Folium Override Server

Webserver to re-generate uploaded folium map to use custom URLs.

The service name for this repository is generally abbreviated as fover.

What does this do

This webservice allows any generate folium map done via .save() and ._repr_html_() to have all its external resource URLs replaced with custom URLs, so that the HTML file is transformed to point to custom hosts to load all its external resources. This is useful for hosting and showing maps within non-Internet zone for example.

These URLs to be replaced are split into two sets:

• JS and CSS resource URLs required to display the elements which can be replaced
• Tileserver URL to use custom tileserver-gl map tiles

Simply go to the root path of the service and submit your folium HTML file to

Local demo set-ups

python3 + venv set-up

You will need at least Python 3.6 with venv and pip modules installed.

See https://packaging.python.org/guides/installing-using-pip-and-virtual-environments/#installing-virtualenv for more details on the installation on venv.

Assuming the virtual environment directory to save into is ~/.fover, run the command to create the above directory:

python3 -m venv ~/.fover

Then go into your environment by running source:

source ~/.fover/bin/activate

Then run the following to install the requirements:

python3 -m pip install -r requirements.txt

Finally, you will need to set the required env vars in .env file. The page will still work but the generated HTML file will not make sense with the default env var values.

Finally simply do

gunicorn app:app

In your web browser, go to http://localhost:8000.

If you want to customize the port, binding address or the number of workers to run with, look at the official documentation for more details: https://docs.gunicorn.org/en/stable/run.html.

docker-compose set-up

You will need docker and docker-compose.

Simply run

docker-compose up --build

In your web browser, go to http://localhost:8000.

App config via environment variables

The webserver set-up dynamically picks up all FLASK_APP_ prefixed env vars to be assigned into the app.config. For e.g., if you set the env var FLASK_APP_COMPRESS_LEVEL=9, the webservice would do app.config['COMPRESS_LEVEL'] = 9.

The value to assign can be a JSON string if you need to assign a list, e.g.: FLASK_APP_COMPRESS_ALGORITHM='["gzip"]'.

Currently this webservice has the following packages that require app config set-up:

• Flask-Compress

Versioning

The tag release system here follows this format vX.Y.Z_folium-v0.10.1. ThevX.Y.Z part is the semver for this repository, while the folium-v0.10.1 part is to match the resources that was extracted from folium v0.10.1.

Updating external JSON

The external JSON files required for URL replacement is extracted from https://github.com/dsaidgovsg/folium-resource-server.

The folium version tagged in this repo will fetch the corresponding matching folium version in the above repository.

For convenience, a script to download and update the external JSON files is created at update-external.sh. If the folium version changes for this repository, the script should also be updated accordingly.