Orchestrator-workers on Twelve HTTP status codes, by the book

HTTP status codes in RFC 9110: reason phrases, sections and heuristic cacheability

All twelve codes are defined in RFC 9110 (HTTP Semantics). Of these, 203, 206, 308, 405, 410, 414 and 501 are heuristically cacheable. The other five (303, 307, 413, 421, 422) are not. Every claim below comes from https://www.rfc-editor.org/rfc/rfc9110.html, which the workers opened with fetch_page.

Is RFC 9110 still the current specification?

The page header reads "Obsoletes: 2818, 7230, 7231, 7232, 7233, 7235, 7538, 7615, 7694" and has no "Obsoleted by" line (https://www.rfc-editor.org/rfc/rfc9110.html). Web searches by three workers found nothing newer that replaces it.

This check is incomplete. The official status page (https://www.rfc-editor.org/info/rfc9110) returned a 404 error, so no worker could confirm the status there.

How cacheability was decided

Section 15.1 (Overview of Status Codes) at https://www.rfc-editor.org/rfc/rfc9110.html gives the list:

"Responses with status codes that are defined as heuristically cacheable (e.g., 200, 203, 204, 206, 300, 301, 308, 404, 405, 410, 414, and 501 in this specification) can be reused by a cache with heuristic expiration unless otherwise indicated by the method definition or explicit cache controls [CACHING]; all other status codes are not heuristically cacheable."

Workers checked each code's own section against this list, and the two always agreed:

• Cacheable codes: each one's own section says it is cacheable, in the form "A NNN response is heuristically cacheable; …". This covers 203, 206, 308, 405, 410, 414 and 501.
• 206 wording: the 206 section leaves out the "method definition" clause. It says only "unless otherwise indicated by explicit cache controls".
• Non-cacheable codes: the sections for 303, 307, 413, 421 and 422 say nothing about heuristic caching, and none of these codes is on the 15.1 list.
• 303 note: its section says the POST result "can be separately identified, bookmarked, and cached". That refers to the resource the 303 points to, not to the 303 response itself.

Other points

• Changed reason phrases: RFC 9110 calls 413 "Content Too Large" and 422 "Unprocessable Content". No worker opened the older RFCs, so I can't confirm the earlier wording.
• 421 and 422: both are now defined in the core specification, in sections 15.5.20 and 15.5.21.
• Quote formatting: the page wraps its lines. One worker noted that wrapped lines were joined with single spaces in the quotes.

{"answers":[
{"code":"203","reason":"Non-Authoritative Information","section":"15.3.4","heuristicallyCacheable":true,"quote":"This status code allows the proxy to notify recipients when a transformation has been applied, since that knowledge might impact later decisions regarding the content.","url":"https://www.rfc-editor.org/rfc/rfc9110.html"},
{"code":"206","reason":"Partial Content","section":"15.3.7","heuristicallyCacheable":true,"quote":"The 206 (Partial Content) status code indicates that the server is successfully fulfilling a range request for the target resource by transferring one or more parts of the selected representation.","url":"https://www.rfc-editor.org/rfc/rfc9110.html"},
{"code":"303","reason":"See Other","section":"15.4.4","heuristicallyCacheable":false,"quote":"This status code is applicable to any HTTP method.","url":"https://www.rfc-editor.org/rfc/rfc9110.html"},
{"code":"307","reason":"Temporary Redirect","section":"15.4.8","heuristicallyCacheable":false,"quote":"Since the redirection can change over time, the client ought to continue using the original target URI for future requests.","url":"https://www.rfc-editor.org/rfc/rfc9110.html"},
{"code":"308","reason":"Permanent Redirect","section":"15.4.9","heuristicallyCacheable":true,"quote":"The 308 (Permanent Redirect) status code indicates that the target resource has been assigned a new permanent URI and any future references to this resource ought to use one of the enclosed URIs.","url":"https://www.rfc-editor.org/rfc/rfc9110.html"},
{"code":"405","reason":"Method Not Allowed","section":"15.5.6","heuristicallyCacheable":true,"quote":"The origin server MUST generate an Allow header field in a 405 response containing a list of the target resource's currently supported methods.","url":"https://www.rfc-editor.org/rfc/rfc9110.html"},
{"code":"410","reason":"Gone","section":"15.5.11","heuristicallyCacheable":true,"quote":"The 410 (Gone) status code indicates that access to the target resource is no longer available at the origin server and that this condition is likely to be permanent.","url":"https://www.rfc-editor.org/rfc/rfc9110.html"},
{"code":"413","reason":"Content Too Large","section":"15.5.14","heuristicallyCacheable":false,"quote":"The 413 (Content Too Large) status code indicates that the server is refusing to process a request because the request content is larger than the server is willing or able to process.","url":"https://www.rfc-editor.org/rfc/rfc9110.html"},
{"code":"414","reason":"URI Too Long","section":"15.5.15","heuristicallyCacheable":true,"quote":"The 414 (URI Too Long) status code indicates that the server is refusing to service the request because the target URI is longer than the server is willing to interpret.","url":"https://www.rfc-editor.org/rfc/rfc9110.html"},
{"code":"421","reason":"Misdirected Request","section":"15.5.20","heuristicallyCacheable":false,"quote":"The 421 (Misdirected Request) status code indicates that the request was directed at a server that is unable or unwilling to produce an authoritative response for the target URI.","url":"https://www.rfc-editor.org/rfc/rfc9110.html"},
{"code":"422","reason":"Unprocessable Content","section":"15.5.21","heuristicallyCacheable":false,"quote":"For example, this status code can be sent if an XML request content contains well-formed (i.e., syntactically correct), but semantically erroneous XML instructions.","url":"https://www.rfc-editor.org/rfc/rfc9110.html"},
{"code":"501","reason":"Not Implemented","section":"15.6.2","heuristicallyCacheable":true,"quote":"The 501 (Not Implemented) status code indicates that the server does not support the functionality required to fulfill the request.","url":"https://www.rfc-editor.org/rfc/rfc9110.html"}
]}