NAME¶
tilecache - Cache and serve map tiles
DESCRIPTION¶
TileCache is a BSD licensed tile caching mechanism. The goal is to make it easy
to set up a WMS or TMS frontend to any backend data services you might be
interested in, using a pluggable caching and rendering mechanism.
TileCache was developed by MetaCarta Labs and released to the public under a BSD
license.
The TileCache was designed as a companion to OpenLayers, the BSD licensed web
mapping interface. If you are using TileCache with OpenLayers, please read the
section of this readme which describes how to do so. For additional help with
setting up TileCache for use with OpenLayers, please feel free to stop by
#openlayers, on irc.freenode.net, or to send email to
tilecache@openlayers.org.
RUNNING UNDER CGI¶
- •
- TileCache should have a cgi installed under
/usr/lib/cgi-bin, called tilecache.cgi. This is accessible from
http://yourmachine.example.com/cgi-bin/tilecache.cgi.
- •
- Edit /etc/tilecache.cfg to point the DiskCache to the
location you wish to cache tiles, and the layers to point to the map file
or WMS server you wish to cache.
- •
- Visit:
http://yourmachine.example.com/cgi-bin/tilecache.cgi?LAYERS=basic&SERVICE=WMS&BBOX=-180,-90,0,90
- •
- Or visit:
http://yourmachine.example.com/cgi-bin/tilecache.cgi/1.0.0/basic/0/0/0.png
- •
- If you see a tile, TileCache is working correctly.
RUNNING UNDER MOD_PYTHON¶
- •
- Edit /etc/tilecache.cfg to point the DiskCache to the
location you wish to cache tiles, and the layers to point to the map file
or WMS server you wish to cache.
- •
- Add the following to your Apache configuration:
Alias /tiles /var/lib/python-support/python2.4/tilecache/
<Directory /var/lib/python-support/python2.4/>
SetHandler python-program
PythonHandler TileCache.Service
PythonOption TileCacheConfig /etc/tilecache.cfg
</Directory>
- •
- Visit one of the URLs described above, replacing
tilecache.cgi with tilecache.py
- •
- If you see a tile you have set up your configuration
correctly. Congrats!
RUNNING STANDALONE (UNDER WSGI)¶
TileCache includes standalone HTTP server which uses the WSGI handler. This
implementation depends on
Python Paste , which can be installed via the
python-paste package.
For versions of Python earlier than 2.5, you will also need to install wsgiref:
http://cheeseshop.python.org/pypi/wsgiref
Once you have all the prerequisites installed, simply run:
/usr/sbin/tilecache_http_server
This will start a webserver listening on port 8080 (by default), after which you
should be able to open:
http://yourmachine.example.com:8080/1.0.0/basic/0/0/0.png
to see your first tile.
RUNNING UNDER FASTCGI¶
TileCache includes a fastcgi implementation. In order to use this
implementation, you will need to install flup, available from:
http://trac.saddi.com/flup
This implementation also depends on Python Paste, which can be downloaded via
the python-paste package:
Once you have done this, you can configure your fastcgi server to use
tilecache.fcgi.
Configuring FastCGI is beyond the scope of this documentation.
CONFIGURATION¶
TileCache is configured by a config file, defaulting to tilecache.cfg. There are
several parameters to control TileCache layers that are applicable to all
layers:
- bbox
- The bounding box of the Layer. The resolutions array
defaults to having resolutions which are equal to the bbox divided by 512
(two standard tiles).
- debug
- Whether to send debug output to the error.log. Defaults to
"yes", can be set to "no"
- description
- Layer description, used in some metadata responses. Default
is blank.
- extension
- File extension of the layer. Used to request images from
WMS servers, as well as when writing cache files.
- layers
- A string used to describe the layers. Typically passed
directly to the renderer. The WMSLayer sends this in the HTTP request, and
the MapServerLayer chooses which layer to render based on this string. If
no layer is provided, the layer name is used to fill this property.
- levels
- An integer, describing the number of ´zoom
levels´ or scales to support. Overridden by resolutions, if passed.
- mapfile
- The absolute file location of a mapfile. Required for
MapServer and Mapnik layers.
- maxResolution
- The maximum resolution. If this is set, a resolutions array
is automatically calculated up to a number of levels controlled by the
´levels´ option.
- metaTile
- set to "yes" to turn on metaTiling. This will
request larger tiles, and split them up using the Python Imaging library.
Defaults to "no".
- metaBuffer
- an integer number of pixels to request around the outside
of the rendered tile. This is good to combat edge effects in various map
renderers. Defaults to 10.
- metaSize
- A comma separated pair of integers, which is used to
determine how many tiles should be rendered when using metaTiling. Default
is 5,5.
- resolutions
- Comma separate list of resolutions you want the TileCache
instance to support.
- size
- Comma separated set of integers, describing the
width/height of the tiles. Defaults to 256,256
- srs
- String describing the SRS value. Default is
"EPSG:4326"
- type
- The type of layer. Options are: WMSLayer, MapnikLayer,
MapServerLayer, ImageLayer
- url
- URL to use when requesting images from a remote WMS server.
Required for WMSLayer.
- watermarkImage
- The watermarkImage parameter is assigned on a per-layer
basis. This is a fully qualified path to an image you would like to apply
to each tile. We recommend you use a watermark image the same size as your
tiles. If using the default tile size, you should use a 256x256 image.
NOTE: Python Imaging Library DOES NOT support interlaced images.
- watermarkOpacity
- The watermarkOpacity parameter is assigned on a per-layer
basis. This configures the opacity of the watermark over the tile, it is a
floating point number between 0 and 1. Usage is optional and will
otherwise default.
- extent_type
- Setting this to ´loose´ will allow TileCache to
generate tiles outside the maximum bounding box. Useful for clients that
don´t know when to stop asking for tiles.
- tms_type
- Setting this to "google" will cause tiles to
switch vertical order (that is, following the Google style x/y pattern).
USING TILECACHE WITH OPENLAYERS¶
To run OpenLayers with TileCache the URL passed to the OpenLayers.Layer.WMS
constructor must point to the TileCache script, i.e. tilecache.cgi or
tilecache.py. As an example see the example-cgi.html file included in the
TileCache distribution, under /usr/share/doc/tilecache/examples/.
Note: example-cgi.html assumes TileCache is set up under CGI (see above). If you
set up TileCache under mod_python you´d need to slighly modify
example-cgi.html: the URL passed to the OpenLayers.Layer.WMS constructor must
point to the mod_python script as opposed to the CGI script. Similarly, you
would need to edit this URL if you were to use TileCache with the standalone
HTTP Server or FastCGI.
The most important thing to do is to ensure that the OpenLayers Layer has the
same resolutions and bounding box as your TileCache layer. You can define the
resolutions in OpenLayers via the ´resolutions´ option or the
´maxResolution´ option on the layer. The maxExtent should be defined
to match the bbox parameter of the TileCache layer.
USING TILECACHE WITH MAPSERVER¶
MapServer has a map level metadata option, labelcache_map_edge_buffer, which is
set automatically by TileCache to the metaBuffer plus five when metaTiling is
on, if it is not set in the mapfile.
If you are using MetaTiling, be aware that MapServer generates interlaced PNG
files, which PIL will not read. See
http://mapserver.gis.umn.edu/docs/faq/pil_mapscript on how to resolve this.
SEEDING YOUR TILECACHE¶
The tilecache_seed utility will seed tiles in a cache automatically. You will
need to have TileCache set up in one of the previously described
configurations.
Usage¶
/usr/sbin/tilecache_seed <url> <layer> [<zoom start> <zoom
stop> [<bbox>]]
Arguments¶
- url
- http://example.com/yourdir/tilecache.cgi? or
http://example.com/yourdir/tilecache.py
- layer
- same layer name that is in the tilecache.cfg
- zoom start
- Zoom level to start the process
- zoom end
- Zoom level to end the process
- bbox
- The bounding box to seed
Seeding by center point and radius¶
If called without zoom level arguments, tilecache_seed.py will assume that it
needs to read a list of points and radii from standard input, in the form:
<lat>,<lon>,<radius>
<lat>,<lon>,<radius>
<lat>,<lon>,<radius>
<lat>,<lon>,<radius>
<ctrl + d>
The format of this file is:
- lon
- the position(s) to seed longitude
- lat
- the position(s) to seed latitude
- radius
- the radius around the lon/lat to seed in degrees
Examples¶
An example with zoom levels 5 through 12 would be like;
$ /usr/sbin/tilecache_seed "http://example.com/yourdir/tilecache.cgi?" Zip_Codes 5 12 "-118.12500,31.952162238,-116.015625,34.3071438563"
The bbox can be dropped and defaults to world lonlat(-180,-90,180,90):
$ /usr/sbin/tilecache_seed.py "http://example.com/yourdir/tilecache.cgi?" Zip_Codes 0 9
In center point/radius mode, the zoom level range is not specifiable from the
command-line. An example usage might look like:
$ /usr/sbin/tilecache_seed.py "http://example.com/yourdir/tilecache.cgi?" Zip_Codes
-118.12500,31.952162238,0.05
-121.46327,32.345345645,0.08
<Ctrl+D>
... the seeding will then commence ...
CLEANING YOUR TILECACHE¶
The tilecache_clean utility will remove the least recently accessed tiles from a
cache, down to a specified size.
Usage¶
/usr/sbin/tilecache_clean [options] <cache_location>
Options¶
- --version
- show program´s version number and exit
- -h , --help
- show this help message and exit
- -s SIZE, --size SIZE
- Maximum cache size, in megabytes.
- -e ENTRIES, --entries ENTRIES
- Maximum cache entries. This limits the amount of memory
that will be used to store information about tiles to remove.
Notes¶
The --entries option to tilecache_clean.py is optional, and is used to regulate
how much memory it uses to do its bookkeeping. The default value of 1 million
will hopefully keep RAM utilization under about 100M on a 32-bit x86 Linux
machine. If tilecache_clean.py doesn´t appear to be keeping your disk
cache down to an appropriate size, try upping this value.
tilecache_clean is designed to be run from a cronjob like so:
00 05 * * * /usr/sbin/tilecache_clean.py -s500 /var/www/tilecache
TROUBLESHOOTING¶
Occasionally, for some reason, when using meta tiles, your server may leave
behind lock files. If this happens, there will be files in your cache
directory with the extension ´.lck´. If you are seeing tiles not
render and taking multiple minutes before returning a 500 error, you may be
suffering under a stuck lock.
Removing all files with extension ´.lck´ from the cache directory will
resolve this problem.
SEE ALSO¶
memcached(8)
http://tilecache.org/
http://openlayers.org/
http://wiki.osgeo.org/index.php/WMS_Tiling_Client_Recommendation
http://wiki.osgeo.org/index.php/Tile_Map_Service_Specification
AUTHOR¶
crschmidt@metacarta.com
COPYRIGHT¶
(c) 2006-2007 MetaCarta, Inc. Distributed under the BSD license.