[MapProxy] Issue with use_direct_from_level and WMTS access

[dirk.thalheim at bkg.bund.de]

Hello list,

we have an issue when serving a WMTS layer based upon a cache using the option use_direct_from_level. Basically we want to simulate the WMTS over all levels but not cache the whole levels, as the source is fast enough.

It seems that mapproxy ignores the use_direct_from_level setting, when accessing the layer via WMTS. MapProxy tries to cache the excluded levels. We are seeding the cache offline and the server process has only read access to the cache data. So this results in lots of OSErrors when it tries to cache the new data. When accessing the layer via WMS everything works as expected.

Is this a bug or do we miss something? I could see the behavior on MapProxy Version 1.12.0a-20180212.

Here is an example configuration:

services:
  wms:
    ...
  wmts:
    ...

layers:
  - name: layer
    title: Limited Cache Layer
    sources: [cache]

caches:
  cache:
    grids: [DE_EPSG_25832_ADV]
    sources: [source]
    meta_size: [1, 1]
    meta_buffer: 0
    use_direct_from_level: 8
    cache:
      type: compact
      version: 1
      directory: /path/to/readonly/cache/DE_EPSG_25832_ADV

sources:
 source:
    type: mapnik
    mapfile: "/path/to/mapnik/config.xml"
    layers: ["layer"]
    transparent: true

grids:
  # Grid für WebAtlasDE UTM32 alle Zoomstufen
  DE_EPSG_25832_ADV:
    srs: 'EPSG:25832'
    tile_size: [256, 256]
    res: [4891.96981025128,
          2445.98490512564,
          1222.99245256282,
          611.49622628141,
          305.748113140705,
          152.874056570353,
          76.4370282851763,
          38.2185141425881,
          19.1092570712941,
          9.55462853564703,
          4.77731426782352,
          2.38865713391176,
          1.19432856695588,
          0.597164283477939]
    bbox: [-46133.17, 5048875.268575673, 1206211.101424327, 6301219.54]
    bbox_srs: 'EPSG:25832'
    origin: 'ul'
    stretch_factor: 1.1

Kind regards,

Dirk Thalheim

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