[mapserver-dev] Cache-control in WMS Requests

[Paul Ramsey]

On 3/18/08, Christopher Schmidt <crschmidt at metacarta.com> wrote:

>  > Unfortunately the rest of the headers that affect caching (last
>  > modified, etag, etc) are probably off the table, since they can't be
>  > tracked properly in a dynamic environment.
>
> I'm not sure I agree with this. Perhaps by default you would want such
>  tracking 'off', but certainly one could have a setting which says "use
>  the last modified time of the mapfile for these things", and use the
>  etag/last-modified for that. (Admittedly, it requires more work.)

I was thinking that using the last-modified dates/etags on the source
files would be a clever trick, but it wouldn't work for
database-backed layers, and service backed layers, so it would a
somewhat complex bit of trickery.  Layer-level max_age is tempting,
but also adds complexity with unknown returns.  So, step one,
map-level max_age, and see if anyone uses/likes it.