/freemap-mapserver

Map renderrer and HTTP server for mapnik (JsNik) based maps

Primary LanguageJavaScriptApache License 2.0Apache-2.0

Freemap Mapserver

Features

  • Mapnik configuration in Javascript adding all benefits of scripting (preventing repetition, programatic style generation, …)
  • Map tile serving (TMS)
  • PDF output
  • Configurable map pre-rendering
  • On-demand tile rendering (if tile is not rendered yet)
  • Detection of dirty tiles (based on changes reported by imposm3) and rendering scheduling
  • Easy style development and debugging (save and reload)
  • Many features are configurable

Usage

const { startMapserver } = require('freemap-mapserver');
const { mapnikConfig, generateFreemapStyle } = require('./style');
const { legend } = require('./legend');

startMapserver(mapnikConfig, generateFreemapStyle, legend);
  • mapnikConfig - stringified Mapnik XML
  • generateFreemapStyle - function returning stringified Mapnik XML; used for PDF export. Parameters:
    • shading (bool)
    • contours (bool)
    • hikingTrails (bool)
    • bicycleTrails (bool)
    • skiTrails (bool)

Configuration

Your app must use node-config library with configuration of the following structure:

{
  db: {
    type: 'postgis',
    host: 'localhost',
    port: 5432,
    user: 'gis',
    dbname: 'gis',
    password: 'secret',
  },
  dirs: {
    tiles: 'tiles',
    expires: 'expires',
    fonts: 'fonts',
  },
  server: {
    port: 4000,
  },
  workers: {
    // min: 8, commented out = use num of cpus
    // max: 8, commented out = use num of cpus
  },
  forceTileRendering: false, // useful for style development
  dumpXml: false,
  limits: {
    minZoom: 0,
    maxZoom: 19,
    polygon: 'limits.geojson',
    scales: [1, 1.5, 2, 3],
    cleanup: true, // to delete cached tiles out of limits on startup
  },
  prerender: {
    // set to null to disable pre-rendering
    // workers: 8, commented out = use num of cpus
    minZoom: 8,
    maxZoom: 16,
    polygon: 'limits.geojson',
    zoomPrio: [12, 13, 14, 15, 11, 16, 10, 9, 8],
  },
  rerenderOlderThanMs: 0, // use 0 to disable
  renderToPdfConcurrency: 1,
  pngquantOptions: [], // set to null to skip pngquant
  notFoundAsTransparent: true,
  format: {
    extension: 'png',
    mimeType: 'image/png',
    codec: 'png',
  },
  minExpiredBatchSize: 500, // batch size when deleting expired files; set to null to delete without batching,
  expiresZoom: 14, // on which zoom does imposm3 marks tiles as expired,
  prerenderMaxZoom: 14, // we need to know it even in on-demand only instance for creating index files
  // how long to delay rendering a tile when expiring tiles
  // this is to prevent drastical fi i/o slowdown when prerendering eats 100% cpu
  // set to zero to prevent this feature
  prerenderDelayWhenExpiring: 50,
}

Rendering

If prerender is null:

  • On request
    • renders IF tile is missing OR tile is older than rerenderOlderThanMs OR forceTileRendering
    • caches result to tiles dir

If prerender is NOT null:

  • On startup all tiles out of limits are deleted

  • On startup scans all scale-1 tiles within prerender limits and adds tile to Dirty Tiles Register if:

    • scale-1 tile is missing
    • scale-1 tile is older than rerenderOlderThanMs
    • for tile exists a dirty-file

  • On request render tile IF tile is missing OR (is older than rerenderOlderThanMs AND is out of prerender limits)

Dirty tiles marker:

  • reads from expires dir and computes tiles of all zooms from limits
  • every such tile out of prerender limits is deleted
  • if tile exists then it creates its dirty-file and stores it to Dirty Tiles Register

Prerenderer:

  • loops over Dirty Tiles Register
  • for every dirty tile pre-render it
    • TODO if dirty-file render all scales else only missing scales
    • TODO