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MapCache Quickstart
MapCache is a tile server that speeds up access to WMS layers. It can be run as a CGI application under many different web servers, or as an Apache module. OSGeoLive has MapCache installed and configured as an Apache module.
This quick start shows how to add a new WMS layer to a MapCache set-up, display the tile service in an OpenLayers web map, and seed a tile cache from the command line.
Contents
Adding a New Tileset and Displaying in OpenLayers
MapCache is configured using XML files. OSGeoLive includes an example configuration file at ``/usr/local/share/mapcache/mapcache-quickstart.xml``. The example uses the OSGeoLive demo MapServer application of Itasca County in the United States as its source.
In this quick start we will set up tile caching for an additional WMS layer and display the tiles in a simple HTML page containing an OpenLayers map.
First let's open the MapCache configuration file in FeatherPad - a text editor. Open FeatherPad from the command line with elevated permissions, so you can save the file, using System Tools > QTerminal and then running run the command below:
We can see which layers are available in our source WMS server by opening the following link: http://localhost/itasca/?service=wms&request=getcapabilities MapCache is configured to forward on any requests it can't handle, such as GetCapabilities, to MapServer with the rule shown below:
One of the layer names listed in the WMS Capabilities document is ``dlgstln2`` - streams for Itasca county. We will add this as a new tileset to the MapCache service. First we add a ``<source>`` block - this is the configuration to retrieve data from the WMS server. Add the following XML block after the existing ``<source name="lake_source" type="wms">...</source>`` block used for the lakes to ``mapcache-quickstart.xml``:
We use the ``<params>`` block to pass the WMS layer name, and the image format back to the WMS server, along with the MapServer specific ``<map>`` parameter. The URL to the WMS server is in the ``<http>`` block. For documentation on all configuration file elements see the `Configuration Documentation <https://mapserver.org/mapcache/config.html>`_.
We use the ``<params>`` block to pass the WMS layer name, and the image format back to the WMS server, along with the MapServer specific ``<map>`` parameter. The URL to the WMS server is in the ``<http>`` block. For documentation on all configuration file elements see the `Configuration Documentation <https://mapserver.org/mapcache/config.html>`_. Next we will add a ``<tileset>`` block, which defines how the source will be stored and served as tiles. Place the following block after the existing ``<tileset name="lakes">...</tileset>`` block.
We set the grid type to the inbuilt ``GoogleMapsCompatible`` grid used as the default tiling scheme in many web mapping applications. The ``name=streams`` is used by client applications to access the tileset. We are using a disk-based cache (rather than storing tiles in a database or in a cloud environment).
Next we will add a ``<tileset>`` block, which defines how the source will be stored and served as tiles. Place the following block after the existing ``<tileset name="lakes">...</tileset>`` block.
Anytime you modify the MapCache configuration file you need to reload Apache for the changes to come into effect. This can be run from the command line as follows:
You should now be able to access a tile with the following URL: http://localhost/itasca/gmaps/streams@GoogleMapsCompatible/12/987/1433.png
Now let's add the tileset to our OpenLayers map. Open the HTML page using the following command:
Uncomment out the JavaScript code below:
Now refresh the page at http://localhost/mapcache-quickstart/ - you should see the new streams layer being served by MapCache.
As you browse the map you will see the tile cache folders in ``/var/cache/mapcache`` fill with PNG images.
The location and type of the cache is set by the following block in the configuration file:
Adding New Services
You can configure Apache to run as many different MapCache services, each with its own configuration file by editing the ``/etc/apache2/conf-enabled/mapcache.conf`` file. As this requires super user permissions you can open it for editing in FeatherPad by running the command below:
OSGeoLive has two MapCache services, each with an alias and a configuration file. The alias is the URL to use on the server, e.g. http://localhost/mapcache and http://localhost/itasca
To add a new service simply add a new line in the following format, replacing WEB_PATH and PATH_TO_CONFIG_FILE with the relevant parameters:
See the `Apache Module Instructions <https://mapserver.org/mapcache/install.html#apache-module-specific-instructions>`_ for further details on configuring the Apache module.
The Seeder Application
Map tiles are dynamically created when requested by the web server. To speed up request times we can generate tiles using a command line application. This process is known as *seeding*, and the MapCache command line application is ``mapcache_seed``.

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We use the ``<params>`` block to pass the WMS layer name, and the image format back to the WMS server, along with the MapServer specific ``<map>`` parameter. The URL to the WMS server is in the ``<http>`` block. For documentation on all configuration file elements see the `Configuration Documentation <https://mapserver.org/mapcache/config.html>`_.
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