Tegola

Tegola is a high performance vector tile server delivering Mapbox Vector Tiles leveraging PostGIS as the data provider.

Near term goals

• Support for transcoding WKB to MVT.
• Support for /z/x/y web mapping URL scheme.
• Support for PostGIS data provider.

Running Tegola

1. Download the appropriate binary of tegola for your platoform via the release page.
2. Setup your config file and run. Tegola expects a config.toml to be in the same directory as the binary. You can set a different location for the config.toml using a command flag:

./tegola --config=/path/to/config.toml

URL Scheme

Tegola uses the following URL scheme:

/maps/:map_name/:z/:x/:y

• :map_name is the name of the map as defined in the config.toml file.
• :z is the zoom level of the map.
• :x is the row of the tile at the zoom level.
• :y is the column of the tile at the zoom level.

Additional endpoints

/capabilities

Will return a JSON encoded list of the server's configured maps and layers with various attributes. An example response:

{
	"maps": [{
		"name": "zoning",
		"uri": "/maps/zoning",
		"layers": [{
			"name": "landuse",
			"minZoom": 12,
			"maxZoom": 16
		}]
	}]
}

Configuration

The tegola config file uses the TOML format. The following example shows how to configure a PostGIS data provider with two layers. The first layer includes a tablename, geometry_field and an id_field. The second layer uses a custom sql statement instead of the tablename property.

Under the maps section, map layers are associated with dataprovider layers and their min_zoom and max_zoom values are defined. Optionally, custom_tags can be setup which will be encoded into the layer. If the same tags are returned from a data provider, the dataprovider's values will take precidence.

[webserver]
port = ":9090"

# register data providers
[[providers]]
name = "test_postgis"	# provider name is referenced from map layers
type = "postgis"		# the type of data provider. currently only supports postgis
host = "localhost"		# postgis database host
port = 5432				# postgis database port
database = "tegola" 	# postgis database name
user = "tegola"			# postgis database user
password = ""			# postgis database password
srid = 3857             # The default srid for this provider. If not provided it will be WebMercator (3857)

	[[providers.layers]]
	name = "landuse" 					# will be encoded as the layer name in the tile
	tablename = "gis.zoning_base_3857" 	# sql or table_name are required
	geometry_fieldname = "geom"			# geom field. default is geom
	id_fieldname = "gid"				# geom id field. default is gid
	srid = 4326                         # the srid of table's geo data.


	[[providers.layers]]
	name = "roads" 					# will be encoded as the layer name in the tile
	tablename = "gis.zoning_base_3857" 	# sql or table_name are required
	geometry_fieldname = "geom"			# geom field. default is geom
	id_fieldname = "gid"				# geom id field. default is gid
	fields = [ "class", "name" ]        # Additional fields to include in the select statement.
	srid = 3857                         # the srid of table's geo data. Don't need to specify this as it will inherit this from the provider.

	[[providers.layers]]
	name = "rivers" 					# will be encoded as the layer name in the tile
	geometry_fieldname = "geom"			# geom field. default is geom
	id_fieldname = "gid"				# geom id field. default is gid
	# Custom sql to be used for this layer. Note: that the geometery field is wraped
	# in a ST_AsBinary, as tegola only understand wkb.
	sql = """
		SELECT
			gid,
			ST_AsBinary(geom) AS geom
		FROM
			gis.rivers
		WHERE
			geom && !BBOX!
	"""

# maps are made up of layers
[[maps]]
name = "zoning"							# used in the URL to reference this map (/maps/:map_name)

	[[maps.layers]]
	provider_layer = "test_postgis.landuse"	# must match a data provider layer
	min_zoom = 12						# minimum zoom level to include this layer
	max_zoom = 16						# maximum zoom level to include this layer

		[maps.layers.default_tags]		# table of default tags to encode in the tile. SQL statements will override
		class = "park"

	[[maps.layers]]
	provider_layer = "test_postgis.rivers"	# must match a data provider layer
	min_zoom = 10						# minimum zoom level to include this layer
	max_zoom = 18						# maximum zoom level to include this layer

Command flags

Tegola currently supports the following command flags:

• config - Location of config file in TOML format. Can be absolute, relative or remote over http(s).
• port - Port for the webserver to bind to. i.e. :8080
• log-file - Path to write webserver access logs
• log-format - The format that the logger will log with. Available fields:
  • {{.Time}} : The current Date Time in RFC 2822 format.
  • {{.RequestIP}} : The IP address of the the requester.
  • {{.Z}} : The Zoom level.
  • {{.X}} : The X Coordinate.
  • {{.Y}} : The Y Coordinate.

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. Currently support two values:

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

Usage

$ 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 encode a 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

Specifications

• Well Known Binary (WKB)
• Mapbox Vector Tile (MVT) 2.1

License

See license file in repo.