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https://issues.apache.org/jira/browse/COUCHDB-257?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Christopher Lenz reopened COUCHDB-257:
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Oops, turns out I got this wrong. As Curt explains on the mailing list, adding
an Expires header set to the past, in combination with the "Cache-Control:
must-revalidate" header we're already sending, just forces the user agent to
not apply any heuristics to determine freshness and always revalidate with the
server. This is the behavior we want.
Furthermore, according to Curt, max-age=0 or Expires=Date is insufficient
because at least with some user agents there's a one second window where you
could still get the cached entity without revalidation.
In light of this I retract my objection. Sorry for the noise!
> HTTP caching headers don't provide expected behaviour
> -----------------------------------------------------
>
> Key: COUCHDB-257
> URL: https://issues.apache.org/jira/browse/COUCHDB-257
> Project: CouchDB
> Issue Type: Bug
> Components: HTTP Interface
> Affects Versions: 0.8.1, 0.9
> Environment: Server: Ubuntu Hardy on x86. Client: Windows XP (32-bit).
> Reporter: Vinay Sajip
> Priority: Minor
> Attachments: caching-header-patch.diff, expires.patch
>
>
> The HTTP caching headers currently put out cause IE (for example) to not
> display information correctly in Futon. It's easy to reproduce: I open
> windows in Firefox and IE simultaneously, do an update using Firefox (e.g.
> add a new document) and refresh the IE window. The updated document count is
> not shown. If I clear the browser cache and try again, the updated
> information is displayed. The HTTP header put out is
> Cache-Control: must-revalidate
> which seems to me insufficient - for IE, at least. Is there way of
> configuring these headers, to for example
> Cache-Control: no-cache
> Pragma: no-cache
> Expires: some date in the past, or the same value as the Date: header
> Christopher Lenz has said about this that "This is due to extra-aggressive
> (and against the HTTP spec) caching that IE does on XMLHTTPRequests. A
> patch would need to do user agent sniffing to conditionally add the "cache:
> false" parameter to the jQuery ajax() invocations in jquery.couch.js (and
> maybe elsewhere). I wouldn't want to add this for all user agents, as it
> basically circumvents any caching for AJAX requests (even for
> not-craptastically-broken implementations), and thus would add quite a bit
> of unnecessary overhead."
> To this, I would comment that I don't believe a patch to the client-side code
> in Futon would be sufficient. There are other clients out there, some of
> which will be on Windows and so by default use the (acknowledgely broken)
> Microsoft stack. In my view it is more important to err on the side of
> correctness than performance - so I believe the headers generated server-side
> need to change, as well as perhaps Futon client-side changes.
> I note that handle_uuids_req in couch_httpd_misc_handlers.erl uses the
> no-cache/Expires scheme I mention.
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