CRS:84 Projection results in KeyError while retrieves tiles from Cache.

[U-Tyagi]

It seems its a bug though I am not sure.

Context

Used the config as follows:

<mapproxy.yaml>
layers: 
- name: truemarble
  title: True Marble
  sources: [truemarble_cache]
caches:
  truemarble_cache:
    sources:[truemarble_src]
    format:image/png
    grids:[GLOBAL_WEBMERCATOR, GLOBAL_GEODETIC,GLOBAL_MERCATOR]
sources:
  truemarble_src:
    type:wms
    wms_opts:
      featureinfo:true
      version:1.1.1
    req:
      url:<GeoserverURL>
      transparent:true
      layers:true_marble

Expected Behavior

DEMO app should work with all the SRS populated in ComboBox [Coordinate System]

Actual Behavior

1. http://localhost:8080/demo produces coordinate system combo box with entries [EPSG:3857, EPSG:4326, EPSG:900913, EPSG:4258, CRS:84]. From where last two entries are coming though not specified in section of config.
2. Further Selecting EPSG: 4258 load the wms layer as <srs.py> return best_srs as EPSG:4326 for the selected srs. As the condition .islatlong becomes true.
3. But when I select CRS:84 it results in KEYERROR: as <available_srs> dictionary in <layers.py> doesn't have 'CRS:84' as a key. Though <srs.py> has returned best_srs as CRS:84. Because the condition is true

if target in available_src
    return target

It basically implies:

SRS CRS:84 ('epsg:4326') == SRS EPSG:4326 ('epsg:4326')
return SRS CRS:84 ('epsg:4326')

Possible Fix

Once the condition becomes true return the entry in available_src rather than supplied SRS (query_srs)
I changed the code as follows in srs.py:

if target in available_src
    for avail in available_src:
        if target == avail:
            return avail

It returns the correct entry of SRS to access CacheMap and no more KeyError.

Steps to Reproduce

1. Configure with the mapproxy.yaml as provided above
2. Select CRS:84 in demo app
3. It results in KeyError.

Your Environment

• Version used: 1.15.1
• Python 3.9
• Local development server
• Operating System and version: RHEL 8

Kindly suggest on:

1. How the SRS values are populated in ComboBox of DEMO app.
2. If they are populated why the CRS:84 was resulting in an error and whether the approach to circumvent the error is Okay.

[weskamm]

I will have a look at this in the next days, i also discovered that there appear unintended SRS, so this may need a fix

[landryb]

i think i have a similar issue on a service but with EPSG:900913, using 1.13.0 on debian, the full traceback is:

CRITICAL - mapproxy.wsgiapp - fatal error in service for /service?SERVICE=WMS&VERSION=1.3.0&REQUEST=GetMap&BBOX=275886.9870096099912%2C5507272.485068191774%2C812284.5106800451176%2C5894815.385318184271&CRS=EPSG%3A900913&WIDTH=1715&HEIGHT=1239&LAYERS=ortho&STYLES=&FORMAT=image%2Fjpeg&DPI=96&MAP_RESOLUTION=96&FORMAT_OPTIONS=dpi%3A96
Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/mapproxy/wsgiapp.py", line 141, in __call__
    resp = self.handlers[handler_name].handle(req)
  File "/usr/lib/python3/dist-packages/mapproxy/service/ows.py", line 38, in handle
    return self.services[service].handle(req)
  File "/usr/lib/python3/dist-packages/mapproxy/service/base.py", line 30, in handle
    return handler(parsed_req)
  File "/usr/lib/python3/dist-packages/mapproxy/service/wms.py", line 136, in map
    renderer.render(merger)
  File "/usr/lib/python3/dist-packages/mapproxy/service/wms.py", line 586, in render
    return self._render_capture_source_errors(async_pool, render_layers,
  File "/usr/lib/python3/dist-packages/mapproxy/service/wms.py", line 624, in _render_capture_source_errors
    reraise(ex)
  File "/usr/lib/python3/dist-packages/mapproxy/util/py.py", line 40, in reraise
    raise exc.with_traceback(tb)
  File "/usr/lib/python3/dist-packages/mapproxy/util/async_.py", line 105, in map_each
    yield func(*arg)
  File "/usr/lib/python3/dist-packages/mapproxy/service/wms.py", line 636, in _render_layer
    layer_img = layer.get_map(self.query)
  File "/usr/lib/python3/dist-packages/mapproxy/layer.py", line 347, in get_map
    layer = self._select_layer(query.srs)
  File "/usr/lib/python3/dist-packages/mapproxy/layer.py", line 352, in _select_layer
    return self.srs_map[srs]
KeyError: SRS('EPSG:900913')

the service config for wms has this:

  wms:
    srs: ['EPSG:2154', 'EPSG:4326', 'CRS:84', 'EPSG:4258', 'EPSG:900913', 'EPSG:3857', 'EPSG:3945', 'EPSG:3946']