Flask static_folder hosted on S3

Question

I am trying to reroute all of my /static content to host on Amazon S3. My first thought was to use global config['path'] throughout my jinja templates, but this won't work for external css and js files, plus it is kind of messy. I found the static_folder and static_url_path released in 0.7 and this seems like what I want. However, when I go to http://localhost:8000/static/img/abc.jpg it does not locate the files on S3. Am I using this feature right or is there some other way to do this?

Thanks!

Answer 1

I recently developed a Flask extension to deal with just this situation. It's called Flask-S3, and you can read the documentation for it here.

As an example, here is how you would integrate it into your Flask application:

from flask import Flask
from flask_s3 import FlaskS3

app = Flask(__name__)
app.config['S3_BUCKET_NAME'] = 'mybucketname'
s3 = FlaskS3(app)

You can use the extension to upload your assets to your chosen bucket:

>>> from my_application import app
>>> from flask_s3 import create_all
>>> create_all(app)

Flask-S3 is blueprint aware, and will upload all assets associated with any registered blueprints.

Answer 2

I wish the flask.Flask constructor's static_url_path argument would accept a full URI, but it screams about the path needing a leading slash when you try that. If it accepted it, you could just use url_for after setting static_url_path='http://my_s3_bucket.aws.amazon.com/' or so.

Another possible solution is to use a context processor. I believe this is the cleanest solution, but I don't have much experience with flask. It sure looks clean. Using a context processor, I pull the URL from the environment (I'm using heroku so it's wicked easy to set). Then the context processor makes the static_url variable available in my templates.

In app.py:

# Environment has STATIC_URL='http://my_s3_bucket.aws.amazon.com/'
@app.context_processor
def inject_static_url():
    """
    Inject the variable 'static_url' into the templates. Grab it from
    the environment variable STATIC_URL, or use the default.

    Template variable will always have a trailing slash.

    """
    static_url = os.environ.get('STATIC_URL', app.static_url_path)
    if not static_url.endswith('/'):
        static_url += '/'
    return dict(
        static_url=static_url
    )

In the template:

<link rel="stylesheet" type="text/css" href="{{ static_url }}css/main.css" />

The result

<link rel="stylesheet" type="text/css" href="http://my_s3_bucket.aws.amazon.com/css/main.css" />