source: trunk/docs/kernel/mapserver.rst @ 725

.. _kernel-mapserver:
    
Optional MapServer support
==========================

Processing geospatial data using WPS Services is usefull. Publishing their results directly as WMS, WFS or WCS ressources is even more convenient. This is possible since `ZOO-Project 1.3 <http://zoo-project.org>`__ using the **optional MapServer support**. The latter thus allows for automatic publication of WPS Service output as WMS/WFS or WCS using a :ref:`kernel_index` specific internal mechanism which is detailed in this section. 


.. note:: 

  |mapserver| `MapServer <http://mapserver.org>`__ is an open source WMS/WFS/WCS server. Learn more by reading its `documentation <http://mapserver.org/documentation.html>`__.
 

.. |mapserver| image:: ../_static/mapserver.png
       :height: 74px
       :width: 74px
       :scale: 50%
       :alt: MapServer logo


How does it work ?
-------------------------

If a request with ``mimeType=image/png`` is sent to :ref:`kernel_index`, the latter will detect that the *useMapServer* option is set to true an it will automatically:

   * Execute the service using the *<Default>* block definition (these values must be understood by `GDAL <http:/gdal.org>`__)
   * Store the resulting output on disk (in the ``[main]`` > ``dataPath`` directory)
   * Write a `mapfile <http://mapserver.org/mapfile/index.html>`__ (in the ``[main]`` > ``dataPath`` directory) using the `MapServer <http://mapserver.org>`__ C-API (this sets up both WMS and WFS services).

Existing WPS Services source code doesn't need to be modified once the MapServer support is activated. It only takes to edit their respective :ref:`services-zcfg` files accordingly.

.. note:: In case of a vector data source output, both WMS and WFS configuration are included by default in the resulting mapfile.

.. note:: In case of a raster data source output, both WMS and WCS configuration are included by default in the resulting mapfile.

Depending on the requests, ZOO-Kernel is able to return a location header and different request types:

    * ResponseDocument=XXXX@asReference=true

In this case, ZOO-Kernel will return the GetMap/GetFeature/GetCoverage request as KVP in the *href* of the result.

    * ResponseDocument=XXXX@asReference=false

In this case, ZOO-Kernel will return the result of the GetMap/GetFeature/GetCoverage request as KVP of the href used in the previous case.

    * RawDataOutput=XXXX@asReference=true/false

In this case, ZOO-Kernel will return the GetMap/GetFeature/GetCoverage request as KVP in a specific location header, which implies that the browser is supposed to request MapServer directly.

Whatever the default output *mimeType* returned by a WPS service is, it is used if the *useMapserver* option is found at runtime. As an example, if ``<Default>`` and ``<Supported>`` blocks are found in the ZOO Service configuration file as shown bellow, this means that the service returns GML 3.1.0 features by default.

.. code-block:: guess

    <Default>
     mimeType = text/xml
     encoding = UTF-8
     schema = http://schemas.opengis.net/gml/3.1.0/base/feature.xsd
    </Default>
    <Supported>
     mimeType = image/png
     useMapserver = true
    </Supported>

Installation and configuration
------------------------------

Follow the step described bellow in order to activate the ZOO-Project optional MapServer support.

Prerequisites
.............

   * latest `ZOO-Kernel <http://zoo-project.org/trac/browser/trunk/zoo-project/zoo-kernel>`__ trunk version
   * `MapServer <http://mapserver/org>`__ version >= 6.0.1

First download the lastest zoo-kernel by checking out the svn. Use the following command from do the directory where your previously checked out (in this example we will use ``<PREV_SVN_CO>`` to design this directory).

.. code-block:: guess

    cd <PREV_SVN_CO>
    svn checkout http://svn.zoo-project.org/svn/trunk/zoo-kernel zoo-kernel-ms

Then uncompress the MapServer archive (ie. ``mapserver-6.0.1.tar.bz2``) into ``/tmp/zoo-ms-src``, and compile it using the following command:

.. code-block:: guess

     cd /tmp/zoo-ms-src/mapserver-6.0.1
     ./configure --with-ogr=/usr/bin/gdal-config --with-gdal=/usr/bin/gdal-config \
                    --with-proj --with-curl --with-sos --with-wfsclient --with-wmsclient \
                    --with-wcs --with-wfs --with-postgis --with-kml=yes --with-geos \
                    --with-xml --with-xslt --with-threads --with-cairo
     make
     cp mapserv /usr/lib/cgi-bin

Once done, compile ZOO-Kernel with MapServer support from the ``<PREV_SVN_CO>`` directory, using the following command:

.. code-block:: guess

     cd zoo-kernel-ms
     autoconf
     ./configure --with-python --with-mapserver=/tmp/zoo-ms-src/mapserver-6.0.1
     make

You can then copy the new ZOO-Kernel to ``/usr/lib/cgi-bin`` directory, as follow:

.. code-block:: guess

     cp zoo_loader.cgi /usr/lib/cgi-bin


Main configuration file
........................

Open and edit the ``/usr/lib/cgi-bin/main.cfg`` file, by adding the following content in the ``[main]`` section:

.. code-block:: guess

      dataPath = /var/www/temp/
      mapserverAddress=http://localhost/cgi-bin/mapserv

The ``dataPath`` directory is mandatory and must belong to the Apache user.

.. code-block:: guess

     mkdir /var/www/temp/
     chown -r apache:apache /var/www/temp/

A ``symbols.sym`` file is required in this directory. Create it and add the following content in it:

.. code-block:: guess

      SYMBOLSET
      SYMBOL
        NAME "circle"
        TYPE ellipse
        FILLED true
        POINTS
          1 1
        END
      END
      END

.. note::
  Only one symbol definition is required (with any name) for the WMS service output.

The ZOO-Project optional MapServer support is activated at this step. Don't forget to add the ``mapserverAddress`` and  ``msOgcVersion`` parameters to the ``main.cfg`` file in order to  to specify the path to MapServer and the OGC WebService version used by the Services.

.. code-block:: guess
     mapserverAddress=http://localhost/cgi-bin/mapserv.cgi
     msOgcVersion=1.0.0

.. warning::
   ZOO-kernel will segfault (checking ``NULL`` value should correct this behavior) if the ``mapserverAddress`` parameter is not found


Service configuration file
............................

useMapserver
*************

In order to activate the MapServer WMS/WFS/WCS output for a specific service, the ``useMapserver`` parameter must be added to the ``<Default>`` or ``<Supported>`` blocks of the Service `services-zcfg`. If ``useMapserver=true``, this means that the output result of the Service is a GDAL compatible datasource and that you want it to be automatically published by MapServer as WMS,WFS or WCS.

When the useMapserver option is used in a ``<Default>`` or ``<Supported>`` block, then you have to know what are the corresponding mimeType:

   * text/xml: Implies that the output data will be accessible through a WFS GetFeature request (default protocol version 1.1.0)
   * image/tiff: Implies that the output data will be accessible through a WCS GetCoverage request (default protocol version 2.0.0)
   * any other mimeType coupled with useMapserver option: Implies that the output data will be accessible through a WMS GetMap request (default protocol version 1.3.0). You can check the supported output mimeType by sending a GetCapabilities request to MapServer.


You get the same optional parameter ``msOgcVersion`` as for the ``main.cfg``. This will specify that this is the specific protocol version the service want to use (so you may set also locally to service rather than globally).

Styling
*************

The optional ``msStyle`` parameter can also be used to define a custom MapServer style block (used for vector datasource only), as follow:

.. code-block:: guess

     msStyle = STYLE COLOR 125 0 105 OUTLINECOLOR 0 0 0 WIDTH 3 END

If a WPS service outputs a one band raster file, then it is possible to add a ``msClassify`` parameter and set it to ``true`` in the output ComplexData ``<Default>`` or ``<Supported>`` nodes of its ``zcfg`` file. This allows ZOO-Kernel to use its own default style definitions in order to classify the raster using equivalent intervals. 

.. code-block:: guess

     msClassify = ....

Example
**************

An example :ref:`services-zcfg` file configured for the optional MapServer support is shown bellow: 

.. code-block:: guess

    <Default>
     mimeType = text/xml
     encoding = UTF-8
     schema = http://schemas.opengis.net/gml/3.1.0/base/feature.xsd
     useMapserver = true
    </Default>
    <Supported>
     mimeType = image/png
     useMapserver = true
     asReference = true
     msStyle = STYLE COLOR 125 0 105 OUTLINECOLOR 0 0 0 WIDTH 3 END
    </Supported>
    <Supported>
     mimeType = application/vnd.google-earth.kmz
     useMapserver = true
     asReference = true
     msStyle = STYLE COLOR 125 0 105 OUTLINECOLOR 0 0 0 WIDTH 3 END
    </Supported>
    <Supported>
     mimeType = image/tif
     useMapserver = true
     asReference = true
     msClassify = ....
    </Supported>

In this example, the default output ``mimeType`` is ``image/png``, so a WMS GetMap request will be returned, or the resulting ``image/tiff`` will be returned as WCS GetCoverage request.


Test requests
--------------

The optional MapServer support can be tested using any service. The
simple *HelloPy* Service is used in the following example requests.

.. note::
  The following examples require a zip file containing a Shapefile (http://localhost/data/data.zip) and a tif file (http://localhost/data/demo.tif)

Accessing a remote Zipped Shapefile as WFS GetFeatures Request:

.. code-block:: guess

     http://localhost/cgi-bin/zoo_loader.cgi?request=Execute&service=WPS&version=1.0.0&Identifier=HelloPy&DataInputs=a=Reference@xlink:href=http://localhost/data/data.zip&ResponseDocument=Result@asReference=true@mimetype=text/xml

Accessing a remote Zipped Shapefile as WMS GetMap Request:

.. code-block:: guess

     http://localhost/cgi-bin/zoo_loader.cgi?request=Execute&service=WPS&version=1.0.0&Identifier=HelloPy&DataInputs=a=Reference@xlink:href=http://localhost/data/data.zip&ResponseDocument=Result@asReference=true@mimetype=image/png

Accessing a remote tiff as WMS GetMap Request:

.. code-block:: guess

     http://localhost/cgi-bin/zoo_loader.cgi?request=Execute&service=WPS&version=1.0.0&Identifier=HelloPy&DataInputs=a=Reference@xlink:href=http://localhost/data/data.tiff&ResponseDocument=Result@asReference=true@mimetype=image/png

Accessing a remote tiff as WCS GetMap Request:

.. code-block:: guess

     http://localhost/cgi-bin/zoo_loader.cgi?request=Execute&service=WPS&version=1.0.0&Identifier=HelloPy&DataInputs=a=Reference@xlink:href=http://localhost/data/data.tiff&ResponseDocument=Result@asReference=true@mimetype=image/tiff