Individual Submission J. Reschke
Internet-Draft
Intended status: Standards Track A. Malhotra
Expires: March 23, 2019
J. Snell
September 19, 2018

HTTP SEARCH Method
draft-snell-search-method-01

Abstract

This specification updates the definition and semantics of the HTTP SEARCH request method originally defined by [RFC5323].

Status of This Memo

This Internet-Draft is submitted to IETF 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 March 23, 2019.

Copyright Notice

Copyright (c) 2018 IETF Trust and the persons identified as the document authors. All rights reserved.

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.


Table of Contents

1. Introduction

This specification updates the HTTP SEARCH method originally defined in [RFC5323].

Many existing HTTP-based applications use the HTTP GET and POST methods in various ways to implement the functionality provided by SEARCH.

Using a GET request with some combination of query parameters included within the request URI (as illustrated in the example below) is arguably the most common mechanism for implementing search in web applications. With this approach, implementations are required to parse the request URI into distinct path (everything before the '?') and query elements (everything after the '?'). The path identifies the resource processing the query (in this case 'http://example.org/feed') while the query identifies the specific parameters of the search operation.

A typical use of HTTP GET for requesting a search

GET /feed?q=foo&limit=10&sort=-published HTTP/1.1
Host: example.org

While there are definite advantages to using GET requests in this manner, the disadvantages should not be overlooked. Specifically:

As an alternative to using GET, many implementations make use of the HTTP POST method to perform queries, as illustrated in the example below. In this case, the input parameters to the search operation are passed along within the request payload as opposed to using the request URI.

A typical use of HTTP GET for requesting a search

POST /feed HTTP/1.1
Host: example.org
Content-Type: application/x-www-form-urlencoded

q=foo&limit=10&sort=-published

This variation, however, suffers from the same basic limitation as GET in that it is not readily apparent -- absent specific knowledge of the resource and server to which the request is being sent -- that a search operation is what is being requested. Web applications use the POST method for a wide variety of uses including the creation or modification of existing resources. Sending the request above to a different server, or even repeatedly sending the request to the same server could have dramatically different effects.

The SEARCH method provides a solution that spans the gap between the use of GET and POST. As with POST, the input to the query operation is passed along within the payload of the request rather than as part of the request URI. Unlike POST, however the semantics of the SEARCH method are specifically defined.

In this document, the key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" are to be interpreted as described in [RFC2119].

2. SEARCH

The SEARCH method is used to initiate a server-side search. Unlike the HTTP GET method, which requests that a server return a representation of the resource identified by the effective request URI (as defined by [RFC7230]), the SEARCH method is used to ask the server to perform a query operation (described by the request payload) over some set of data scoped to the effective request URI. The payload returned in response to a SEARCH cannot be assumed to be a representation of the resource identified by the effective request URI.

The body payload of the request defines the query. Implementations MAY use a request body of any content type with the SEARCH method; however, for backwards compatibility with existing WebDAV implementations, SEARCH requests that use the text/xml or application/xml content types MUST be processed per the requirements established by [RFC5323].

SEARCH requests are both safe and idempotent with regards to the resource identified by the request URI. That is, SEARCH requests do not alter the state of the targeted resource. However, while processing a search request, a server can be expected to allocate computing and memory resources or even create additional HTTP resources through which the response can be retrieved.

A successful response to a SEARCH request is expected to provide some indication as to the final disposition of the search operation. For instance, a successful search that yields no results can be represented by a 204 No Content response. If the response includes a body payload, the payload is expected to describe the results of the search operation. In some cases, the server may choose to respond indirectly to the SEARCH request by returning a 3xx Redirection with a Location header specifying an alternate Request URI from which the search results can be retrieved using an HTTP GET request. Various non-normative examples of successful SEARCH responses are illustrated in Section 4.

The response to a SEARCH request is not cacheable. It ought to be noted, however, that because SEARCH requests are safe and idempotent, responses to a SEARCH MUST NOT invalidate previously cached responses to other requests directed at the same effective request URI.

The semantics of the SEARCH method change to a "conditional SEARCH" if the request message includes an If-Modified-Since, If-Unmodified- Since, If-Match, If-None-Match, or If-Range header field ([RFC7232]). A conditional SEARCH requests that the query be performed only under the circumstances described by the conditional header field(s). It is important to note, however, that such conditions are evaluated against the state of the target resource itself as opposed to the collected results of the search operation.

3. The "Accept-Search" Header Field

The "Accept-Search" response header field MAY be used by a server to directly signal support for the SEARCH method while identifying the specific query format Content-Type's that may be used.

Accept-Search = "Accept-Search" ":" 1#media-type

The Accept-Search header specifies a comma-separated listing of media types (with optional parameters) as defined by [RFC7231], Section 3.1.1.1.

The order of types listed by the Accept-Search header is insignificant.

4. Examples

The non-normative examples in this section make use of a simple, hypothetical plain-text based query syntax based on SQL with results returned as comma-separated values. This is done for illustration purposes only. Implementations are free to use any format they wish on both the request and response.

4.1. Simple SEARCH with a Direct Response

A simple query with a direct response:

  SEARCH /contacts HTTP/1.1
  Host: example.org
  Content-Type: text/query
  Accept: text/csv

  select surname, givenname, email limit 10

Response:

  HTTP/1.1 200 OK
  Content-Type: text/csv

  surname, givenname, email
  Smith, John, john.smith@example.org
  Jones, Sally, sally.jones@example.com
  Dubois, Camille, camille.dubois@example.net

4.2. Simple SEARCH with indirect response (303 See Other)

A simple query with an Indirect Response (303 See Other)

  SEARCH /contacts HTTP/1.1
  Host: example.org
  Content-Type: text/query
  Accept: text/csv

  select surname, givenname, email limit 10

Response:

  HTTP/1.1 303 See Other
  Location: http://example.org/contacts/query123

Fetch Query Response:

  GET /contacts/query123 HTTP/1.1
  Host: example.org

Response:

  HTTP/1.1 200 OK
  Content-Type: text/csv

  surname, givenname, email
  Smith, John, john.smith@example.org
  Jones, Sally, sally.jones@example.com
  Dubois, Camille, camille.dubois@example.net

5. Security Considerations

The SEARCH method is subject to the same general security considerations as all HTTP methods as described in [RFC7231].

6. IANA Considerations

IANA is requested to update the registration of the SEARCH method in the permanent registry at <http://www.iana.org/assignments/http-methods> (see Section 8.1 of [RFC7231]).

Method Name Safe Idempotent Specification
SEARCH Yes Yes Section 2

7. 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.
[RFC4918] Dusseault, L., "HTTP Extensions for Web Distributed Authoring and Versioning (WebDAV)", RFC 4918, DOI 10.17487/RFC4918, June 2007.
[RFC5323] Reschke, J., Reddy, S., Davis, J. and A. Babich, "Web Distributed Authoring and Versioning (WebDAV) SEARCH", RFC 5323, DOI 10.17487/RFC5323, November 2008.
[RFC7230] Fielding, R. and J. Reschke, "Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing", RFC 7230, DOI 10.17487/RFC7230, June 2014.
[RFC7231] Fielding, R. and J. Reschke, "Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content", RFC 7231, DOI 10.17487/RFC7231, June 2014.
[RFC7232] Fielding, R. and J. Reschke, "Hypertext Transfer Protocol (HTTP/1.1): Conditional Requests", RFC 7232, DOI 10.17487/RFC7232, June 2014.
[RFC7234] Fielding, R., Nottingham, M. and J. Reschke, "Hypertext Transfer Protocol (HTTP/1.1): Caching", RFC 7234, DOI 10.17487/RFC7234, June 2014.

Authors' Addresses

Julian Reschke EMail: julian.reschke@greenbytes.de
Ashok Malhotra EMail: ashok.malhotra@oracle.com
James M Snell EMail: jasnell@gmail.com