Grainstore

Need to simply generate a Mapnik map from a dynamic PostGIS table?

Grainstore is an opinionated Carto MML style store for single PostGIS tables, views or sql queries that outputs Mapnik XML stylesheets.

Map styles can be defined in the Carto map styling language or use default styles. The Carto styles are persisted and Mapnik XML output cached in Redis, making it a good choice for use in map tile servers.

The generated Mapnik XML stylesheet plugs directly into Mapnik or Mapnik based tile server to render a map and interactivity layer.

Grainstore is braindead simple: 1 db + 1 table/query + 1 style = 1 Mapnik XML stylesheet.

Typical use

1. initialise grainstore with PostGIS DB and table name
2. generate Mapnik XML for table with default styles
3. set custom style with carto
4. get carto errors returned if present, else store style
5. generate Mapnik XML with custom style
6. initialise with PostGIS DB, table name and sql query
7. generate Mapnik XML with stored style for table name and sql query

Install

npm install grainstore

Dependencies

• node.js
• npm
• Redis
• libosr (or libgdal)

Additional test dependencies

• libxml2
• libxml2-devel

Examples

var GrainStore = require('grainstore');


// fully default.
var mmls = new GrainStore.MMLStore();
var mmlb = mmls.mml_builder({dbname: 'my_database', table:'my_table'});
mmlb.toXML(function(err, data){
  console.log(data); // => Mapnik XML for your database with default styles
}); 


// custom redis and pg settings.
var mmls = new GrainStore.MMLStore({host:'10.0.0.1'}); 

var render_target = {
  dbname: 'my_db', 
  table:'my_tb', 
  sql:'select * from my_tb where age < 100'
}

// see mml_store.js for more customisation detail 
var mapnik_config = {
  Map: {srid: 4326},
  Datasource: {
    user: "postgres",
    geometry_field: "my_geom"
  }   
}

mmlb = mmls.mml_builder(render_target, mapnik_config);
mmlb.toXML(function(err, data){
  console.log(data); // => Mapnik XML of custom database with default style
}); 



// custom styles.
var mmls = new GrainStore.MMLStore();
var mmlb = mmls.mml_builder({dbname: 'my_database', table:'my_table'});

var my_style = "#my_table{marker-fill: #FF6600;}"

mmlb.setStyle(my_style, function(err, data){
  if err throw err; // any Carto Compile errors
  
  mmlb.toMML(function(err, data){
    console.log(data) // => Carto ready MML
  }); 
  
  mmlb.toXML(function(err, data){
    console.log(data); // => Mapnik XML of database with custom style
  }); 
  
  mmlb.getStyle(function(err, data){
    console.log(data); // => "#my_table{marker-fill: #FF6600;}"
  });
});

For more examples, see the tests.

Tests

To run the tests, from the project root:

> npm install
> npm test

TODO

• multilayer api ;)
• make storage pluggable

to release: npm publish