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From Mark Nottingham <>
Subject Re: mod_cache: serving stale content during outages
Date Wed, 20 Oct 2010 00:40:16 GMT
FYI, while you're doing this it might be interesting to make it explicitly controllable by
the origin:


On 12/10/2010, at 9:43 AM, Graham Leggett wrote:

> Hi all,
> RFC2616 allows us to serve stale content during outages:
>    /* RFC2616 13.8 Errors or Incomplete Response Cache Behavior:
>     * If a cache receives a 5xx response while attempting to revalidate an
>     * entry, it MAY either forward this response to the requesting client,
>     * or act as if the server failed to respond. In the latter case, it MAY
>     * return a previously received response unless the cached entry
>     * includes the "must-revalidate" cache-control directive (see section
>     * 14.9).
>     */
> The next patch teaches mod_cache how to optionally serve stale content should a backend
be responding with 5xx errors, as per the RFC above.
> In order to make this possible, the cache_out_filter needed to be cleaned up so that
it cleanly discarded data before the EOS bucket (instead of ignoring it, as before). The cache_status
hook needed to be updated so that r->err_headers_out could be passed to it.
> Regards,
> Graham
> --

Mark Nottingham

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