[OSM-dev] Mapnik's speed rendering slow ?

[Robert (Jamie) Munro]

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Martijn van Oosterhout wrote:
> 
> On Sat, Nov 8, 2008 at 7:12 PM, sylvain letuffe <liste at letuffe.org> wrote:
>>
>> I just can't understand the advantage into putting code in a apache module,
>> instead of "just" doing some rewrite to a python/cgi wrapper that would
>> generate the tiles...
>> Well, after all, why not, for a few % boost ?

You might like tilecache, from the people who made openlayers.

http://tilecache.org/

> AIUI it allows you do to tricks with headers, (If-Modified-Since,
> Expires, etc) in ways that are harder otherwise.

I'm sure you can control headers like that from cgi, mod_python, etc. I
also can't see what can be gained with that sort of thing - just a
default behaviour for If-Modified-Since would be fine, and you can't
tell in advance how long it will be before someone makes a change to
some data in a tile, so you can't usefully set Expires, except maybe to
say that it will be at least an hour.

Robert (Jamie) Munro

P.s. something no one seems to have mentioned on this thread is that
tiles take different amounts of time to render depending on how
complicated they are. Complexity reduces as you zoom in. So it's
sensible to pre-render the first few zoom levels (perhaps to z12), and
render on demand the rest. The map at http://labs.metacarta.com/osm/
works like this, using tilecache, although the JS seems to be broken on
that page.
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