Problem Details For CoAP APIs
draft-ietf-core-problem-details-01
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft that was ultimately published as RFC 9290.
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|
|---|---|---|---|
| Authors | Thomas Fossati , Jaime Jimenez , Klaus Hartke | ||
| Last updated | 2021-01-14 (Latest revision 2020-07-13) | ||
| Replaces | draft-fossati-core-coap-problem | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
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draft-ietf-core-problem-details-01
CoRE Working Group T. Fossati
Internet-Draft arm
Intended status: Standards Track J. Jiménez
Expires: 14 January 2021 K. Hartke
Ericsson
13 July 2020
Problem Details For CoAP APIs
draft-ietf-core-problem-details-01
Abstract
This document defines a "problem detail" as a way to carry machine-
readable details of errors in a CoAP response to avoid the need to
define new error response formats for CoAP APIs. The proposed format
is inspired by the Problem Details for HTTP APIs defined in RFC 7807.
Discussion Venues
This note is to be removed before publishing as an RFC.
Source for this draft and an issue tracker can be found at
https://github.com/core-wg/core-problem-details (https://github.com/
core-wg/core-problem-details).
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on 14 January 2021.
Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved.
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This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components
extracted from this document must include Simplified BSD License text
as described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. Basic Problem Details . . . . . . . . . . . . . . . . . . . . 3
2.1. Examples . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Additional Problem Details . . . . . . . . . . . . . . . . . 5
3.1. Examples . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Security Considerations . . . . . . . . . . . . . . . . . . . 5
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
6.1. Normative References . . . . . . . . . . . . . . . . . . 6
6.2. Informative References . . . . . . . . . . . . . . . . . 6
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
CoAP [RFC7252] response codes are sometimes not sufficient to convey
enough information about an error to be helpful. This specification
defines a simple and extensible CoRAL [I-D.ietf-core-coral]
vocabulary to suit this purpose. It is designed to be reused by CoAP
APIs, which can identify distinct "problem types" specific to their
needs. Thus, API clients can be informed of both the high-level
error class (using the response code) and the finer-grained details
of the problem (using this vocabulary), as shown in Figure 1.
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+--------+ +--------+
| CoAP | | CoAP |
| Client | | Server |
+--------+ +--------+
| |
| Request |
|----------------->|
| |
|<-----------------|
| Error Response |
| with a CoRAL |
| Document giving |
| Problem Details |
| |
Figure 1: Problem Details
The vocabulary presented is largely inspired by the Problem Details
for HTTP APIs defined in [RFC7807].
1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
2. Basic Problem Details
A CoAP Problem Details is a CoRAL document with the following
elements:
* "type" (id) - The problem type. This is a mandatory element.
* "title" (text) - A short, human-readable summary of the problem
type. It SHOULD NOT change from occurrence to occurrence of the
problem.
* "detail" (text) - A human-readable explanation specific to this
occurrence of the problem.
* "instance" (uri) - A URI reference that identifies the specific
occurrence of the problem. It may or may not yield further
information if dereferenced.
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Consumers MUST use "type" as primary identifiers for the problem
type; the "title" string is advisory and included only for consumers
who are not aware of the semantics of the "type" value.
The "detail" member, if present, ought to focus on helping the client
correct the problem, rather than giving debugging information.
Consumers SHOULD NOT parse the "detail" member for information;
extensions (see Section 3) are more suitable and less error-prone
ways to obtain such information.
Note that the "instance" URI reference may be relative; this means
that it must be resolved relative to the document's base URI, as per
[I-D.ietf-core-coral].
2.1. Examples
This section presents a series of examples of the basic vocabulary in
CoRAL textual format (Section 4 of [I-D.ietf-core-coral]). The
examples are fictitious. No identification with actual products is
intended or should be inferred. All examples involve the same CoAP
problem type with semantics of "unknown key id", defined in the
fictitious namespace "http://vocabulary.private-api.example".
Note that CoRAL documents are exchanged in CoRAL binary format
(Section 3 of [I-D.ietf-core-coral]) in practice. This includes the
use of [I-D.ietf-core-href] as an alternative to URIs that is
optimized for constrained nodes.
The example in Figure 2 has the most compact representation. It
avoids any non-mandatory element. This is suitable for a constrained
receiver that happens to have precise knowledge of the semantics
associated with the "type".
#using pd = <http://example.org/vocabulary/problem-details#>
#using ex = <http://vocabulary.private-api.example/#>
pd:type ex:unknown-key-id
Figure 2: Minimalist
The example in Figure 3 has all the mandatory as well as the optional
elements populated. This format is appropriate for a less
constrained receiver (for example, an edge gateway forwarding to a
log server that needs to gather as much contextual information as
possible, including the problem "headline", details about the error
condition, and an error-specific instance URL).
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#using pd = <http://example.org/vocabulary/problem-details#>
#using ex = <http://vocabulary.private-api.example/#>
pd:type ex:unknown-key-id
pd:title "unknown key id"
pd:detail "Key with id 0x01020304 not registered"
pd:instance <https://private-api.example/errors/5>
Figure 3: Full-Fledged
3. Additional Problem Details
Problem type definitions MAY extend the Problem Details document with
additional elements to convey additional, problem-specific
information.
Clients consuming problem details MUST ignore any such elements that
they do not recognize; this allows problem types to evolve and
include additional information in the future.
3.1. Examples
The example in Figure 4 has all the basic elements as well as an
additional, type-specific element.
#using pd = <http://example.org/vocabulary/problem-details#>
#using ex = <http://vocabulary.private-api.example/#>
pd:type ex:unknown-key-id
pd:title "unknown key id"
pd:detail "Key with id 0x01020304 not registered"
pd:instance <https://private-api.example/errors/5>
ex:key-id 0x01020304
Figure 4: Full Payload and Extensions
4. Security Considerations
Problem Details for CoAP APIs are serialized in the CoRAL binary
format. See Section 11 of [RFC7252] for security considerations
relating to CoAP. See Section 7 of [I-D.ietf-core-coral] for
security considerations relating to CoRAL.
The security and privacy considerations outlined in Section 5 of
[RFC7807] apply in full.
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5. IANA Considerations
TODO.
6. References
6.1. Normative References
[I-D.ietf-core-coral]
Hartke, K., "The Constrained RESTful Application Language
(CoRAL)", Work in Progress, Internet-Draft, draft-ietf-
core-coral-03, 9 March 2020, <http://www.ietf.org/
internet-drafts/draft-ietf-core-coral-03.txt>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC7252] Shelby, Z., Hartke, K., and C. Bormann, "The Constrained
Application Protocol (CoAP)", RFC 7252,
DOI 10.17487/RFC7252, June 2014,
<https://www.rfc-editor.org/info/rfc7252>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
6.2. Informative References
[I-D.ietf-core-href]
Hartke, K., "Constrained Resource Identifiers", Work in
Progress, Internet-Draft, draft-ietf-core-href-03, 9 March
2020, <http://www.ietf.org/internet-drafts/draft-ietf-
core-href-03.txt>.
[RFC7807] Nottingham, M. and E. Wilde, "Problem Details for HTTP
APIs", RFC 7807, DOI 10.17487/RFC7807, March 2016,
<https://www.rfc-editor.org/info/rfc7807>.
Acknowledgments
Mark Nottingham and Erik Wilde, authors of RFC 7807. Carsten
Bormann, Jim Schaad, Christian Amsuess for review and comments on
this document.
Authors' Addresses
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Thomas Fossati
arm
Email: thomas.fossati@arm.com
Jaime Jiménez
Ericsson
Email: jaime@iki.fi
Klaus Hartke
Ericsson
Email: klaus.hartke@ericsson.com
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