[OSM-dev] mod_tile pre-rendering OSM issues

Corey Dickson cdickson at 1rgs.com
Mon Feb 2 20:03:57 UTC 2015


Using mod_tile/renderd I've got OSM up and running with no issues using
dynamic tile generation.

That being said, I've been working to pre-render zoom levels 0-16 for
another project.

I'm a bit confused about some of the results associated with meta-tile
count.

Pre-rendering tiles seems to work great up until level 15, which is where
tiles count discrepancies start to show up.

Example of level 14 below where the meta-tile count seems appropriate based
on the numbers found here: *http://wiki.openstreetmap.org/wiki/Tile_disk_usage
<http://wiki.openstreetmap.org/wiki/Tile_disk_usage>* (Factor of 64 lower
due to 8x8 meta-tiles)

*Level 14:*
render_old -c /usr/local/etc/renderd.conf -n 4 -t /var/lib/mod_tile -z 14
-Z 14 -s /var/run/renderd/renderd.sock -m default
Rendering old tiles
Planet file updated at Thu Sep 25 21:34:42 2014
Starting 4 rendering threads
Waiting for rendering threads to finish

Total for all tiles rendered
Meta tiles rendered: 0 tiles in 155.28 seconds (0.00 tiles/s)
Total tiles rendered: 0 tiles in 155.28 seconds (0.00 tiles/s)
Total tiles handled: *4194863* tiles in 155.28 seconds (27014.28 tiles/s)

However. once I got to level 15/16 the meta-tile count isn't very
believable, see below:

*Level 15:*
render_old -c /usr/local/etc/renderd.conf -n 4 -t /var/lib/mod_tile -z 15
-Z 15 -s /var/run/renderd/renderd.sock -m default
Rendering old tiles
Planet file updated at Thu Sep 25 21:34:42 2014
Starting 4 rendering threads
Waiting for rendering threads to finish

Total for all tiles rendered
Meta tiles rendered: 0 tiles in 0.09 seconds (0.00 tiles/s)
Total tiles rendered: 0 tiles in 0.09 seconds (0.00 tiles/s)
Total tiles handled: *1665* tiles in 0.09 seconds (18520.58 tiles/s)

*Level 16:*
render_old -c /usr/local/etc/renderd.conf -n 4 -t /var/lib/mod_tile -z 16
-Z 16 -s /var/run/renderd/renderd.sock -m default
Rendering old tiles
Planet file updated at Thu Sep 25 21:34:42 2014
Starting 4 rendering threads
Waiting for rendering threads to finish

Total for all tiles rendered
Meta tiles rendered: 0 tiles in 0.08 seconds (0.00 tiles/s)
Total tiles rendered: 0 tiles in 0.08 seconds (0.00 tiles/s)
Total tiles handled: *1065* tiles in 0.08 seconds (14114.00 tiles/s)

The thing I don't quite understand is if pre-rendering fails for these
levels how is dynamic generation functioning correctly? Based on what I can
see there appears to be no missing data at zoom levels 15/16 when viewing
the data in an OpenLayers style map.

Any insight would be greatly appreciated.

I can provide any additional details if needed.

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