Using the Gateway Object for Child Devices

[AbdIssa98]

Question

Hello,

I have checked 1718 and although it is in the same direction as my question, it does not answer it, therefore I am opening this issue here.

Context:

I am using the gateway object to publish child devices that use my main lwm2m device as a gateway. my implementation is based on article.

In my implementation, I am using the same logic in branch so that I save the child and parent device relations in additional registration attributes.

I am also using send requests to handle incoming measurements from the gateway and its child devices. I made changes to the HandlePOST() function in SendResource.java class and TimeStampedLwM2MNode class to consider prefixes to deduce if the send request comes from the parent or child node.

Since the child devices do not have their own lwm2mIdentity and IP Address, I have changed the redis and InMemory registration stores to only save those if the rootpath of the registration does not have a prefix i.e. the gateway/parent. this avoids conflicts in registration and in ClientProfileProvider.

implementation details: compare branch.

Core question:

I want to eventually create a pull request for these changes, but my main question is: using additional registration attributes does not sit right with me, and so I would want to add attributes to the Registration.java class for the names of child devices and name of gateway/parent. would such a change be meaningful or should I make the change elsewhere?

TL;DR:

• Extending the gateway object to support child devices.

• Using prefixes in send requests and registrations to distinguish parent vs. child.

• Considering a PR: Should gateway/child info live in Registration.java or somewhere else?

Thanks in advance for your feedback

[sbernard31]

Hi,

I started to think a bit more about integrated Gateway feature in Leshan (see #1237 (comment))

By the way could you answer to that questions (#1237 (comment))

---

I understand that you used the obj25_alt but looking at #1237 (comment) it seems that maybe obj25_alt2 could be a better approach. Any reason about that choice ?

(I'm not sure but alt2 should probably works with send feature 🤔)
(Also note that not only gatewayDevice can use rootpath. In other word : rootpath doesn't imply gatewayDevice)

---

Also note that obj25_alt and obj25_alt2 was created with the idea in mind to not be integrated in Leshan directly.
This was about exploring solution for user to be able to use Gateway Feature with current Leshan API.
So main goal was to be less code impacting as possible.

If now we finally decide to support Gateway directly in Leshan then main goal is now to have a good/clear design and API AND so it's totally OK to change code more deeply. (API break could be considered as well)
Just to say that's not sure obj25_alt or obj25_alt2 are the best approach in that case.

---

Could I know how you're testing your code for now ?

[AbdIssa98]

Hi,

I started to think a bit more about integrated Gateway feature in Leshan (see #1237 (comment))

By the way could you answer to that questions (#1237 (comment))

I understand that you used the obj25_alt but looking at #1237 (comment) it seems that maybe obj25_alt2 could be a better approach. Any reason about that choice ?

(I'm not sure but alt2 should probably works with send feature 🤔) (Also note that not only gatewayDevice can use rootpath. In other word : rootpath doesn't imply gatewayDevice)

Also note that obj25_alt and obj25_alt2 was created with the idea in mind to not be integrated in Leshan directly. This was about exploring solution for user to be able to use Gateway Feature with current Leshan API. So main goal was to be less code impacting as possible.

If now we finally decide to support Gateway directly in Leshan then main goal is now to have a good/clear design and API AND so it's totally OK to change code more deeply. (API break could be considered as well) Just to say that's not sure obj25_alt or obj25_alt2 are the best approach in that case.

Could I know how you're testing your code for now ?

When I first started implementing the gateway object I was not intending to use the send features and so obj25_alt was sufficient (I did not check obj25_alt2 and did not know it had support for send features)

I am testing my code using a hardware device that uses lwm2m zephyr library. the device was made in such a way that in send requests the rootpath will be the same as the prefix published in the registration of the child device, and that the parent would have "/" as its rootpath at all times. I based my implementation on these points

[sbernard31]

I did not check obj25_alt2 and did not know it had support for send features

I'm not sure it work. I see #1237 (comment) which let me think that it maybe works.... but thinking a bit more about it, I think it could work only if you don't mix data from several child devices. So this part of the code(and API) should be largely modify to support that use case.