[OSM-talk] Old data being cached too long

[Tristan Scott]

I've just grabbed a mapnik tile at random, and these are the headers
sent out with it:

Date: Sat, 18 Oct 2008 07:20:05 GMT
Server: Apache/2.2.4 (Ubuntu)
Etag: "cb5563ba81dda2fd9bf27cba5a41164f"
Content-Length: 7149
Cache-Control: max-age=374906
Expires: Wed, 22 Oct 2008 15:28:32 GMT
Content-Type: image/png

Therefore, an ISP's transparent proxy should fetch a new version (or
the same one again) after 374906 seconds, or 4.33 days.

Some ISP's ignore the cache times in their transparent proxies and
therefore should be shouted at. Are any of the tiles you're viewing
older than 4 days? Tiles at home tiles are every day, as I recall, and
therefore three render cycles could be within the timescale?

a T at H headers set:
Date: Sat, 18 Oct 2008 07:27:36 GMT
Server: Apache
Cache-Control: max-age=10800
Last-Modified: Fri, 17 Oct 2008 10:47:20 GMT
Content-Length: 16457
Content-Type: image/png

Which should expire after 3 hours. Notably, this doesn't have a
Expires: header, which means (theoretically) it could get kept longer
as various levels of proxy/cache grab it from each other...
Maybe this would help?

It should be that holding down control and pressing refresh in your
browser should request a new version and not accept cached versions,
but I don't know if this matters to javascript or ISP proxies...

Tristan


2008/10/18 Matias D'Ambrosio <angasule at gmail.com>
>
>  I thought there were some errors with OSM but today visiting a friend we used
> OSM and mapnik was looking just fine, no tiles were old, while at home I get
> a patchwork of new and old, and I have to hit reload a bunch of times to get
> the right one. It's not my cache, btw, I did check for that :-) (Besides, I
> use multiple browsers and they all looked exactly the same.)
>  There is the small chance that OSM is doing something wrong that might cause
> this, but in all likelihood it's my ISP doing business as usual. I know they
> use a transparent proxy, which is quite opaque as this case shows, but not
> being a proxy-knowledgeable person, I don't know exactly what they broke in
> theirs. I see some tiles that are at least two render-cycles old (more than a
> week and a half), and reloading each tile manually is quite annoying, plus
> it's one, if not *the*, largest ISP in Argentina. Could anyone tell me the
> right keywords? What bits to flip? Tomorrow is saturday and I'll be doing
> some work with plenty of dead time for me to call their toll-free number and
> see if I can get someone who can talk beyond the scripted responses (I talked
> with one such person a few years ago), who knows, they might fix it if I
> provide them with the right info.
>
> _______________________________________________
> talk mailing list
> talk at openstreetmap.org
> http://lists.openstreetmap.org/listinfo/talk



--
Tristan Scott BSc(Hons)
Yare Valley Technical Services
www.yvts.co.uk
07837 205829