Add postgis database information to xml generated by carto

General talk
#1

I’m a noob regarding mapnik and GIS systems in general. I have installed the latest mapnik renderer fallowing the information on their website and exported a .pbf file to a local PostGis DB using this command:

osm2pgsql --style ../openstreetmap-carto/openstreetmap-carto.style --create --database gis -U maps -W -H 192.168.220.137 bucharest.osm.pbf

After this I generated a XML style sheet using

carto -a "3.0.0" ../openstreetmap-carto/project.mml > mapnik.xml

Now I would like to use this mapnik.xml in a python script to render a part of the exported map from PostGIS as a test.

#!/usr/bin/env python

from mapnik import *

mapfile = 'mapnik.xml'
map_output = 'mymap33.png'

m = Map(2048, 2048)
load_map(m, mapfile)
bbox=(Box2d( 26.08901,44.420234,26.125488,44.435067))

#m.zoom_to_box(bbox) 
render_to_file(m, map_output)

The problem is that the mapnik.xml has no information about my PostGIS DB (I looked in the file and I saw a lot of queries in element but no host name, user name or password). How do I add more info about my PostGIS DB to this style sheet?

#2

Solved this problem using env variables https://www.postgresql.org/docs/current/static/libpq-envars.html
But now I get some xml parsing errors:

Mapnik LOG> 2017-01-19 05:47:47: Unable to process some data while parsing 'mapnik.xml':
* attribute 'minimum-scale-denominator' with value '750000' at line 0
* attribute 'maximum-scale-denominator' with value '750000' at line 0
* attribute 'maximum-scale-denominator' with value '3000000' at line 0
* attribute 'minimum-scale-denominator' with value '750000' at line 0
* attribute 'maximum-scale-denominator' with value '500000000' at line 0
* attribute 'minimum-scale-denominator' with value '50000000' at line 0
* attribute 'maximum-scale-denominator' with value '6500000' at line 0
* attribute 'minimum-scale-denominator' with value '750000' at line 0
* attribute 'maximum-scale-denominator' with value '750000' at line 0
* attribute 'maximum-scale-denominator' with value '50000' at line 0
* attribute 'maximum-scale-denominator' with value '100000' at line 0
* attribute 'maximum-scale-denominator' with value '3000000' at line 0
* attribute 'minimum-scale-denominator' with value '200000' at line 0
* attribute 'maximum-scale-denominator' with value '50000000' at line 0
* attribute 'maximum-scale-denominator' with value '50000000' at line 0

So far I traced the error to this function in load_map.cpp : void map_parser::find_unused_nodes_recursive(xml_node const& node, std::string & error_message)

I got stuck and don’t know how to continue … any suggestions ?