[jira] [Resolved] (SVN-4514) HTTP Header "Cache-Control" should be omitted on HEAD URLs

["Ivan Zhakov (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/SVN-4514?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Ivan Zhakov resolved SVN-4514.
------------------------------
       Resolution: Fixed
    Fix Version/s:     (was: 1.10-consider)
                   1.10.0

Should be fixed in r1715551.

> HTTP Header "Cache-Control" should be omitted on HEAD URLs
> ----------------------------------------------------------
>
>                 Key: SVN-4514
>                 URL: https://issues.apache.org/jira/browse/SVN-4514
>             Project: Subversion
>          Issue Type: New Feature
>          Components: mod_dav_svn
>    Affects Versions: trunk
>            Reporter: Subversion Importer
>            Assignee: Ivan Zhakov
>             Fix For: 1.10.0
>
>
> When accessing a Subversion repository via http:// URL using a web browser, mod_dav_svn returns a "Cache-Control: max-age=604800" header (only on files, not on directories).
> This makes the web browser cache the file content for up to a week.
> This makes a lot of sense when a fixed revision was requested, but URLs that imply HEAD, no Cache-Control should be sent. (Note that a Last-Modified header is always sent as well, which should be good enough AFAICT.)
> Example:
> {noformat}
> ▶ wget -Sq -O /dev/null http://svn.apache.org/repos/asf/subversion/trunk/subversion/mod_dav_svn/repos.c
>   HTTP/1.1 200 OK
>   Date: Thu, 10 Jul 2014 15:16:28 GMT
>   Server: Apache/2.2.25 (Unix) DAV/2 mod_wsgi/3.1 Python/2.7.3 SVN/1.8.1 mod_ssl/2.2.25 OpenSSL/1.0.1h
>   Last-Modified: Mon, 23 Jun 2014 20:50:11 GMT
>   ETag: "1604933//subversion/trunk/subversion/mod_dav_svn/repos.c"
>   Cache-Control: max-age=604800
>   Accept-Ranges: bytes
>   Content-Length: 164114
>   Vary: Accept-Encoding
>   Keep-Alive: timeout=15, max=1000
>   Connection: Keep-Alive
>   Content-Type: text/plain; charset=ISO-8859-1
> {noformat}
> (Cache-Control is sent but should not be, as no revision was requested.)
> URLs like these *should* still return a Cache-Control header, as they contain an explicit revision:
>  
> http://svn.apache.org/repos/asf/subversion/trunk/subversion/mod_dav_svn/repos.c?p=1000000
>  
> http://svn.apache.org/repos/asf/subversion/trunk/subversion/mod_dav_svn/repos.c?r=1000000
> URLs that point at directories never include a Cache-Control header. IMHO directories with explicit revisions should also have a Cache-Control header.
> The main point of this issue however: do not confuse web browsers & force users to hard-reload a file URL of HEAD to see recent modifications.
> The header is conditionally hardcoded in subversion/mod_dav_svn/repos.c around line 3050 as:
> {code}
>   /* As version resources don't change, encourage caching. */
>   if ((resource->type == DAV_RESOURCE_TYPE_REGULAR
>        && resource->versioned && !resource->collection)
>       || resource->type == DAV_RESOURCE_TYPE_VERSION)
>     /* Cache resource for one week (specified in seconds). */
>     apr_table_setn(r->headers_out, "Cache-Control", "max-age=604800");
> {code}
> In pseudo code, I think this should become:
> {code}
>   if ((...) && an_explicit_revision_number_was_passed_as_GET_param)
>     apr_table_setn(r->headers_out, "Cache-Control", "max-age=604800");
> {code}
> The GET params are 'r' and 'p'. It seems they don't accept "HEAD", so it might be enough to include the Cache-Control header iff a revision param is non-empty (not having looked through the code too closely yet).
> Original issue reported by *neels*



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