.. _deployment: Deployment to a production server ================================= As already described in the :ref:`installation` section, no specific deployment procedures are for PyWPS when using flask-based server. But this formula is not intended to be used in a production environment. For production, `Apache httpd `_ or `nginx `_ servers are more advised. PyWPS is runs as a `WSGI `_ application on those servers. PyWPS relies on the `Werkzeug `_ library for this purpose. Deploying an individual PyWPS instance -------------------------------------- PyWPS should be installed in your computer (as per the :ref:`installation` section). As a following step, you can now create several instances of your WPS server. It is advisable for each PyWPS instance to have its own directory, where the WSGI file along with available processes should reside. Therefore create a new directory for the PyWPS instance:: $ sudo mkdir /path/to/pywps/ # create a directory for your processes too $ sudo mkdir /path/to/pywps/processes .. note:: In this configuration example it is assumed that there is only one instance of PyWPS on the server. Each instance is represented by a single `WSGI` script (written in Python), which: 1. Loads the configuration files 2. Serves processes 3. Takes care about maximum number of concurrent processes and similar Creating a PyWPS `WSGI` instance -------------------------------- An example WSGI script is distributed along with PyWPS-Demo service, as described in the :ref:`installation` section. The script is actually straightforward - in fact, it's a just wrapper around the PyWPS server with a list of processes and configuration files passed as arguments. Here is an example of a PyWPS WSGI script:: $ $EDITOR /path/to/pywps/pywps.wsgi .. code-block:: python :linenos: #!/usr/bin/env python3 from pywps.app.Service import Service # processes need to be installed in PYTHON_PATH from processes.sleep import Sleep from processes.ultimate_question import UltimateQuestion from processes.centroids import Centroids from processes.sayhello import SayHello from processes.feature_count import FeatureCount from processes.buffer import Buffer from processes.area import Area processes = [ FeatureCount(), SayHello(), Centroids(), UltimateQuestion(), Sleep(), Buffer(), Area() ] # Service accepts two parameters: # 1 - list of process instances # 2 - list of configuration files application = Service( processes, ['/path/to/pywps/pywps.cfg'] ) .. note:: The WSGI script is assuming that there are already some processes at hand that can be directly included. Also it assumes, that the configuration file already exists - which is not the case yet. The Configuration is described in next chapter (:ref:`configuration`), as well as process creation and deployment (:ref:`process`). Deployment on Apache2 httpd server ---------------------------------- First, the WSGI module must be installed and enabled:: $ sudo apt-get install libapache2-mod-wsgi $ sudo a2enmod wsgi You then can edit your site configuration file (`/etc/apache2/sites-enabled/yoursite.conf`) and add the following:: # PyWPS WSGIDaemonProcess pywps home=/path/to/pywps user=www-data group=www-data processes=2 threads=5 WSGIScriptAlias /pywps /path/to/pywps/pywps.wsgi process-group=pywps WSGIScriptReloading On WSGIProcessGroup pywps WSGIApplicationGroup %{GLOBAL} Require all granted .. note:: `WSGIScriptAlias` points to the `pywps.wsgi` script created before - it will be available under the url http://localhost/pywps .. note:: Please make sure that the `logs`, `workdir`, and `outputpath` directories are writeable to the Apache user. The `outputpath` directory need also be accessible from the URL mentioned in `outputurl` configuration. And of course restart the server:: $ sudo service apache2 restart Deployment on Nginx-Gunicorn ---------------------------- .. note:: We will use Greenunicorn for pyWPS deployment, since it is a very simple to configurate server. For difference between WSGI server consult: `WSGI comparison `_. uWSGU is more popular than gunicorn, best documentation is probably to be found at `Readthedocs `_. We need nginx and gunicorn server:: $ apt install nginx-full $ apt install gunicorn3 It is assumed that PyWPS is installed in your system (if not see: ref:`installation`) and we will used pywps-demo as installation example. First, clonning the pywps-demo example to the root / (you need to be sudoer or root to run the examples):: $ cd / $ git clone https://github.com/geopython/pywps-demo.git Second, preparing the WSGI script for gunicorn. It is necessary that the WSGI script located on the pywps-demo is identified as a python module by gunicorn, this is done by creating a link with .py extention to the wsgi file:: $ cd /pywps-demo/wsgi $ ln -s ./pywps.wsgi ./pywps_app.py Gunicorn can already be tested by setting python path on the command options:: $ gunicorn3 -b 127.0.0.1:8081 --workers $((2*`nproc --all`)) --log-syslog --pythonpath /pywps-demo wsgi.pywps_app:application The command will start a gunicorn instance on the localhost IP and port 8081, logging to systlog (/var/log/syslog), using pywps process folder /pywps-demo/processes and loading module wsgi.pywps_app and object/function application for WSGI. .. note:: Gunicorn uses a prefork model where the master process forks processes (workers) that willl accept incomming connections. The --workers flag sets the number of processes, the default values is 1 but the recomended value is 2 or 4 times the number of CPU cores. Next step is to configure NGINX, by pointing to the WSGI server by changing the location paths of the default site file but editing file /etc/nginx/sites-enabled as follows::: server { listen 80 default_server; listen [::]:80 default_server; server_name _; #better to redirect / to wps application location / { return 301 /wps; } location /wps { # with try_files active there will be problems #try_files $uri $uri/ =404; proxy_set_header Host $host; proxy_redirect off; proxy_set_header X-NginX-Proxy true; proxy_set_header X-Real-IP $remote_addr; proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for; proxy_pass http://127.0.0.1:8081; } } It is likely that part of the proxy configuration is already set on the file /etc/nginx/proxy.conf. Of course the necessatyrestart of nginx :: $ service nginx restart The service will now be available on the IP of the server or localhost :: http://localhost/wps?request=GetCapabilities&service=wps The current gunicorn instance was launched by the user. In a production server it is necessary to set gunicorn as a service On ubuntu 16.04 the systemcltd system requires a service file that will start the gunicorn3 service. The service file (/lib/systemd/system/gunicorn.service) has to be configure as follows:: [Unit] Description=gunicorn3 daemon After=network.target [Service] User=www-data Group=www-data PIDFile=/var/run/gunicorn3.pid Environment=WORKERS=3 ExecStart=/usr/bin/gunicorn3 -b 127.0.0.1:8081 --preload --workers $WORKERS --log-syslog --pythonpath /pywps-demo wsgi.pywps_app:application ExecReload=/bin/kill -s HUP $MAINPID ExecStop=/bin/kill -s TERM $MAINPID [Install] WantedBy=multi-user.target And then enable the service and then reload the systemctl daemon:: $ systemctl enable gunicorn3.service $ systemctl daemon-reload $ systemctl restart gunicorn3.service And to check that everything is ok:: $ systemctl status gunicorn3.service .. note:: Todo NGIX + uWSGI .. _deployment-testing: Testing the deployment of a PyWPS instance ------------------------------------------ .. note:: For the purpose of this documentation, it is assumed that you've installed PyWPS using the `localhost` server domain name. As stated, before, PyWPS should be available at http://localhost/pywps, we now can visit the url (or use `wget`):: # the --content-error parameter makes sure, error response is displayed $ wget --content-error -O - "http://localhost/pywps" The result should be an XML-encoded error message. .. code-block:: xml service The server responded with the :py:class:`pywps.exceptions.MissingParameterValue` exception, telling us that the parameter `service` was not set. This is compliant with the OGC WPS standard, since each request mast have at least the `service` and `request` parameters. We can say for now, that this PyWPS instance is properly deployed on the server, since it returns proper exception report. We now have to configure the instance by editing the `pywps.cfg` file and adding some processes.