[OSM-dev] mod_tile / render_list re-renders existing tiles without apparent need

[Jaak Laineste]

>>  I do not have diff update for my osm2pgsql database, just to make
>> renderd happy I created /var/lib/mod_tile/planet-import-complete file
>> with yesterdays date and started to prerender tiles with ./render_list
>> -m default -a -z 0 -Z 10
>>
>>  But now I noticed that when I rerun the command then it always
>> re-renders also already existent tiles.
>>
> Indeed render list renders all tiles you specify in the list independent of
> their age.
> The rendering daemon (renderd or tirex) render everything that they get
> handed. The filtering of what to render (e.g. because they aren't outdated)
> happens in the calling program e.g mod_tile or render_list. What you are
> probably looking for is the program render_old. It gos through all the
> rendered tiles on disk and figures out if that tile is outdated or not. If
> it is, it submits it for re-rendering. If it is fresh, it will just ignore
> the tile.

Mod_tile includes bunch of render_x scripts with very little
explanation or list of command parameters, maybe I just picked wrong
one. What I'm looking for is effective prerendering for globe on zoom
0-9 (or so). It is days-long process, so there can be need to stop it
and continue. For now I understood that:

a) Render_old probably does not fit for initial pre-rendering, as I do
not have yet any tile file. It could be good after planet updates.
b) Render_list just forces rerendering of everything (I use --all
parameter), even if tile already exists. It would work for initial
rendering if you are doing it really from zero and with single run.
But if I've done zooms 0-3 and some of 4, then need to restart machine
and then continue, then I need somehow find out what was the last zoom
and re-render from this at least.
c) render_expired sounds closest to my need by description, but I do
not have specific list and this has no --all parameter.

 It sounds like too standard problem for me to start new scripting.

-- 
Jaak