Iotedge: [edgeHub] Support for incoming cloud to module messages in edgeHub

[emilm]

Ref issue https://github.com/Azure/azure-iot-sdk-csharp/issues/1370
@timtay-microsoft responded that edgeHub does not support this.

My usecase is that someone interacts with my device / module, and it needs to request the server to respond to the query from the user interacting with the device. The ideal thing would be a Direct Method to cloud from device/module, but that's not there. So in order to respond, the server has to
a) respond with C2D (cloud to _module_ really) so my edge module can act accordingly
b) respond with Direct Method to module (not optimal, but works)
c) remove GATEWAY_HOSTNAME or something to bypass edgeHub and connect directly (what's the right way to do this?)

I think this important that you have a coherent solution for 2 way messaging, so you don't have to respond with a Direct Method to the Module which will create an unnecessary response. A request-response with DM would be device -> cloud - request->response->"request"

Thanks! :)

[dmolokanov]

@veyalla Could you comment on this, please?

[veyalla]

@emilm are you asking for this feature?

[emilm]

@emilm are you asking for this feature?

Correct! Most of it seems to be in place. The only missing piece seems to be edgeHub. It already works for Direct Methods to a module.

I see that the FR has been there since 2018 and I assumed it was dead. :)

[veyalla]

An update was provided in Nov 2019 (see the comments). Still the same status, unfortunately. It is not in our near-term roadmap.

Let's continue to use the feedback site to track.

[emilm]

OK. What do you recommend me to do in this case?

a) Use direct methods as a response mechanism (works today)
b) set up the module to connect directly to IoT hub and not via edgeHub (how is this done?)
c) ???

Thanks.

[veyalla]

a) is the recommended pattern with IoT Edge today.