Deploying the Nominatim Python frontend

The Nominatim can be run as a Python-based ASGI web application. You have the choice between Falcon and Starlette as the ASGI framework.

This section gives a quick overview on how to configure Nginx to serve Nominatim. Please refer to the documentation of Nginx for background information on how to configure it.

Note

Throughout this page, we assume your Nominatim project directory is located in /srv/nominatim-project and you have installed Nominatim using the default installation prefix /usr/local. If you have put it somewhere else, you need to adjust the commands and configuration accordingly.

We further assume that your web server runs as user www-data. Older versions of CentOS may still use the user name apache. You also need to adapt the instructions in this case.

Installing the required packages

The recommended way to deploy a Python ASGI application is to run the ASGI runner uvicorn together with gunicorn HTTP server. We use Falcon here as the web framework.

Create a virtual environment for the Python packages and install the necessary dependencies:

sudo apt install virtualenv
virtualenv /srv/nominatim-venv
/srv/nominatim-venv/bin/pip install SQLAlchemy PyICU psycopg[binary] \
   psycopg2-binary python-dotenv PyYAML falcon uvicorn gunicorn

Setting up Nominatim as a systemd job

Next you need to set up the service that runs the Nominatim frontend. This is easiest done with a systemd job.

First you need to tell systemd to create a socket file to be used by hunicorn. Create the following file /etc/systemd/system/nominatim.socket:

[Unit]
Description=Gunicorn socket for Nominatim

[Socket]
ListenStream=/run/nominatim.sock
SocketUser=www-data

[Install]
WantedBy=multi-user.target

Now you can add the systemd service for Nominatim itself. Create the following file /etc/systemd/system/nominatim.service:

[Unit]
Description=Nominatim running as a gunicorn application
After=network.target
Requires=nominatim.socket

[Service]
Type=simple
Environment="PYTHONPATH=/usr/local/lib/nominatim/lib-python/"
User=www-data
Group=www-data
WorkingDirectory=/srv/nominatim-project
ExecStart=/srv/nominatim-venv/bin/gunicorn -b unix:/run/nominatim.sock -w 4 -k uvicorn.workers.UvicornWorker nominatim.server.falcon.server:run_wsgi
ExecReload=/bin/kill -s HUP $MAINPID
StandardOutput=append:/var/log/gunicorn-nominatim.log
StandardError=inherit
PrivateTmp=true
TimeoutStopSec=5
KillMode=mixed

[Install]
WantedBy=multi-user.target

This sets up gunicorn with 4 workers (-w 4 in ExecStart). Each worker runs its own Python process using NOMINATIM_API_POOL_SIZE connections to the database to serve requests in parallel.

Make the new services known to systemd and start it:

sudo systemctl daemon-reload
sudo systemctl enable nominatim.socket
sudo systemctl start nominatim.socket
sudo systemctl enable nominatim.service
sudo systemctl start nominatim.service

This sets the service up, so that Nominatim is automatically started on reboot.

Configuring nginx

To make the service available to the world, you need to proxy it through nginx. Add the following definition to the default configuration:

upstream nominatim_service {
  server unix:/run/nominatim.sock fail_timeout=0;
}

server {
    listen 80;
    listen [::]:80;

    root /var/www/html;
    index /search;

    location / {
            proxy_set_header Host $http_host;
            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
            proxy_set_header X-Forwarded-Proto $scheme;
            proxy_redirect off;
            proxy_pass http://nominatim_service;
    }
}

Reload nginx with

sudo systemctl reload nginx

and you should be able to see the status of your server under http://localhost/status.