Re: [hono-dev] Command & Control response buffering

[Marc Pellmann <pellmann@xxxxxxxxx>]

Hi Avgustin,

as written on the concept page the Command and Control API defines commands that follow a request-response pattern and expect an immediate confirmation of their result. But we do not define that this need to be the result of the execution of the command. The device could also immediately acknowledge receipt as part of the request-response-pattern. 

If the use case needs a later response (which then also needs the guarantee of delivery) the device is able to do such with a normal event. In such a case I would also assume that the application has some kind of persistence of the expected execution result correlation because it could not be sure, that it is the same instance who gets the response (this would also be the case if the response would arrive hours or days later on the direct response link - which not an intended case).

Maybe it makes sense to define specific properties and e.g. content-type for such command-response events in later versions.

Best regards,

Marc

On Wed, Jun 20, 2018 at 11:53 AM Marinov Avgustin (INST/ECS8) <Avgustin.Marinov@xxxxxxxxxxxx> wrote:

Hi all,

 

as far as I understand, currently, the responses (replies) for the commands will be lost if there is no registered consumer. This could be a problem in some cases. For instance if the command execution on the device side takes too long – e.g. hours.

In that case when the response is returned the backend application may be down and the result of the execution could be lost. I thing that it would be better to have buffering of the command responses on in hono in order to provide guaranties that the response of the commands will reach the backend application. After all, such guaranties are available for the events. And the command results are maybe event more important then events.

 

What do you thing?

 

Поздрави / Best regards,

Avgustin Marinov

Engineering Cloud Services Device Manager
(INST/ECS8)
Bosch Software Innovations EOOD | 47B Tsarigradsko Shose | Sofia 1124 | BULGARIA | www.bosch-si.com
Tel. +359 2 9055801 | Mobile +359 889 464664 | Fax +359 2 9532617 | Avgustin.Marinov@xxxxxxxxxxxx

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