Network Working Group S. Dalal
Internet-Draft
Intended status: Standards Track E. Wilde
Expires: August 30, 2019 February 26, 2019
The Deprecation HTTP Header
draft-dalal-deprecation-header-00
Abstract
The HTTP Deprecation response header can be used to signal to
consumers of a URI-identified resource that the use of the resource
has been deprecated. Additionally, the deprecation link relation can
be used to link to a resource that provides additional context for
the deprecation, and possibly ways in which clients can find a
replacement for the deprecated resource.
Status of This Memo
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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on August 30, 2019.
Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved.
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Notational Conventions . . . . . . . . . . . . . . . . . 3
2. The Deprecation HTTP Response Header Field . . . . . . . . . 3
2.1. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1.1. Version . . . . . . . . . . . . . . . . . . . . . . . 4
2.1.2. Date . . . . . . . . . . . . . . . . . . . . . . . . 4
3. The Deprecation Link Relation Type . . . . . . . . . . . . . 5
3.1. Documentation . . . . . . . . . . . . . . . . . . . . . . 5
3.2. Policy . . . . . . . . . . . . . . . . . . . . . . . . . 6
4. Recommend Replacement . . . . . . . . . . . . . . . . . . . . 6
5. Sunset . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
6.1. The Deprecation Response Header Field . . . . . . . . . . 7
6.2. The Deprecation Link Relation Type . . . . . . . . . . . 7
7. Implementation Status . . . . . . . . . . . . . . . . . . . . 8
8. Security Considerations . . . . . . . . . . . . . . . . . . . 9
9. Example . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 10
10.1. Normative References . . . . . . . . . . . . . . . . . . 10
10.2. Informative References . . . . . . . . . . . . . . . . . 11
Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12
1. Introduction
Deprecation of a URI-identified resource is a technique to
communicate information about the lifecycle of a resource. It
encourages applications to migrate away from the resource and
discourage applications from forming new dependencies on the
resource, and informs applications of the risk of continuing
dependence upon the resource.
The act of deprecation does not change any behavior of the resource.
It just informs client of the fact that a resource is deprecated.
The Deprecation HTTP response header field MAY be used to convey this
fact at runtime to clients. The header field can carry additional
information such as since when the deprecation is in effect.
In addition to the Deprecation header field the resource provider can
use other header fields to convey additional information related to
deprecation. For example, information such as where to find
documentation related to the deprecation or what should be used as an
alternate and when the deprecated resource would be unreachable, etc.
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Alternates of a resource can be similar resource(s) or a newer
version of the same resource.
1.1. Notational Conventions
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.
This specification uses the Augmented Backus-Naur Form (ABNF)
notation of [RFC5234] and includes, by reference, the "token" rule,
DQUOTE (double quote) rule, the SP (space) rule and the "rule"
extension that allows for compact definition of comma-separated lists
using a '#' operator (similar to how the '*' operator indicates
repetition), HTTP-date rule as defined within Sections 3.2.6 and 7 of
[RFC7230] and Section 7.1.1 of [RFC7231].
2. The Deprecation HTTP Response Header Field
The "Deprecation" HTTP response header field allows a server to
communicate to a client that the URI-identified resource in context
of the message is deprecated. It can also provide information that
the resource is deprecated since which version.
2.1. Syntax
The "Deprecation" response header contains the header name
"Deprecation" followed by a ":" and a property(s). Each property
consists of a name-value-pair. Servers SHOULD NOT send Deprecation
headers that fail to conform to the following grammar:
deprecation-header = "Deprecation:" SP "version"=vval, "date"=dval,
*( extension )
extension = property-name "=" property-value
property-name = DQUOTE token DQUOTE
token = <token, defined as in [RFC7230], Section 3.2.6>
vval = property-value
property-value = DQUOTE *( pchar ) DQUOTE
pchar = %x23 / %x2B-3A / %x41-5A / %x61-7A / %x7C
; US-ASCII characters
dval = DQUOTE HTTP-date DQUOTE
Note that some of the grammatical terms above reference documents
that use different grammatical notations than this document (which
uses ABNF from [RFC5234]).
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Servers SHOULD NOT include more than one "Deprecation" header field
in the same response. If a server sends multiple responses
containing "Deprecation" headers concurrently to the user agent
(e.g., when communicating with the user agent over multiple sockets),
these responses create a "race condition" that can lead to
unpredictable behavior.
The value of "Deprecation" response header field could consist of at
least 1 standard property: "date" or "version" as shown below.
Either of "version" or "date" is REQUIRED and both are also allowed.
Deprecation: version="version", date="date"
The value of the "version" property, if present, could be the version
of the resource that is deprecated. The value of "version" would be
an opaque version identifier. For resources that use date-based
versioning scheme, the value would be accordingly.
Following example indicates that the version v1 of the resource in
context is deprecated.
Deprecation: version="v1"
Following example shows that the version 2018-11-08 (November 8,
2018) of the resource in context is deprecated. Here the versioning
scheme used is date-based.
Deprecation: version="2018-11-08"
The value of "date" property, if present, would be the date when
resource was deprecated. It would be in the form of a quoted HTTP-
date timestamp, as defined in Section 7.1.1.1 of [RFC7231].
Following example shows that the resource in context is deprecated on
Friday, November 11, 2018 at 23:59:59 GMT.
Deprecation: date="Fri, 11 Nov 2018 23:59:59 GMT"
Date could be in future too. If the value of "date" is in future, it
means that the resource would be deprecated on the given date in
future.
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3. The Deprecation Link Relation Type
In addition to the Deprecation HTTP header, the server could use a
"Link" header(s) to communicate to the client where to find more
information about deprecation of the resource in context. This
information could be in the form of documentation of the resource
including details about the deprecation related aspects of the
resource or the deprecation policy of the resource provider or both
for example.
3.1. Documentation
For a URI-identified resource, deprecation could involve one or more
parts of request, response or both. These parts could be one or more
of the following.
o URI - deprecation of one ore more query parameter(s) or path
element(s)
o method - HTTP method for the resource is deprecated
o request header - one or more HTTP request header(s) is deprecated
o response header - HTTP response header(s) is deprecated
o request body - request body contains one or more deprecated
element(s)
o response body - response body contains one or more deprecated
element(s)
The purpose of the "Deprecation" header is to provide just enough
"hints" about the deprecation to the client application developer.
It is safe to assume that on reception of the "Deprecation" header,
the client developer would look up the resource's documentation in
order to find deprecation related semantics. The resource developer
could provide a link to the resource documentation using a "Link"
header with relation type "deprecation" as shown below.
Deprecation: version="v1"
Link: <https://developer.example.com/v1/customers>; rel="deprecation"
type="text/html"
where content at "https://developer.example.com/v1/customers" would
be annotated to show deprecation of the relevant parts of the
"customers" resource.
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3.2. Policy
Resource provider would typically document versioning and deprecation
policy with the resource documentation. To inform the client
application developer of the deprecation policy, the resource
provider could use the "deprecation" relation type as shown below.
Deprecation: version="v1"
Link: <https://developer.example.com/deprecation>; rel="deprecation"
type="text/html"
where deprecation policy of the resource provider "example.com" is
described at "https://developer.example.com/deprecation".
4. Recommend Replacement
"Link" [RFC8288] header could be used in addition to the
"Deprecation" header to recommend the client application about
available alternates to the deprecated resource. Following relation
types as defined in [RFC8288] are RECOMMENDED to use for the purpose.
o "successor-version": Points to a resource containing the successor
version. [RFC5829]
o "latest-version": Points to a resource containing the latest
(e.g., current) version. [RFC5829]
o "alternate": Designates a substitute. [W3C.REC-html401-19991224]
Following example provides link to the successor version of the v1
version of "customer" resource that is deprecated.
Deprecation: version="v1"
Link: <https://api.example.com/v2/customers>; rel="successor-version"
This example provides link to an alternate resource to the "customer"
resource that is deprecated.
Deprecation: version="2018-11-11"
Link: <https://api.example.com/v1/clients>; rel="alternate"
5. Sunset
In addition to the deprecation related information, if the resource
provider wants to convey to the client application that the
deprecated resource is expected to become unresponsive at a specific
point in time, the [Sunset] header could be used in addition to the
"Deprecation" header.
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Following example indicates that the resource in context has been
deprecated since version v2 and its sunset date is Friday, November
11, 2020 at 23:59:59 GMT.
Deprecation: version="v2"
Sunset: Fri, 11 Nov 2020 23:59:59 GMT
Following example shows that the resource in context has been
deprecated since Friday, November 11, 2018 at 23:59:59 GMT and its
sunset date is Friday, November 11, 2020 at 23:59:59 GMT.
Deprecation: date="Fri, 11 Nov 2018 23:59:59 GMT"
Sunset: Fri, 11 Nov 2020 23:59:59 GMT
6. IANA Considerations
6.1. The Deprecation Response Header Field
The "Deprecation" response header should be added to the permanent
registry of message header fields (see [RFC3864]), taking into
account the guidelines given by HTTP/1.1 [RFC7231].
Header Field Name: Deprecation
Applicable Protocol: Hypertext Transfer Protocol (HTTP)
Status: Standard
Author: Sanjay Dalal <sanjay.dalal@cal.berkeley.edu>,
Erik Wilde <erik.wilde@dret.net>
Change controller: IETF
Specification document: this specification,
Section 2 "The Deprecation HTTP Response Header Field"
6.2. The Deprecation Link Relation Type
The "deprecation" link relation type should be added to the permanent
registry of link relation types according to Section 4.2 of
[RFC8288]:
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Relation Type: deprecation
Applicable Protocol: Hypertext Transfer Protocol (HTTP)
Status: Standard
Author: Sanjay Dalal <sanjay.dalal@cal.berkeley.edu>,
Erik Wilde <erik.wilde@dret.net>
Change controller: IETF
Specification document: this specification,
Section 3 "The Deprecation Link Relation Type"
7. Implementation Status
Note to RFC Editor: Please remove this section before publication.
This section records the status of known implementations of the
protocol defined by this specification at the time of posting of this
Internet-Draft, and is based on a proposal described in [RFC7942].
The description of implementations in this section is intended to
assist the IETF in its decision processes in progressing drafts to
RFCs. Please note that the listing of any individual implementation
here does not imply endorsement by the IETF. Furthermore, no effort
has been spent to verify the information presented here that was
supplied by IETF contributors. This is not intended as, and must not
be construed to be, a catalog of available implementations or their
features. Readers are advised to note that other implementations may
exist.
According to RFC 7942, "this will allow reviewers and working groups
to assign due consideration to documents that have the benefit of
running code, which may serve as evidence of valuable experimentation
and feedback that have made the implemented protocols more mature.
It is up to the individual working groups to use this information as
they see fit".
Organization: Zapier
Description: Zapier uses two custom HTTP headers named "X-API-
Deprecation-Date" and "X-API-Deprecation-Info"
Reference: https://zapier.com/engineering/api-geriatrics/
Organization: IBM
IBM uses a custom HTTP header named "Deprecated"
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Reference:
https://www.ibm.com/support/knowledgecenter/en/SS42VS_7.3.1/
com.ibm.qradar.doc/c_rest_api_getting_started.html
Organization: Ultipro
Description: Ultipro uses the HTTP "Warning" header as described in
Section 5.5 of [RFC7234] with code "299"
Reference: https://connect.ultipro.com/api-deprecation
Organization: Clearbit
Description: Clearbit uses a custom HTTP header named "X-API-Warn"
Reference: https://blog.clearbit.com/dealing-with-deprecation/
Organization: PayPal
Description: PayPal uses a custom HTTP header named "PayPal-
Deprecated"
Reference: https://github.com/paypal/api-standards/blob/master/api-
style-guide.md#runtime
8. Security Considerations
The content of a "Link" header field is not secure, private or
integrity-guaranteed, and due caution should be exercised when using
it. Use of Transport Layer Security (TLS) with HTTP ([RFC7230] is
currently the only end-to-end way to provide such protection.
The suggested "Link" header fields make extensive use of IRIs and
URIs. See [RFC3987] for security considerations relating to IRIs.
See [RFC3986] for security considerations relating to URIs. See
[RFC7230] for security considerations relating to HTTP headers.
Applications that take advantage of typed links should consider the
attack vectors opened by automatically following, trusting, or
otherwise using links gathered from the HTTP headers. In particular,
Link headers that use the "successor-version", "latest-version" or
"alternate" relation types should be treated with due caution. See
[RFC5829] for security considerations relating to these link relation
types.
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9. Example
Just deprecation header without any Link headers.
Deprecation: version="v1"
Deprecation header with link to the successor version.
Deprecation: version="v1"
Link: <https://api.example.com/v2/customers>; rel="successor-version"
Deprecation header with links for the successor version and for the
API developer's deprecation policy. Also, it shows sunset date for
the deprecated version (v1).
Deprecation: version="v1"
Sunset: Fri, 11 Nov 2020 23:59:59 GMT
Link: <https://api.example.com/v2/customers>; rel="successor-version"
Link: <https://developer.example.com/deprecation>; rel="deprecation"
10. References
10.1. Normative References
[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>.
[RFC3864] Klyne, G., Nottingham, M., and J. Mogul, "Registration
Procedures for Message Header Fields", BCP 90, RFC 3864,
DOI 10.17487/RFC3864, September 2004,
<https://www.rfc-editor.org/info/rfc3864>.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, DOI 10.17487/RFC3986, January 2005,
<https://www.rfc-editor.org/info/rfc3986>.
[RFC3987] Duerst, M. and M. Suignard, "Internationalized Resource
Identifiers (IRIs)", RFC 3987, DOI 10.17487/RFC3987,
January 2005, <https://www.rfc-editor.org/info/rfc3987>.
[RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234,
DOI 10.17487/RFC5234, January 2008,
<https://www.rfc-editor.org/info/rfc5234>.
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[RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Message Syntax and Routing",
RFC 7230, DOI 10.17487/RFC7230, June 2014,
<https://www.rfc-editor.org/info/rfc7230>.
[RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Semantics and Content", RFC 7231,
DOI 10.17487/RFC7231, June 2014,
<https://www.rfc-editor.org/info/rfc7231>.
[RFC7234] Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
Ed., "Hypertext Transfer Protocol (HTTP/1.1): Caching",
RFC 7234, DOI 10.17487/RFC7234, June 2014,
<https://www.rfc-editor.org/info/rfc7234>.
[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>.
[RFC8288] Nottingham, M., "Web Linking", RFC 8288,
DOI 10.17487/RFC8288, October 2017,
<https://www.rfc-editor.org/info/rfc8288>.
10.2. Informative References
[Deprecation]
Marks, S., "JEP 277 - Enhanced Deprecation", 2017,
<http://openjdk.java.net/jeps/277>.
[RFC5829] Brown, A., Clemm, G., and J. Reschke, Ed., "Link Relation
Types for Simple Version Navigation between Web
Resources", RFC 5829, DOI 10.17487/RFC5829, April 2010,
<https://www.rfc-editor.org/info/rfc5829>.
[RFC7942] Sheffer, Y. and A. Farrel, "Improving Awareness of Running
Code: The Implementation Status Section", BCP 205,
RFC 7942, DOI 10.17487/RFC7942, July 2016,
<https://www.rfc-editor.org/info/rfc7942>.
[Sunset] Wilde, E., "The Sunset HTTP Header Field", 2019,
<https://tools.ietf.org/html/
draft-wilde-sunset-header-11>.
The authors would like to thank Mark Nottingham and Nikhil Kolekar
for reviewing this specification.
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The authors take all responsibility for errors and omissions.
Authors' Addresses
Sanjay Dalal
Email: sanjay.dalal@cal.berkeley.edu
URI: https://github.com/sdatspun2
Erik Wilde
Email: erik.wilde@dret.net
URI: http://dret.net/netdret
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