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From "Robert Newson (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (COUCHDB-2259) CouchDB 1.6.0 returns wrong Vary
Date Tue, 24 Jun 2014 22:50:24 GMT

    [ https://issues.apache.org/jira/browse/COUCHDB-2259?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14042806#comment-14042806
] 

Robert Newson commented on COUCHDB-2259:
----------------------------------------

couchdb documents are cacheable but it's important to revalidate with the host server (in
case it's changed). This is still caching, the body can be served from the cache if the host
server returns a 304 response.

> 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.



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