Internet DRAFT - draft-snell-search-method
draft-snell-search-method
Network Working Group J. Reschke
Internet-Draft greenbytes
Updates: 5323 (if approved) A. Malhotra
Intended status: Standards Track
Expires: March 6, 2021 J.M. Snell
September 2, 2020
HTTP SEARCH Method
draft-snell-search-method-02
Abstract
This specification updates the definition and semantics of the HTTP
SEARCH request method originally defined by RFC 5323.
Editorial Note
This note is to be removed before publishing as an RFC.
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Copyright Notice
Copyright (c) 2020 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/
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Please review these documents carefully, as they describe your rights
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. SEARCH . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. The "Accept-Search" Header Field . . . . . . . . . . . . . . 5
4. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4.1. Simple SEARCH with a Direct Response . . . . . . . . . . 6
4.2. Simple SEARCH with indirect response (303 See Other) . . 6
5. Security Considerations . . . . . . . . . . . . . . . . . . . 7
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
7. Normative References . . . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
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
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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:
o Without specific knowledge of the resource and server to which the
GET request is being sent, there is no way for the client to know
that a search operation is being requested. Identical requests
sent to two different servers can implement entirely different
semantics.
o Encoding query parameters directly into the request URI
effectively casts every possible combination of query inputs as
distinct resources. For instance, because mechanisms such as HTTP
caching handle request URIs as opaque character sequences, queries
such as 'http://example.org/?q=foo' and
'http://example.org/?q=Foo' will be treated as entirely separate
resources even if they yield identical results.
o While most modern browser and server implementations allow for
long request URIs, there is no standardized minimum or maximum
length for URIs in general. Many resource constrained devices
enforce strict limits on the maximum number of characters that can
be included in a URI. Such limits can prove impractical for large
or complex query parameters.
o Query expressions included within a request URI must either be
restricted to relatively simple key value pairs or encoded such
that the query can be safely represented in the limited character-
set allowed by URL standards. Such encoding can add significant
complexity, introduce bugs, or otherwise reduce the overall
visibility of the query being requested.
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
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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
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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.
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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:
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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 |
+-------------+------+------------+---------------+
Table 1
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,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC5323] Reschke, J., Ed., Reddy, S., Davis, J., and A. Babich,
"Web Distributed Authoring and Versioning (WebDAV)
SEARCH", RFC 5323, DOI 10.17487/RFC5323, November 2008,
<https://www.rfc-editor.org/info/rfc5323>.
[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>.
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[RFC7232] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Conditional Requests", RFC 7232,
DOI 10.17487/RFC7232, June 2014,
<https://www.rfc-editor.org/info/rfc7232>.
Authors' Addresses
Julian Reschke
greenbytes GmbH
Hafenweg 16
48155 Münster
Germany
Email: julian.reschke@greenbytes.de
URI: https://greenbytes.de/tech/webdav/
Ashok Malhotra
Email: malhotrasahib@gmail.com
James M Snell
Email: jasnell@gmail.com
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