Debugging

Environment Variables

The following environment variables can be used for debugging the tegola server:

SQL_DEBUG: specify the type of SQL debug information to output. Supports the following values:

  • LAYER_SQL: print layer SQL as they’re parsed from the config file.
  • EXECUTE_SQL: print SQL that is executed for each tile request and the number of items it returns or an error.
  • LAYER_SQL:EXECUTE_SQL: print LAYER_SQL and EXECUTE_SQL.

Example

$ SQL_DEBUG=LAYER_SQL tegola --config=/path/to/conf.toml

Client side

When debugging client side, it’s often helpful to to see an outline of a tile along with it’s Z/X/Y values. To encode a debug layer into every tile add the query string variable debug=true to the URL template being used to request tiles. For example:

http://localhost:8080/maps/mymap/{z}/{x}/{y}.vector.pbf?debug=true

The requested tile will be encoded with an additional layer with the name value set to debug and include two features:

  • debug_outline: a line feature that traces the border of the tile
  • debug_text: a point feature in the middle of the tile with the following tags:
  • zxy: a string with the Z, X and Y values formatted as: Z:0, X:0, Y:0