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deprecated-single-page-apps-in-same-container.md

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Deprecated technique for SPAs in a single container

Notice: this technique is deprecated, as it can create several issues with modern frontend frameworks. For the details and better alternatives, read the notes in the main README.

This section explains how to configure the image to serve the contents of /static/index.html directly when the browser requests /.

This is specially helpful (and efficient) if you are building a Single-Page Application (SPA) with JavaScript ( Vue, React, Angular, etc.) and you want the index.html to be served directly, without modifications by Python or Jinja2 templates. And you want to use Flask mainly as an API / back end for your SPA front end.

Note: You can download the example project example-flask-python3.7-index.zip and use it as the template for your project in the Examples section above.

Or you may follow the instructions to build your project from scratch (it's very similar to the procedure above):

  • Go to your project directory
  • Create a Dockerfile with:
FROM tiangolo/uwsgi-nginx-flask:python3.7

ENV STATIC_INDEX 1

COPY ./app /app
  • Create an app directory and enter in it
  • Create a main.py file (it should be named like that and should be in your app directory) with:
import os
from flask import Flask, send_file
app = Flask(__name__)


@app.route("/hello")
def hello():
    return "Hello World from Flask"


@app.route("/")
def main():
    index_path = os.path.join(app.static_folder, 'index.html')
    return send_file(index_path)


# Everything not declared before (not a Flask route / API endpoint)...
@app.route('/<path:path>')
def route_frontend(path):
    # ...could be a static file needed by the front end that
    # doesn't use the `static` path (like in `<script src="bundle.js">`)
    file_path = os.path.join(app.static_folder, path)
    if os.path.isfile(file_path):
        return send_file(file_path)
    # ...or should be handled by the SPA's "router" in front end
    else:
        index_path = os.path.join(app.static_folder, 'index.html')
        return send_file(index_path)


if __name__ == "__main__":
    # Only for debugging while developing
    app.run(host='0.0.0.0', debug=True, port=80)

the main application object should be named app (in the code) as in this example.

Note: The section with the main() function is for debugging purposes. To learn more, read the Advanced instructions below.

  • Make sure you have an index.html file in ./app/static/index.html, for example with:
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Index</title>
</head>
<body>
<h1>Hello World from HTML</h1>
</body>
</html>
  • You should now have a directory structure like:
.
├── app
│   ├── main.py
│   └── static
│       └── index.html
└── Dockerfile
  • Go to the project directory (in where your Dockerfile is, containing your app directory)
  • Build your Flask image:
docker build -t myimage .
  • Run a container based on your image:
docker run -d --name mycontainer -p 80:80 myimage

...and you have an optimized Flask server in a Docker container. Also optimized to serve your main static index.html page.

Note: As your index.html file will be served from / and from /static/index.html, it would be better to have absolute paths in the links to other files in the static directory from your index.html file. As in /static/css/styles.css instead of relative paths as in ./css/styles.css. But still, above you added code in your main.py to handle that too, just in case.