=================
Getting Started
=================
-------------------------
Cache and serve map tiles
-------------------------
:Author: labs@metacarta.com
:Copyright: (c) 2006-2010 TileCache Contributors
Distributed under the BSD license.
:Version: 2.11
:Manual section: 8
:Manual group: GIS Utilities
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.
Installing TileCache
====================
Generally, installing TileCache is as simple as downloading a source
distribution and unpacking it. For installation systemwide, you can also use
the Python Package Index (aka pypi or Cheeseshop) to install TileCache. Simply
type easy_install TileCache. Once this is done, you will need to install the
TileCache configuration file. A tool to do this is installed, called
tilecache_install_config.py. A full installation likely looks like::
$ sudo easy_install TileCache
...
Installed
/usr/lib/python2.5/site-packages/TileCache-2.10-py2.5.egg
$ sudo tilecache_install_config.py
Successfully copied file
/usr/lib/python2.5/site-packages/TileCache-2.10-py2.5.egg/TileCache/tilecache.cfg
to /etc/tilecache.cfg.
TileCache is also available as a Debian package from the TileCache homepage.
This Debian package is designed to install on Debian etch releases or later.
This Debian package should install on Ubuntu Feisty or Gutsy.
Running Under CGI
=================
* Extract the code to some web directory (e.g. in /var/www).
* Edit 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. On Debian, this file is in /etc/tilecache.cfg
by default.
* Permit CGI execution in the TileCache directory.
For example, if TileCache is to be run with Apache, the
following must be added in your Apache configuration,
where /var/www/tilecache is the directory resulting from
the code extraction. On Debian, this is typically /usr/lib/cgi-bin.
::
<Directory /var/www/tilecache>
AddHandler cgi-script .cgi
Options +ExecCGI
</Directory>
* Visit:
http://example.com/yourdir/tilecache.cgi?LAYERS=basic&SERVICE=WMS
&VERSION=1.1.1&REQUEST=GetMap&SRS=EPSG:4326&BBOX=-180,-90,0,90
&WIDTH=256&HEIGHT=256
* Or visit:
http://example.com/yourdir/tilecache.cgi/1.0.0/basic/0/0/0.png
* If you see a tile you have set up your configuration correctly. Congrats!
Non-standard Python Location
----------------------------
If your Python is not at /usr/bin/python on your system, you will need to
change the first line of tilecache.cgi to reference the location of your Python
binary. A common example is:
::
#!/usr/local/bin/python
Under Apache, you might see an error message like:
::
[Wed Mar 14 19:55:30 2007] [error] [client 127.0.0.1] (2)No such file or
directory: exec of '/www/tilecache.cgi' failed
to indicate this problem.
You can typically locate where Python is installed on your system via the
command which python.
Windows users: If you are using Windows, you should change the first line
of tilecache.cgi to read:
::
#!C:/Python/python.exe -u
C:/Python should match the location Python is installed under on your
system. In Python 2.5, this location is C:/Python25 by default.
Running Under mod_python
========================
* Extract the code to some web directory (e.g. /var/www).
* Edit 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, under a <Directory> heading:
::
AddHandler python-program .py
PythonHandler TileCache.Service
PythonOption TileCacheConfig /path/to/tilecache.cfg
* An example might look like:
::
<Directory /var/www/tilecache/>
AddHandler python-program .py
PythonHandler TileCache.Service
PythonOption TileCacheConfig /var/www/tilecache/tilecache.cfg
</Directory>
* In this example, /var/www/tilecache is the directory resulting from
the code extraction. If you've installed this from a Debian package, the
location of your .cfg file is probably /etc/tilecache.cfg.
* Edit tilecache.cfg to point to the location of your 'Layers' directory,
as demonstrated inside the default tilecache.cfg.
* 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 as of version 1.4 comes with a standalone HTTP server which uses
the WSGI handler. This implementation depends on *Python Paste*, which can be
downloaded from:
http://cheeseshop.python.org/pypi/Paste
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:
::
python tilecache_http_server.py
This will start a webserver listening on port 8080, after which you should
be able to open:
::
http://hostname:8080/1.0.0/basic/0/0/0.png
to see your first tile.
Running Under FastCGI
=====================
TileCache as of version 1.4 comes with 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
from:
http://cheeseshop.python.org/pypi/Paste
Once you have done this, you can configure your fastcgi server to use
tilecache.fcgi.
Configuring FastCGI is beyond the scope of this documentation.
Running Under Apache + mod_wsgi 2
=================================
This note is meant to be a technical outline, not a set of directions.
Assuming you have installed TileCache to, say, /var/www/tilecache, the
following has been known to work in an Apache .conf:
<Directory /var/www/tilecache>
Order allow,deny
Allow from all
</Directory>
WSGIScriptAlias /tile /var/www/tilecache/TileCache/Service.py
WSGICallableObject wsgiApp
WSGIDaemonProcess TileCache processes=2 threads=15 python-path=/var/www/tilecache/TileCache:/var/www/tilecache
WSGIProcessGroup TileCache
The `python-path` bit in the `WSGIDaemonProcess` parameter appears to be
necessary, because of the way that mod_wsgi sets up the Python path.
Running Under IIS
=================
Installing TileCache for use with IIS requires some additional configuration.
A nice document for setting up TileCache on IIS is available from Vish's
weblog: http://viswaug.wordpress.com/2008/02/03/setting-up-tilecache-on-iis/ .
Running Standalone with PasteScript and CherryPy
================================================
One component of the CherryPy web framework is a pure Python, fast,
HTTP/1.1-compliant, WSGI thread-pooled webserver.
To deploy Tilecache using this option you have to:
* Install prerequisites:
easy_install PasteScript
easy_install CherryPy
* Create a deployment config file specifying the http server and the
application with options. The format of the configuration file is
documented here: http://pythonpaste.org/deploy/#the-config-file
Example configuration file follows. Copy the lines into tc.ini, tweak
the tilecache_config variable, run paster serve tc.ini and enjoy at
http://127.0.0.1:5000/tc
::
[server:main]
#tested with Paste#http and PasteScript#wsgiutils, PasteScript#twisted
also possible after installing dependencies
use = egg:PasteScript#cherrypy
host = 127.0.0.1
port = 5000
[composite:main]
use = egg:Paste#urlmap
/tc = tilecache1
[app:tilecache1]
use = egg:TileCache
tilecache_config = tilecache.cfg
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 seperated pair of integers, which is used to
determine how many tiles should be rendered when using
metaTiling. Default is 5,5.
resolutions
Comma seperate list of resolutions you want the TileCache
instance to support.
size
Comma seperated 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 index.html file included in the TileCache
distribution.
Note: index.html assumes TileCache is set up under CGI (see above). If you set
up TileCache under mod_python you'd need to slighly modify index.html: the URL
passed to the OpenLayers.Layer.WMS constructor must point to the mod_python
script as opposed to the CGI script, so replace tilecache.cgi with
tilecache.py. 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.
If you are using TileCache for overlays, you should set the 'reproject' option
on the layer to 'false'.
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://www.mapserver.org/faq.html#why-doesn-t-pil-python-imaging-library-open-my-pngs on how to resolve this.
Using With Python-Mapscript
===========================
Several users have reported cases where large mapfiles combined with
python-mapscript has caused memory leaks, which eventually lead to
segfaults. If you are having problems with Apache/TileCache segfaults
when using python-mapscript, then you should switch to using a WMS
Layer instead of a MapServer Layer.
Seeding your TileCache
======================
The tilecache_seed.py utility will seed tiles in a cache automatically. You will
need to have TileCache set up in one of the previously described configurations.
Usage
-----
tilecache_seed.py [options] <layer> [<zoom start> <zoom stop>]
Options
-------
--version show program's version number and exit
-h, --help show this help message and exit
-f, --force force recreation of tiles even if they are already in
cache
-b BBOX, --bbox=BBOX restrict to specified bounding box
-p PADDING, --pading=PADDING
extra margin tiles to seed around target area.
Defaults to 0 (some edge tiles might be missing).
A value of 1 ensures all tiles will be created, but
some tiles may be wholly outside your bbox
Arguments
---------
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
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 and ~2 extra tiles around each zoom level would be like:
::
$ tilecache_seed.py Zip_Codes 5 12 "-118.12500,31.952162238,-116.015625,34.3071438563" 2
The bbox can be dropped and defaults to world lonlat(-180,-90,180,90):
::
$ tilecache_seed.py 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:
::
$ tilecache_seed.py 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.py utility will remove the least recently accessed
tiles from a cache, down to a specified size.
Usage
-----
tilecache_clean.py [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.py is designed to be run from a cronjob like so:
::
00 05 * * * /usr/local/bin/tilecache_clean.py -s500 /var/www/tilecache
Note that, on non-POSIX operating systems (particularly Windows),
tilecache_clean.py measures file sizes, and not disk usage. Because most
filesystems use entire file blocks for files smaller than a block, running du
-s or similar on your disk cache after a cleaning may still return a total
cache size larger than you expect.
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