Implements the tilelive API for generating mapnik vector tiles from traditional mapnik datasources.

• xml: a Mapnik XML string that will be used to generate vector tiles.
• base: Optional, basepath for Mapnik map. Defaults to __dirname.

npm install @mapbox/tilelive-bridge

Though tilelive is not a dependency of tilelive-bridge you will want to install it to actually make use of tilelive-bridge through a reasonable API.

var tilelive = require('tilelive');
require('@mapbox/tilelive-bridge').registerProtocols(tilelive);
tilelive.load('bridge:///path/to/file.xml', function(err, source) {
    if (err) throw err;
    // Interface is in XYZ/Google coordinates.
    // Use `y = (1 << z) - 1 - y` to flip TMS coordinates.
    source.getTile(0, 0, 0, function(err, tile, headers) {
        // `err` is an error object when generation failed, otherwise null.
        // `tile` contains the compressed image file as a Buffer
        // `headers` is a hash with HTTP headers for the image.
    });
    // The `.getGrid` is implemented accordingly.
});

You can set a limit to the size of vector tiles created (in bytes) by setting the BRIDGE_MAX_VTILE_BYTES_COMPRESSED=n environment variable. If a tile is generated and larger than the threshold, the process will return Tile >= max allowed size as an error.

If you'd like to get statistics about tiles above a certain byte size (before limiting with the above), you can provide the BRIDGE_LOG_MAX_VTILE_BYTES_COMPRESSED=n environment variable in your tilelive-driven application and this will generate a stats object on you file system named tilelive-bridge-stats.json which includes the average tile size, the maximum tile size, and the number of tiles greater than the threshold set with the environment variable.