[OSM-dev] Creating Easy Map Embedding

Christopher Schmidt crschmidt at metacarta.com
Mon Oct 22 15:42:25 BST 2007


On Mon, Oct 22, 2007 at 03:01:46PM +0100, David Earl wrote:
> Why don't we create a distributed tile server, so the load can be spread 
> around? Then we do have "infinite resources like Google".

Building a distributed tile server is a lot of work, and not easy. (I
say this having built the innards of a distributed tile cache for
TileCache.)

How many people have the ability to set up and maintain an up to date
copy of the mapnik database? How many people have the server resources to
deploy mapnik, PostGIS, etc. as well as maintaining an up to date copy
of the planet that doesn't fall behind? I think that if you browse
informationfreeway, which uses distributed caches of tiles, you'll see
the benefit this has, but also the drawback, which is that you're
depending on your tile caches to always be available -- when they
aren't, the whole map suffers.

If the answer to 'how many people can bring the same level of resources
to bear on the problem as tile.openstreetmap.org' is 'few', then
distributed tile servers don't get you much, because all the rendering
still has to be done in one place, and (once mod_tile is deployed)
rendering is a lot more work than actually serving tiles. 

In other words: once the mod_tile solution goes out, and a 10x increase
in performance is available, distributed tiles don't actually improve
the situation much/any.

A distributed tile cache is a difficult problem to solve, and it's not
the most important part of the problem here: again, mod_tile will
probably solve the short term performance needs of serving mapnik tiles
from the OpenStreetMap servers. (I could be wrong on this, but this is
the impression I've gotten.) If there is a desire to work on a
highly robust distributed tile serving system, that's great, but it
should be after mod_tile is completed and replaces the current mapnik
tile serving setup.

The more important question -- at least to me -- is "What resources does
OSM want to be providing to users of OSM?" Is 'tiles' one of them, or is
the OSM tile server only a resource designed to be used for OSM.org, and
everything else belongs off site? I don't know how others feel about
this question, and I'd be interested in hearing what others think.

Regards,
-- 
Christopher Schmidt
MetaCarta




More information about the dev mailing list