[
https://issues.apache.org/jira/browse/COUCHDB-2259?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14043186#comment-14043186
]
Robert Newson commented on COUCHDB-2259:
----------------------------------------
It is true that a given revision of a document does not change but the GET
request might change from a 200 response to a 404 response, which is why caches
must revalidate with the origin server.
Be assured that CouchDB developers are very familiar with the HTTP 1.1
specification and the caching model in particular. We have deliberately chosen
the current behavior to ensure that correctly written HTTP caches are caching
correctly. That performance suffers because of this header is also a conscious
choice, and one we are fully aware of. Cache hits for document lookups are not
very useful, where this matters more is attachments (if they're large) and view
queries (we skip the computation entirely if the view has not changed since you
queried).
Finally, please stop filing duplicates of your issues. If you continue to do so
I will have your account disabled.
> CouchDB 1.6.0 returns wrong Vary
> --------------------------------
>
> Key: COUCHDB-2259
> URL: https://issues.apache.org/jira/browse/COUCHDB-2259
> Project: CouchDB
> Issue Type: Bug
> Security Level: public(Regular issues)
> Components: HTTP Interface
> Reporter: Kaj Nielsen
>
> CouchDB documents are immutable. Even when deleted, a new revision is
> assigned to the document (and the _deleted flag is set).
> As such, HTTP requests for specific document revisions, by use of the
> If-Match header, are cacheable.
> HTTP requests with no revision numbers are not cacheable.
> Therefore, for If-Match requests, the correct caching headers are:
> - Vary: If-Match
> - no Cache-Control header (or a default value, eg. 24hrs)
> And for "non-revisioned" requests, the correct headers are:
> - Vary: If-Match
> - Cache-Control: must-revalidate
> However:
> > GET /db/doc HTTP/1.1
> > Host: localhost:5984
> > If-Match: 167-37f82fdbfdc49d38b1c66815deb1e338
> >
> < HTTP/1.1 200 OK
> < Server: CouchDB/1.6.0 (Erlang OTP/R15B01)
> < ETag: "167-37f82fdbfdc49d38b1c66815deb1e338"
> < Date: Tue, 24 Jun 2014 22:34:20 GMT
> < Content-Type: text/plain; charset=utf-8
> < Content-Length: 649
> < Cache-Control: must-revalidate
> <
> ...
> As seen above, even when requesting a very specific revision of a document,
> CouchDB still requests revalidation with "must-revalidate".
> Thereby making modern HTTP caches unable to take advantage of caching the
> (potentially large) body of HTTP transactions that are perfectly cacheable
> (because the request include If-Match).
> Also, CouchDB incorrectly does not discern the request from a non-revisioned
> request with regards to the "must-revalidate" cache-control header.
> "must-revalidate" should not be set on responses where If-Match is present in
> the request.
--
This message was sent by Atlassian JIRA
(v6.2#6252)
