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https://issues.apache.org/jira/browse/COUCHDB-2261?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Joan Touzet closed COUCHDB-2261.
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Resolution: Duplicate
Duplicate of COUCHDB-2260
> CouchDB 1.6.0 returns wrong Cache-Control header
> ------------------------------------------------
>
> Key: COUCHDB-2261
> URL: https://issues.apache.org/jira/browse/COUCHDB-2261
> Project: CouchDB
> Issue Type: Bug
> Security Level: public(Regular issues)
> Components: HTTP Interface
> Reporter: Kaj Nielsen
>
> CouchDB returns "must-revalidate" in all responses.
> This does not mean what you think it means.
> Modern HTTP caches will happily return cached copies of "must-revalidate"
> items without consulting the backend server.
> According to the RFC:
> ================================================
> Section 14.9.4 of HTTP/1.1:
> When the must-revalidate directive is present in a response received by a
> cache, that cache MUST NOT use the entry after it becomes stale to respond to
> a subsequent request without first revalidating it with the origin server
> Section 14.8 of HTTP/1.1:
> If the response includes the "must-revalidate" cache-control directive, the
> cache MAY use that response in replying to a subsequent request. But if the
> response is stale, all caches MUST first revalidate it with the origin
> server...
> ================================================
> Meaning that the cache may serve the item without revalidation as long as the
> response is not stale yet.
> When is the response stale?
> Regarding staleness, see for example RFC5861:
> ==============================================
> A response containing:
> Cache-Control: max-age=600, ...
> indicates that it is fresh for 600 seconds
> ==============================================
> Meaning that the content goes stale after the max-age expires.
> Since CouchDB does not set a max-age, the cache may assume that the content
> does not go stale, and thus that must-revalidate is irrelevant.
> Which is exactly what Varnish does when you stick it in front of CouchDB.
> Correct solution is to set either:
> * Cache-Control: max-age=0, must-revalidate
> Or:
> * Cache-Control: no-cache
> The latter meaning that the cache must also refresh on each request (but is
> free to use conditional GETs if it wishes) - see RFC.
> See also:
> https://stackoverflow.com/questions/7573466/is-cache-controlmust-revalidate-obliging-to-validate-all-requests-or-just-the
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