documentation.

Satyam Chauhan 512 Reputation points

2022-10-18T12:38:14.243+00:00

Thanks @Sander van de Velde ,

Just wanted to check for how long the logs are retained in IoT hub, and can we filer the logs based on log level while calling the direct method.

Thanks for helping

Sander van de Velde 29,281 Reputation points MVP

2022-10-18T21:38:24.297+00:00

Hello @Satyam Chauhan ,

you are making a 'Direct Method' call.

Here, 'Direct' means you connect directly to the connected device. This call is blocking. You either get a response once the device is ready with executing the method call or an error occurs or a time-out occurs.

There is no logging stored in the IoT Hub.

The logging is read live by the edgeAgent module from the hard disk of your edge device.
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