draft-ietf-httpbis-cache-header-01.txt   draft-ietf-httpbis-cache-header-02.txt 
HTTP M. Nottingham HTTP M. Nottingham
Internet-Draft Fastly Internet-Draft Fastly
Intended status: Standards Track November 2, 2019 Intended status: Standards Track November 4, 2019
Expires: May 5, 2020 Expires: May 7, 2020
The Cache-Status HTTP Response Header The Cache-Status HTTP Response Header
draft-ietf-httpbis-cache-header-01 draft-ietf-httpbis-cache-header-02
Abstract Abstract
To aid debugging, HTTP caches often append headers to a response To aid debugging, HTTP caches often append headers to a response
detailing how they handled the request. This specification codifies detailing how they handled the request. This specification codifies
that practice and updates it for HTTP's current caching model. that practice and updates it for HTTP's current caching model.
Note to Readers Note to Readers
_RFC EDITOR: please remove this section before publication_ _RFC EDITOR: please remove this section before publication_
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on May 5, 2020. This Internet-Draft will expire on May 7, 2020.
Copyright Notice Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of (https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Notational Conventions . . . . . . . . . . . . . . . . . 3 1.1. Notational Conventions . . . . . . . . . . . . . . . . . 3
2. The Cache-Status HTTP Response Header . . . . . . . . . . . . 3 2. The Cache-Status HTTP Response Header . . . . . . . . . . . . 3
2.1. The fwd parameter . . . . . . . . . . . . . . . . . . . . 4 2.1. The fwd parameter . . . . . . . . . . . . . . . . . . . . 4
2.2. The fwd-res parameter . . . . . . . . . . . . . . . . . . 4 2.2. The fwd-res parameter . . . . . . . . . . . . . . . . . . 4
2.3. The fwd-stored parameter . . . . . . . . . . . . . . . . 4 2.3. The fwd-stored parameter . . . . . . . . . . . . . . . . 5
2.4. The res-fresh parameter . . . . . . . . . . . . . . . . . 5 2.4. The res-fresh parameter . . . . . . . . . . . . . . . . . 5
2.5. The cache-fresh parameter . . . . . . . . . . . . . . . . 5 2.5. The cache-fresh parameter . . . . . . . . . . . . . . . . 5
2.6. The collapse-hit parameter . . . . . . . . . . . . . . . 5 2.6. The collapse-hit parameter . . . . . . . . . . . . . . . 5
2.7. The collapse-wait parameter . . . . . . . . . . . . . . . 5 2.7. The collapse-wait parameter . . . . . . . . . . . . . . . 5
2.8. The key parameter . . . . . . . . . . . . . . . . . . . . 5 2.8. The key parameter . . . . . . . . . . . . . . . . . . . . 6
3. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 6
4. Security Considerations . . . . . . . . . . . . . . . . . . . 6 4. Security Considerations . . . . . . . . . . . . . . . . . . . 7
5. References . . . . . . . . . . . . . . . . . . . . . . . . . 7 5. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
5.1. Normative References . . . . . . . . . . . . . . . . . . 7 5.1. Normative References . . . . . . . . . . . . . . . . . . 7
5.2. Informative References . . . . . . . . . . . . . . . . . 7 5.2. Informative References . . . . . . . . . . . . . . . . . 8
5.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 8 5.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 8 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction 1. Introduction
To aid debugging, HTTP caches often append headers to a response To aid debugging, HTTP caches often append headers to a response
detailing how they handled the request. detailing how they handled the request.
Unfortunately, the semantics of these headers are often unclear, and Unfortunately, the semantics of these headers are often unclear, and
both the semantics and syntax used vary greatly between both the semantics and syntax used vary greatly between
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cache-fresh = sh-integer cache-fresh = sh-integer
collapse-hit = sh-boolean collapse-hit = sh-boolean
collapse-wait = sh-integer collapse-wait = sh-integer
key = sh-string key = sh-string
2.1. The fwd parameter 2.1. The fwd parameter
"fwd" indicates why the request went forward. If it is not present, "fwd" indicates why the request went forward. If it is not present,
the value defaults to "none". the value defaults to "none".
It can have one of the following values: * none - The request did not It can have one of the following values:
go forward; i.e., it was a hit, and was served from the cache. *
bypass - The cache was configured to not handle this request * uri- o none - The request did not go forward; i.e., it was a hit, and was
miss - The cache did not contain any responses that matched the served from the cache.
request URI * vary-miss - The cache contained a response that matched
the request URI, but could not select a response based upon this o bypass - The cache was configured to not handle this request
request's headers. * miss - The cache did not contain any responses
that could be used to satisfy this request (to be used when an o uri-miss - The cache did not contain any responses that matched
implementation cannot distinguish between uri-miss and vary-miss) * the request URI
res-stale - The cache was able to select a response for the request,
but it was stale * req-stale - The cache was able to select a fresh o vary-miss - The cache contained a response that matched the
response for the request, but client request headers (e.g., Cache- request URI, but could not select a response based upon this
Control request directives) did not allow its use request's headers.
o miss - The cache did not contain any responses that could be used
to satisfy this request (to be used when an implementation cannot
distinguish between uri-miss and vary-miss)
o res-stale - The cache was able to select a response for the
request, but it was stale
o req-stale - The cache was able to select a fresh response for the
request, but client request headers (e.g., Cache-Control request
directives) did not allow its use
2.2. The fwd-res parameter 2.2. The fwd-res parameter
"fwd-res" indicates what the result of the forward request was. It "fwd-res" indicates what the result of the forward request was. It
is only valid when fwd is "res-stale" or "req-stale", and defaults to is only valid when fwd is "res-stale" or "req-stale", and defaults to
"full" if not present when fwd is one of those values. "full" if not present when fwd is one of those values.
It can have one of the following values: * full - indicates that the It can have one of the following values:
response was a complete response (any status code except 304 Not
Modified and 206 Partial Response) * partial - indicates that the o full - indicates that the response was a complete response (any
response was a 206 Partial Response * notmod - indicates that the status code except 304 Not Modified and 206 Partial Response)
response was a 304 Not Modified
o partial - indicates that the response was a 206 Partial Response
o notmod - indicates that the response was a 304 Not Modified
2.3. The fwd-stored parameter 2.3. The fwd-stored parameter
"fwd-stored" indicates whether the cache stored the response; a true "fwd-stored" indicates whether the cache stored the response; a true
value indicates that it did. Only valid when fwd is not "none". value indicates that it did. Only valid when fwd is not "none".
2.4. The res-fresh parameter 2.4. The res-fresh parameter
"res-fresh" indicates the response's remaining freshness lifetime (as "res-fresh" indicates the response's remaining freshness lifetime (as
per [I-D.ietf-httpbis-cache], Section 4.2.1), as an integer number of per [I-D.ietf-httpbis-cache], Section 4.2.1), as an integer number of
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