[OSM-dev] Caching tiles and expiry header

[Moataz Elmasry]

So I did something similar to what you suggested. I copied all headers 
from the original response and changed the headers: "Expires" and  
"Content-Length". I get "|MISS from konqi.openstreetmap.org" in X-Cache, 
where it should have been "HIT"|

Mathieu Arnold wrote:
> +--On 5 juillet 2010 17:27:03 +0200 Moataz Elmasry
> <zaza1851983ml at googlemail.com> wrote:
> | Hello List
> | 
> | I use http://tile.openstreetmap.org/${z}/${x}/${y}.png to display the map
> | in my web application
> | I use a filter mechanism in the servlet, where an expiry header and
> | maximum age headers are added to the image requests, so that they will be
> | cached for a while on the client browser. These are just for common
> | images that the application use like tooltip.png and button.png and
> | such...These are called from the cache just fine
> | 
> | Now to do the same for osm tiles I added a proxy through which the tiles
> | are requested and then expiry headers are added to these tiles, Say
> | http://myapplciation.com/proxy?url=http://tile.openstreetmap.org/${z}/${x
> | }/${y}.png. This is the layer address in OpenLayers.Layer.OSM
> | 
> | An expiry header is added correctly to osm tiles. The problem is that the
> | imagename in the request is different than in the response, so if I'm
> | requesting |http://tile.openstreetmap.org/16/34687/21558.png I get an
> | image called 2736BB16d01.png in my cache. So that by the next call this
> | image won't be fetched from the cache and instead called again from the
> | server and so on.
> | 
> | Is there a way to force the browser to load the images from its cache if
> | available?
>
> Well, you should not create a new expire header, but you should forward the
> expires and etag from the original request, and try to use that etag header
> :
>
> $ curl -I http://tile.openstreetmap.org/16/34687/21558.png
> HTTP/1.0 200 OK
> Date: Mon, 05 Jul 2010 15:27:25 GMT
> Server: Apache/2.2.8 (Ubuntu)
> ETag: "ae22fe7a91ce525e988b2da52f63a4a4"
> Content-Length: 16897
> Cache-Control: max-age=18482
> Expires: Mon, 05 Jul 2010 20:35:27 GMT
> Content-Type: image/png
> Age: 1360
> X-Cache: HIT from konqi.openstreetmap.org
> X-Cache-Lookup: HIT from konqi.openstreetmap.org:3128
> Via: 1.1 konqi.openstreetmap.org:3128 (squid/2.7.STABLE7)
> Connection: close
>
> $ curl -H 'If-None-Match: "ae22fe7a91ce525e988b2da52f63a4a4"' -I
> http://tile.openstreetmap.org/16/34687/21558.png
> HTTP/1.0 304 Not Modified
> Date: Mon, 05 Jul 2010 15:27:25 GMT
> Content-Type: image/png
> Expires: Mon, 05 Jul 2010 20:35:27 GMT
> ETag: "ae22fe7a91ce525e988b2da52f63a4a4"
> Age: 1392
> X-Cache: HIT from konqi.openstreetmap.org
> X-Cache-Lookup: HIT from konqi.openstreetmap.org:3128
> Via: 1.0 konqi.openstreetmap.org:3128 (squid/2.7.STABLE7)
> Connection: close
>
>
> It should be more effective than what you're trying to achieve. (I think.)
>
>
>