[Technical Errata Reported] RFC7234 (5564)

Discussion:

RFC Errata System

2018-11-27 11:37:43 UTC

The following errata report has been submitted for RFC7234,
"Hypertext Transfer Protocol (HTTP/1.1): Caching".

--------------------------------------
You may review the report below and at:
http://www.rfc-editor.org/errata/eid5564

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Type: Technical
Reported by: Bruce Adams <***@yahoo.co.uk>

Section: 4.2.4

Original Text
-------------
A cache MUST NOT send stale responses unless it is disconnected
(i.e., it cannot contact the origin server or otherwise find a
forward path) or doing so is explicitly allowed (e.g., by the
max-stale request directive; see Section 5.2.1).

Corrected Text
--------------
A cache SHOULD NOT send stale responses unless it is disconnected
(i.e., it cannot contact the origin server or otherwise find a
forward path) or doing so is explicitly allowed (e.g., by the
max-stale request directive; see Section 5.2.1).

A cache MAY send stale responses if a cache-control extension for
stale content such as "stale-while-revalidate" is used
(see RFC5861).

Notes
-----
The original text seems to conflict with https://tools.ietf.org/html/rfc5861#section-3

3. The stale-while-revalidate Cache-Control Extension

When present in an HTTP response, the stale-while-revalidate Cache-
Control extension indicates that caches MAY serve the response in
which it appears after it becomes stale, up to the indicated number
of seconds.

stale-while-revalidate = "stale-while-revalidate" "=" delta-seconds

If a cached response is served stale due to the presence of this
extension, the cache SHOULD attempt to revalidate it while still
serving stale responses (i.e., without blocking).

See also https://stackoverflow.com/questions/53324538/rest-low-latency-how-should-i-reply-to-a-get-while-an-upload-is-pending

Instructions:
-------------
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use "Reply All" to discuss whether it should be verified or
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--------------------------------------
RFC7234 (draft-ietf-httpbis-p6-cache-26)
--------------------------------------
Title : Hypertext Transfer Protocol (HTTP/1.1): Caching
Publication Date : June 2014
Author(s) : R. Fielding, Ed., M. Nottingham, Ed., J. Reschke, Ed.
Category : PROPOSED STANDARD
Source : Hypertext Transfer Protocol Bis APP
Area : Applications
Stream : IETF
Verifying Party : IESG

Mark Nottingham

2018-11-27 22:50:31 UTC

Permalink

REJECT. Extensions are explicitly allowed to override requirements, and making this a SHOULD would be too confusing (as many would read it as "optional").

Post by RFC Errata System
The following errata report has been submitted for RFC7234,
"Hypertext Transfer Protocol (HTTP/1.1): Caching".
--------------------------------------
http://www.rfc-editor.org/errata/eid5564
--------------------------------------
Type: Technical
Section: 4.2.4
Original Text
-------------
A cache MUST NOT send stale responses unless it is disconnected
(i.e., it cannot contact the origin server or otherwise find a
forward path) or doing so is explicitly allowed (e.g., by the
max-stale request directive; see Section 5.2.1).
Corrected Text
--------------
A cache SHOULD NOT send stale responses unless it is disconnected
(i.e., it cannot contact the origin server or otherwise find a
forward path) or doing so is explicitly allowed (e.g., by the
max-stale request directive; see Section 5.2.1).
A cache MAY send stale responses if a cache-control extension for
stale content such as "stale-while-revalidate" is used
(see RFC5861).
Notes
-----
The original text seems to conflict with https://tools.ietf.org/html/rfc5861#section-3
3. The stale-while-revalidate Cache-Control Extension
When present in an HTTP response, the stale-while-revalidate Cache-
Control extension indicates that caches MAY serve the response in
which it appears after it becomes stale, up to the indicated number
of seconds.
stale-while-revalidate = "stale-while-revalidate" "=" delta-seconds
If a cached response is served stale due to the presence of this
extension, the cache SHOULD attempt to revalidate it while still
serving stale responses (i.e., without blocking).
See also https://stackoverflow.com/questions/53324538/rest-low-latency-how-should-i-reply-to-a-get-while-an-upload-is-pending
-------------
This erratum is currently posted as "Reported". If necessary, please
use "Reply All" to discuss whether it should be verified or
rejected. When a decision is reached, the verifying party
can log in to change the status and edit the report, if necessary.
--------------------------------------
RFC7234 (draft-ietf-httpbis-p6-cache-26)
--------------------------------------
Title : Hypertext Transfer Protocol (HTTP/1.1): Caching
Publication Date : June 2014
Author(s) : R. Fielding, Ed., M. Nottingham, Ed., J. Reschke, Ed.
Category : PROPOSED STANDARD
Source : Hypertext Transfer Protocol Bis APP
Area : Applications
Stream : IETF
Verifying Party : IESG

--
Mark Nottingham https://www.mnot.net/

Mark Nottingham

2018-11-30 00:39:33 UTC

Permalink

Hi Bruce!

See:
https://httpwg.org/specs/rfc7234.html#cache.control.extensions

Along with this text in sections 3 and 4:
"Note that any of the requirements listed above can be overridden by a cache-control extension; see Section 5.2.3."

Cheers,

Hi,
That makes sense. I didn't realise extension could override, particularly in the case of a "MUST".
For my own education where would I find this policy?
If I interpret this correctly I can for a ReST service return a stale document and
"warning 111 response is stale" provided my response also includes "stale-while-revalidate" from rfc5861.
Regards,
Bruec.
REJECT. Extensions are explicitly allowed to override requirements, and making this a SHOULD would be too confusing (as many would read it as "optional").

--
Mark Nottingham https://www.mnot.net/