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".

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
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   This Internet-Draft will expire on December 17, 2016.

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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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