Submit static files from CDN, not to flask in production

Question

In my Flask application, I serve static assets through the application in dev env, but I would like to use CDN in production. Each asset is loaded into a template called base.hmtl , so I think the easiest solution is to pass the variable to the rendering function and use it in the template, for example:

 <script src="{{ STATIC_URL }}/js/main.js"></script> 

Normally this would be an empty line in dev env and url cdn during production. I would like to avoid passing this STATIC_URL variable for each view. I could make it work with

 @bp.context_processor def set_static_path(): return dict(STATIC_URL='https://foo.bar.com') 

But for me it seems a bit hacked. Is there a better way to solve this problem?

Answer 1

There is no need to change the way static files are referenced, you can still use url_for('static', filename='myfile.txt') . Replace the default static view with the one that redirects to the CDN, if configured.

 from urllib.parse import urljoin # or for python 2: from urlparse import urljoin from flask import redirect @app.endpoint('static') def static(filename): static_url = app.config.get('STATIC_URL') if static_url: return redirect(urljoin(static_url, filename)) return app.send_static_file(filename) 

Regardless of whether you work on the developer's computer or on STATIC_URL , set STATIC_URL configuration to CDN, and requests for static files will be redirected there.

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Redirects are relatively cheap and remembered by browsers. If you get to the point where they will significantly affect performance, you can write a function that communicates directly when using CDN.

 @app.template_global() def static_url(filename): static_url = app.config.get('STATIC_URL') if static_url: return urljoin(static_url, filename) return url_for('static', filename=filename) 

The template_global decorator makes the function available in all templates. Use it instead of url_for when you need links for static files.

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There may be a Flask extension that already does this for you. For example, Flask-S3 provides url_for which serves static files from AWS S3.

Answer 2

This cdn flask integration guide may be worth a read. Basically, you can install the Flask-CDN extension and define your CDN URL in the app.py file as follows:

 from flask import Flask from flask.ext.cdn import CDN app = Flask(__name__) app.config['CDN_DOMAIN'] = 'cdn.yourdomain.com' CDN(app) 

Answer 3

I had a similar problem using Flask Assets and Flask-CDN. I found that Flask-CDN is trying and cannot generate timestamps for each asset. If unsuccessful, it will return to the relative URL.

Adding app.config['CDN_TIMESTAMP'] = False problem.