Network Working Group B. de hOra
Internet-Draft Zalando SE
Intended status: Informational June 15, 2016
Expires: December 17, 2016
The respond-sync Prefer header preference
draft-dehora-respond-sync-00
Abstract
[RFC7240] standardizes a means of indicating client preferences using
the "Prefer" header. This specification defines a "Prefer" header
preference extension to indicate synchronous processing, called
"respond-sync".
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1. Introduction
[RFC7240] standardizes a means of indicating client preferences using
the "Prefer" header. This specification defines a "Prefer" header
preference to indicate synchronous processing, called "respond-sync".
1.1. Terminology
The keywords MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD,
SHOULD NOT, RECOMMENDED, MAY, and OPTIONAL, when they appear in this
document, are to be interpreted as described in [RFC2119].
2. The "respond-sync" Preference
The "respond-sync" preference indicates that the client prefers the
server to respond synchronously to a request. For instance, in the
case where the server would respond with a 202 (Accepted) response
but the client is willing to wait, the server MAY honor the "respond-
sync" preference by returning a 201 (Created) or a 200 (Ok) response
instead.
ABNF [RFC5234]:
respond-sync = "respond-sync"
Clients MAY send a "wait" preference in conjunction with the
"respond-sync" preference to indicate an upper bound on how long it
is willing to wait for the server to process the request.
The motivation for the "respond-sync" preference is to support
synchronous request handling by allowing a client to indicate to a
server its preference for synchronous and non-202 responses where the
server would normally return a 202 (Accepted) response, but not
require specifying timing directives as per the "wait" preference
defined in [RFC7240].
An example request specifying the "respond-sync" preference:
POST /collection HTTP/1.1
Host: example.org
Content-Type: application/json
Prefer: respond-sync
{"property": "value"}
An example synchronous response using 201 (Created):
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HTTP/1.1 201 Created
Location: https://example.org/collection/123
3. IANA Considerations
If this work is accepted, IANA is requested to register the "respond-
sync" preference per [RFC7240] to the HTTP Preferences registry as
follows:
o Preference: respond-sync
o Value: None
o Optional Parameters: None
o Description: Indicates the client prefers that the server respond
synchronously to a request.
o Reference: This specification, Section 2.
4. Security Considerations
A server could incur greater costs in attempting to comply with a
synchronous preference than performing work asynchronously.
Unconditional compliance from a server could allow the use of the
preference for denial of service when presented by multiple clients.
A server can ignore the preference to avoid allocating resources to
the request that it does not wish to commit.
5. Informative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234,
DOI 10.17487/RFC5234, January 2008,
<http://www.rfc-editor.org/info/rfc5234>.
[RFC7240] Snell, J., "Prefer Header for HTTP", RFC 7240,
DOI 10.17487/RFC7240, June 2014,
<http://www.rfc-editor.org/info/rfc7240>.
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Author's Address
Bill de hOra
Zalando SE
Email: bill@dehora.net
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