[core] More precision about CoAP Observe with FETCH
Simon Bernard <contact@simonbernard.eu> Tue, 29 June 2021 09:18 UTC
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From: Simon Bernard <contact@simonbernard.eu>
To: "core@ietf.org WG" <core@ietf.org>
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Date: Tue, 29 Jun 2021 11:18:36 +0200
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Subject: [core] More precision about CoAP Observe with FETCH
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Hi all,
The PATCH and FETCH Methods for the Constrained Application
Protocol (CoAP) (https://datatracker.ietf.org/doc/html/rfc8132" rel="nofollow">RFC8132)
says that FETCH can be used with https://datatracker.ietf.org/doc/html/rfc7641" rel="nofollow">RFC7641
(Observing Resources in CoAP)
But "CoAP Observe" seems to be designed with a "GET without payload" in mind.https://datatracker.ietf.org/doc/html/rfc8132#section-2.4" rel="nofollow">2.4. Working with Observe The Observe option [https://datatracker.ietf.org/doc/html/rfc7641" title='"Observing Resources in the Constrained Application Protocol (CoAP)"' rel="nofollow">RFC7641] can be used with a FETCH request as it can be used with a GET request
E.g. it says :
https://datatracker.ietf.org/doc/html/rfc7641#section-3.1" rel="nofollow">3.1. Request
A client registers its interest in a resource by issuing a GET
request with an Observe Option set to 0 (register). If the server
returns a 2.xx response that includes an Observe Option as well, the
server has successfully added an entry with the client endpoint and
request token to the list of observers of the target resource, and
the client will be notified of changes to the resource state.
Like a fresh response can be used to satisfy a request without
contacting the server, the stream of updates resulting from one
observation request can be used to satisfy another (observation or
normal GET) request if the target resource is the same. A client
MUST aggregate such requests and MUST NOT register more than once for
the same target resource. The target resource is identified by all
options in the request that are part of the Cache-Key. This includes,
for example, the full request URI and the Accept Option.
The target resource is not identified by the payload. So 2 FETCH
requests on same resource with 2 different payload seem to not be
allowed ?
Is it intended or just an oversight ? if this is intended, is
there any particular reason about this ?
Simon
- [core] More precision about CoAP Observe with FET… Simon Bernard
- Re: [core] More precision about CoAP Observe with… Jon Shallow
- Re: [core] More precision about CoAP Observe with… Simon Bernard
- Re: [core] More precision about CoAP Observe with… Simon Bernard
- Re: [core] More precision about CoAP Observe with… Jon Shallow