[Openstreetmap-dev] Cache the whole world.

[Lars Aronsson]

Erik Johansson wrote:

> Yes squid has an API and the track number is #121 as you discovered. ;-)

(I'm moving this thread back to the dev mailing list, if you don't 
mind.)

Yes, I was fooled at first that the title talks about new tracks 
being added.  This applies to edit mode tiles (with yellow marks).  
But the body text of ticket 121 also mentions view mode tiles 
(with white roads).

(I personally believe that tracks should be drawn as lines, not as 
dots or crosses, and that this should be done by the edit applet 
and not by the tile server.  The edit applet also needs a way to 
color different tracks differently, or only draw select tracks.  
This would remove the need for edit mode tiles all together.)

> The biggest problem is that no one has written a "this lat/lon 
> belongs to these tiles" tool.

This computation surely is part of both the viewer and the edit 
applet.  But with tile URLs ending in e.g. 
BBOX=14.23818,57.84534447446815,14.282125,57.857036747911096
one might raise questions about rounding errors.  There is no 
point in invalidating the cache for a URL where the last decimal 
differs, because that is a different URL.  Perhaps a %.5f format 
should be used for the URLs?  Or something even smarter?

> The other problem with invalidating is that there are lots of zoom
> levels. Why not disabling the Landsat for zoom 16,17,18, or completly?
> I'm not even sure you need landsat for zoom 15.
> 
> Do we really need zoom level 16,17,18? Zoom 16 is a about the same as
> the best from other maping services in Sweden. E.g. moving half a

There are cases where zoom=16 is more useful than zoom=15 in the 
edit applet, e.g. where a bike path runs close to a road.  But I 
have never found any use for zoom=17 or 18.

Editing is only allowed from zoom=14 and up, and we currently draw 
roads only from zoom=11 and up, so there aren't so many levels. 
But one would have to consider that some map updates will touch 
more than one tile at each zoom level.  I have no idea if the 
Squid API allows more than one URL to be invalidated in each call. 
Perhaps one can invalidate the cache for entire areas at once, 
e.g. by specifying wildcard patterns for the tile URLs:  
BBOX=14.3*,57.4*,14.3*,57.5* ?  That would take care of all zoom 
levels too.  Does anybody know?  Google hits indicate that "Squid 
wildcard purge"  is a much desired functionality.


-- 
  Lars Aronsson (lars at aronsson.se)
  Aronsson Datateknik - http://aronsson.se