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

[Kai Krueger]

Jaak Laineste wrote:
> 
>  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 The filtering of what to render (e.g. because they aren't outdated)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rendered tiles on disk and figures out if that tile is outdated or not.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.


Jaak Laineste wrote:
> 
>  How renderd detects whether
> tile should be re-rendered, is it only about date of
> planet-import-complete file, or something else ? Does it matter if I
> tweak layout file?
> 
As mentioned above, it is mod_tile that does the detection and it should
only pass the relevant requests onto renderd.
Tweaking the style sheet will not effect the determination of if a tile is
fresh or not. This only depends on the timestamp of the rendered tile on
disk and the timestamp of the planet-import-complete file. If you want to
force a complete rerender of the tiles due to a change in the style sheet,
you need to update the timestamp of the planet-import-complete file, e.g.
via the command "touch"


Jaak Laineste wrote:
> 
>  I've seen earlier similar issue with live tile rendering -
> renderd/mod_tile tries to rerender tiles which are already rendered
> and as database is never automatically updated, then I know that tiles
> cannot be outdated.
> 
Assuming you planet-import-complete file is in the correct location, it is
readable to mod_tile (apache user) and its timestamp doesn't change, this
shouldn't happen. If it still does, it would be good if you could give some
more information about this to see where things go wrong.

Kai

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