Logo Questions Linux Laravel Mysql Ubuntu Git Menu
 

Using Flask, how do I modify the Cache-Control header for ALL output?

Tags:

python

http

flask

I tried using this

@app.after_request
def add_header(response):
    response.headers['Cache-Control'] = 'max-age=300'
    return response

But this causes a duplicate Cache-Control header to appear. I only want max-age=300, NOT the max-age=1209600 line!

$ curl -I http://my.url.here/
HTTP/1.1 200 OK
Date: Wed, 16 Apr 2014 14:24:22 GMT
Server: Apache
Cache-Control: max-age=300
Content-Length: 107993
Cache-Control: max-age=1209600
Expires: Wed, 30 Apr 2014 14:24:22 GMT
Content-Type: text/html; charset=utf-8
like image 444
wuxiekeji Avatar asked Apr 16 '14 14:04

wuxiekeji


People also ask

How do I change the header cache control?

To use cache-control in HTML, you use the meta tag, e.g. The value in the content field is defined as one of the four values below. HTTP 1.1. Allowed values = PUBLIC | PRIVATE | NO-CACHE | NO-STORE.

How do you set headers on a Flask response?

To set response headers in Flask and Python, we set the headers property of the response object. to call make_response to create response object that returns a string response. Finally, we return the resp object in the home route.

What should you add to a cache control response header?

private. The private response directive indicates that the response can be stored only in a private cache (e.g. local caches in browsers). You should add the private directive for user-personalized content, especially for responses received after login and for sessions managed via cookies.

What are different cache control headers?

What is the Cache-Control Header. Cache-control is an HTTP header used to specify browser caching policies in both client requests and server responses. Policies include how a resource is cached, where it's cached and its maximum age before expiring (i.e., time to live).


2 Answers

Use the response.cache_control object; this is a ResponseCacheControl() instance letting you set various cache attributes directly. Moreover, it'll make sure not to add duplicate headers if there is one there already.

@app.after_request
def add_header(response):
    response.cache_control.max_age = 300
    return response
like image 168
Martijn Pieters Avatar answered Oct 17 '22 02:10

Martijn Pieters


You can set the default value for all static files when you create the Flask application:

app = Flask(__name__)
app.config['SEND_FILE_MAX_AGE_DEFAULT'] = 300

Note that if you modify request.cache_control in after_request, as in the accepted answer, this will also modify the Cache-Control header for static files and may override the behavior you set as I showed above. I'm currently using the following code to completely disable caching for dynamically generated content but not static files:

# No cacheing at all for API endpoints.
@app.after_request
def add_header(response):
    # response.cache_control.no_store = True
    if 'Cache-Control' not in response.headers:
        response.headers['Cache-Control'] = 'no-store'
    return response

Not completely sure this is the best way, but it's working for me so far.

like image 41
aldel Avatar answered Oct 17 '22 01:10

aldel