Maps

This page describes the technical aspects of deploying Maps service on Wikimedia Foundation infrastructure.

Intro

The maps service consists of Kartotherian - a nodejs service to serve map tiles, Tilerator - a non-public service to prepare vector tiles (data blobs) from OSM database into Cassandra storage, and TileratorUI - an interface to manage Tilerator jobs. There are four servers in the maps group: maps-test200{1,2,3,4}.codfw.wmnet that run Kartotherian (port 6533, NCPU instances), Tilerator (port 6534, half of NCPU instance), TileratorUI (port 6535, 1 instance). Also, there are two Varnish servers in the cache_maps group: cp104{3,4}.eqiad.wmnet.

Monitoring

• Usage dashboard
• Ganglia - Maps Varnish cluster (eqiad)
• Ganglia - Maps cluster (codfw)

Kartotherian

Kartotherian servers map tiles by getting vector data from Cassandra, applying the style to it, and returning raster images. It is also capable of serving a "static image" - a map with a given width/height/scaling/zoom, and can server vector tiles directly for on-the-client rendering (WebGL maps).

• Service configuration template (extends base template)
• Sources configuration

To see the tiles without Varnish cache, connect to Kartotherian using an ssh tunnel, e.g. ssh -L 6533:localhost:6533 maps-test2001.codfw.wmnet and browse to http://localhost:6533

Tilerator

Tilerator is a backend vector tile pre-generation service that picks up jobs from a Redis job que, copying tiles from a Postgres DB, using sql queries into vector tiles stored in Cassandra. Postgres DBs are set up on each of the maps hosts, one master and 3 slaves.

• Service configuration template (extends base template)
• Sources configuration

TileratorUI

TileratorUI is used to add jobs to the Tilerator job queue. Actually, TileratorUI is the same code as Tilerator, but started with a different configuration. Connect to TileratorUI using an ssh tunnel, e.g. ssh -L 6535:localhost:6535 maps-test2001.codfw.wmnet and navigating to http://localhost:6535. There, you can view any style (use set style to change it), or to schedule a job by setting all relevant fields and Control+Clicking the tile you want to schedule.

See full Tilerator documentation for all commands & parameters.

Dynamic Tile Sources

Cassandra

To create a new Cassandra data source, post something like this to the /sources as a text body. Default table name is tiles. If table or keyspace is not there, you have to use createIfMissing parameter.

v2a:
  uri: cassandra://
  params:
    keyspace: v2
    table: tiles2a
    cp: [maps-test2001.codfw.wmnet, maps-test2002.codfw.wmnet, maps-test2003.codfw.wmnet, maps-test2004.codfw.wmnet]
    username: {var: cassandra-user}
    password: {var: cassandra-pswd}
#    repfactor: 4
#    durablewrite: 0
#    createIfMissing: true

Dynamic Layer Generator

To generate just a few layers from database, create a layer filter and a layer mixer:

gentmp:
  uri: bridge://
  xml:
    npm: ["osm-bright-source", "data.xml"]
  xmlSetDataSource:
    if:
      dbname: gis
      host: ""
      type: postgis
    set:
      host: localhost
      user: {var: osmdb-user}
      password: {var: osmdb-pswd}
  xmlLayers: [admin, road]

mixtmp:
  uri: layermixer://
  params:
    sources: [{ref: v2}, {ref: gentmp}]

Once set, POST a job to copy mixtmp into the storage v2 e.g.

src=mixtmp dst=v2 baseZoom=0 fromZoom=5 beforeZoom=6 parts=10

Generating Tiles

Generate all tiles for zooms 0..7, using generator gen, saving into v3 everything including the solid tiles, up to 4 jobs per zoom.

src=gen dst=v3 parts=4 baseZoom=0 fromZoom=0 beforeZoom=8 saveSolid=1

Generated tiles only if they already exist in v2 source, and save them into v3, on zooms 8..15, 60 jobs per zoom.

src=gen dst=v3 parts=60 baseZoom=0 fromZoom=8 beforeZoom=16 sourceId=v2

Bulk Copying

The fastest way to copy a large number of tiles from one source to another is to use a large number of parts and specify saveSolid=true (skips solid tile detection). E.g. to copy all z16 tiles from v2 to v3, use

src=v2 dst=v3 zoom=16 parts=60 saveSolid=true