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Re: [leshan-dev] cancelling a queued request
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Hi Kai,
We had discussed about TTL before thinking about cancelling a request. Even though it looks simple at first, it adds complexity depending upon how it can be achieved. IMO, TTL requirements differs from one application to another.
Say,
- one might require TTL to be an absolute time. As many systems could be involved like message broker, Northbound API, Leshan etc., it would make sense to use an absolute time. But it requires all systems to be in time synced.
- TTL can be a relative time. For ex. Relative to when Leshan has received the message.
- TTL doesn't guarantee that on expiry the message is not sent to a LWM2M client. i.e:- It could have been valid at the time of delivery but before the response has arrived, TTL has expired.
- TTL can also be realized based on retry count. For ex. After 10 retries the message is removed automatically.
Considering the complexity of TTL, we thought of having cancelling a request as the first step and build TTL based on that if really necessary or one could also leave the entire TTL handing to the application layer and let it use this cancel request method.
Also such a cancel request is not necessarily only for TTL's use case but can also be used to rollback any message queued previously.
Regards,
Bala
-----Ursprüngliche Nachricht-----
Von: leshan-dev-bounces@xxxxxxxxxxx [mailto:leshan-dev-bounces@xxxxxxxxxxx] Im Auftrag von Hudalla Kai (INST/ESY1)
Gesendet: Freitag, 22. Juli 2016 17:45
An: leshan-dev@xxxxxxxxxxx
Betreff: Re: [leshan-dev] cancelling a queued request
Is there a particular reason why you want to be able to explicitly cancel a request instead of e.g. just being able to set a TTL on the request so that it "automatically" is removed from the queue if it expires?
--
Mit freundlichen Grüßen / Best regards
Kai Hudalla
Chief Software Architect
Bosch Software Innovations GmbH
Schöneberger Ufer 89-91
10785 Berlin
GERMANY
www.bosch-si.com
Registered office: Berlin, Register court: Amtsgericht Charlottenburg, HRB 148411 B;
Executives: Dr.-Ing. Rainer Kallenbach, Michael Hahn
On Fr, 2016-07-22 at 14:54 +0000, Azhagappan Balasubramanian
(INST/ECS4) wrote:
> Hello,
>
> Now that we have the concept of requestTicket associated with each
> request and response in Leshan, I have a specific request. I would
> like to create a PR to add cancelRequest(requestTicket) method in
> LwM2mRequestSender interface.
>
> I checked the LWM2M spec and it doesn’t say anything or prohibits from
> cancelling a queued message. Yes of course with cancellation, the
> sequence of messages queued for the LWM2M client is effectively
> altered, which in my opinion, is exactly what the application layer
> would expect if it invokes this method. Also there is one potential
> risk that a message even though cancelled on LWM2M/CoAP level, could
> already be delivered or on the wire to the LWM2M client in which case
> the response would be ignored.
>
> Is there anyone in the community against such a PR? If yes, I would be
> glad to hear your side of the argument. Thanks.
> Regards,
> Bala
>
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