Problem with compositing two mbtiles

[t2wu]

This code tries to composite tiles from two mbtiles and make into a composite:

import logging
from landez import MBTilesBuilder, TilesManager

logging.basicConfig(level=logging.DEBUG)

mb = MBTilesBuilder(filepath="composite_z12_15.mbtiles", mbtiles_file="OSMBrightZ12_15_label_only.mbtiles")  # base layer
overlay = TilesManager(mbtiles_file="watercolor_z12_15.mbtiles")
# if no coverage the bottom layer, but I need this to avoiding running into another landez bug
mb.add_coverage(bbox=(-122.1099,37.4531,-121.8768,37.6107), zoomlevels=range(12,16)) # 12 to 15
mb.add_layer(overlay)
mb.run()

This runs into the error of:

DEBUG:landez.sources:Execute query 'SELECT tile_data FROM tiles WHERE zoom_level=? AND tile_column=? AND tile_row=?;' ((15, 5284, 20081),)
Traceback (most recent call last):
File "./composite.py", line 13, in
mb.run()
File "/usr/local/lib/python2.7/dist-packages/landez-2.0.3.dev0-py2.7.egg/landez/tiles.py", line 288, in run
self._gather((z, x, y))
File "/usr/local/lib/python2.7/dist-packages/landez-2.0.3.dev0-py2.7.egg/landez/tiles.py", line 322, in gather
tilecontent = self.tile((z, x, y))
File "/usr/local/lib/python2.7/dist-packages/landez-2.0.3.dev0-py2.7.egg/landez/tiles.py", line 155, in tile
output = self.reader.tile(z, x, y)
File "/usr/local/lib/python2.7/dist-packages/landez-2.0.3.dev0-py2.7.egg/landez/sources.py", line 106, in tile
raise ExtractionError(("Could not extract tile %s from %s") % ((z, x, y), self.filename))
landez.sources.ExtractionError: Could not extract tile (15, 5284, 12686) from OSMBrightZ12_15_label_only.mbtiles

Where as my previous code (which I mistakenly written with two overlays) ran fine:

logging.basicConfig(level=logging.DEBUG)
mb = MBTilesBuilder(filepath="composite_z12_15.mbtiles")
overlay = TilesManager(mbtiles_file="OSMBrightZ12_15_label_only.mbtiles")
overlay2 = TilesManager(mbtiles_file="watercolor_z12_15.mbtiles")

# if no coverage the bottom layer, but I need this to avoiding running into another landez bug
mb.add_coverage(bbox=(-122.1099,37.4531,-121.8768,37.6107), zoomlevels=range(12,16)) # 12 to 15

mb.add_layer(overlay2)
mb.add_layer(overlay)
mb.run()

I think the first code is grabbing the wrong tile number.

[leplatrem]

This would basically mean that the coverage you specify is too large or covers unavailable zoom levels.

The explanation about the successful run when using overlays is here :
https://github.com/makinacorpus/landez/blob/master/landez/tiles.py#L178-183

For overlays, we only show a warning if the tile is missing, whereas we raise errors for the base layer.

[t2wu]

Thanks. That explains it. That's probably because my add_coverage() call is spanning an area bigger than the tiles are? But that would be weird, giving that the same bbox is used for the base layer which I obtained from TileMill, and the overlay which I obtained using Landez connecting to Stamen's watercolor tiles.

What's the default behavior suppose to be if I don't supply any coverage area?
Right now it would cause exception to throw (please mind that the line number might be different from the trunk)

DEBUG:landez.tiles:Clean-up /tmp/landez/composite_z12_15_2
Traceback (most recent call last):
  File "./composite.py", line 13, in <module>
    mb.run()
  File "/usr/local/lib/python2.7/dist-packages/landez-2.0.3.dev0-py2.7.egg/landez/tiles.py", line 271, in run
    metadata = bottomlayer.reader.metadata()
AttributeError: 'tuple' object has no attribute 'reader'