--------- TileCache --------- 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. This implements the WMS-C server recommendation, as defined by http://wiki.osgeo.org/index.php/WMS_Tiling_Client_Recommendation and the Tiled Map Service specification, available at http://wiki.osgeo.org/index.php/Tile_Map_Service_Specification TileCache will run under Python CGI or mod_python. Backend rendering can be powered by remote, or cascading, WMS requests, or by MapServer rendering via python-mapscript. Support for other rendering engines can be added with the implementation of a single function. Caches can be maintained on disk, or via the memcached memory-based LRU caching daemon. TileCache was developed by MetaCarta Labs and released to the public under a BSD license. For updates on tools released by MetaCarta Labs, you can subscribe to the Labs Announce list, available at http://labs.metacarta.com/mailman/listinfo/announce . The TileCache was designed as a companion to OpenLayers, the BSD licensed web mapping interface. For 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 labs@metacarta.com. To set up a TileCache 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 * 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: AddHandler cgi-script .cgi Options +ExecCGI where /var/www/tilecache is the directory resulting from the code extraction. * 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: 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. To set up a TileCache 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 heading: AddHandler python-program .py PythonHandler TileCache.Service PythonOption TileCacheConfig /path/to/tilecache.cfg An example might look like: AddHandler python-program .py PythonHandler TileCache.Service PythonOption TileCacheConfig /var/www/tilecache/tilecache.cfg where /var/www/tilecache is the directory resulting from the code extraction. * 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! To set up a TileCache under a standalone HTTP Server ==================================================== 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. To set up a TileCache 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. To set up a TileCache under IIS =============================== Installing TileCache for use with IIS requires some additional configuration. * Install Python for Windows * Follow "Using Python Scripts with IIS" to setup Python CGI for IIS. http://support.microsoft.com/kb/276494 * Edit metabase.xml to get correct Security Permissions for IIS 6.0. http://blogs.msdn.com/david.wang/archive/2005/04/20/IIS6-CGI-Web-Service-Extension.aspx * Edit tilecache.cgi to specify your configuration file explicitly: svc = Service.load("C:\\TileCache\\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 url -- URL to use when requesting images from a remote WMS server. Required for WMSLayer. OpenLayers with TileCache ========================= 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'. To use TileCache to seed your cache =================================== * Set up the tilecache.cfg if you have not already done so in one of the above configurations * In /var/www/tilecache/TileCache, where /var/www/tilecache is the directory resulting from the code extraction. * The syntax is in the form of; python ./Client.py where: 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 (see the *** note *** above) An example with zoom levels 5 through 12 would be like; /usr/bin/python ./Client.py "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/bin/python ./Client.py "http://example.com/yourdir/tilecache.cgi?" Zip_Codes 0 9 Keeping Your Disk Cache to a Reasonable Size ============================================ 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] 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. 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 -s 500 /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. =30=