Debugging Tegola

Fixing problems in Tegola

Environment Variables

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

TEGOLA_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.


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

Client side

When debugging client side, it’s often helpful 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:


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