.. _mapcache_seed:

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Seeder
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:Author: Thomas Bonfort
:Contact: tbonfort at terriscope.fr

Mod-mapcache ships whith an advanced seeding tool, whose main features are:
 * configurable number of seeding threads, to speed up the rendering.
 * ability to reseed tiles older than a certain timestamp
 * ability to seed tiles given a shapefile/ogr datasource

Usage
-----------------------------------------------------------------------------

The seeding utility is named mapcache_seed, and is located in the mapcache/src/
directory of the project


Commandline options
================================================================================

::

   -c [file] : path to the mapcache.xml configuration file that contains the
               tilesets that need to be seeded.
   -t [tileset]: name of the tileset that must be seeded
   -g [grid]: name of the grid that must be seeded (the selected
              tileset must reference the given grid)
   -z minzoom,maxzoom: (optional) start and end zoom levels that must be seeded.
   -e minx,miny,maxx,maxy: (optional) bounding box of the area to seed
   -o (timestamp|now): (optional) only seed tiles that are older than the given value.
                       The value can either be the string "now", or a date formatted
                       like year/month/day hour:minute, eg: "2011/01/31 20:45".
                       (note that a full timestamp should be quoted).
   -n nthreads: number of parallel threads that should be used to request
                tiles from the wms source. The default is 1, but can be set higher
                if the WMS server can withstand parallel requests (as a rule of thumb,
                the value chosen here should never be much higher than the number
                of cpus on the wms server)
   -q: don't print progress messages to the standard output
   -v: print verbose debugging info (if compiled in)
   -D "DIMENSION=VALUE": used to specify which dimension to use if the tileset supports
                         dimensions. Can be used multiple times to set multiple 
                         dimensions, e.g. -D "DIM1=VAL1" -D "DIM2=VAL2"

Optional Commandline options when using OGR/GEOS
================================================================================

At compile time, if ogr and geos where found on the system, the seeder tool
supports additional options to seed only the tiles that cover an arbitrary
geographical area. *Important:* Note that for the time being, the OGR
datasource should be in the same projection as the grid you are seeding, as
there is no automatic reprojection from the datasource projection to the grid
projection.

::

   -d [ogr_datasource]: ogr connection to the spatial source. Consult the OGR
                          documentation for all that is supported. In the simplest case (e.g. a
                           Shapefile), this is just the full filename of the shapefile
   -l [ogr_layer]: (optional) for datasources that contain multiple layers (e.g. postgis, with
                   multiple tables), determines which layer will be used
   -s [ogr_sql]: OGR sql expression that can be applied (see http://www.gdal.org/ogr/ogr_sql.html )
   -w [ogr_where]: sql "where" expression to filter out returned values. This would
                   typically be used to select only the geometry of a given country if the
                   datasource contains all the world contours

Important Note
================================================================================

The seeding utility must be run under the same user account as the
user running the webserver. This is required so the permissions on the tiles
created by the seeder are accessible by the webserver, and conversely so the
seeder has the rights to write files to directories created by the webserver.


A sample seeding session goes like this:

::

  [user@host]$ sudo www-data
  [www-data@host]$ /path/to/mapcache/src/mapcache_seed -c /path/to/www/conf/mapcache.xml [[options]]
  [www-data@host]$ logout
  [user@host]$


Examples
================================================================================

Seed the "osm" tileset with the "g" (google/web-mercator) grid:
::
   
   ./src/mapcache_seed -c mapcache.xml -t osm -g g

Seed levels 0 through 12:
::
   
   ./src/mapcache_seed -c mapcache.xml -t osm -g g -z 0,12

Given a shapefile that contains the world country countours, seed only the
areas that are covered by land (i.e. skip the oceans). Also use 4 request
threads in parallel:
::
   
   ./src/mapcache_seed -c mapcache.xml -t osm -g g -z 0,12 -n 4 -d /path/to/seed.shp

Same as beforehand, but only seed the USA (notice the quote usage, required to
create valid sql with a single-quoted 'US':
::
   
   ./src/mapcache_seed -c mapcache.xml -t osm -g g -z 0,12 -n 4 -d /path/to/seed.shp -w "FIPS_A2='US'"

Reseed levels 0 to 12 (this could also be done by deleting the cache for levels
0 to 12 and doing a classic seed, but doing so this way does not slow down the
access from web clients):
::
   
   ./src/mapcache_seed -c mapcache.xml -t osm -g g -z 0,12 -o now