The #cache_page decorator is awesome. But for my blog I would like to keep a page in cache until someone comments on a post. This sounds like a great idea as people rarely comment so keeping the pages in memcached while nobody comments would be great. I'm thinking that someone must have had this problem before? And this is different than caching per url.
So a solution I'm thinking of is:
#cache_page( 60 * 15, "blog" );
def blog( request ) ...
And then I'd keep a list of all cache keys used for the blog view and then have way of expire the "blog" cache space. But I'm not super experienced with Django so I'm wondering if someone knows a better way of doing this?
This solution works for django versions before 1.7
Here's a solution I wrote to do just what you're talking about on some of my own projects:
def expire_view_cache(view_name, args=[], namespace=None, key_prefix=None):
"""
This function allows you to invalidate any view-level cache.
view_name: view function you wish to invalidate or it's named url pattern
args: any arguments passed to the view function
namepace: optioal, if an application namespace is needed
key prefix: for the #cache_page decorator for the function (if any)
"""
from django.core.urlresolvers import reverse
from django.http import HttpRequest
from django.utils.cache import get_cache_key
from django.core.cache import cache
# create a fake request object
request = HttpRequest()
# Loookup the request path:
if namespace:
view_name = namespace + ":" + view_name
request.path = reverse(view_name, args=args)
# get cache key, expire if the cached item exists:
key = get_cache_key(request, key_prefix=key_prefix)
if key:
if cache.get(key):
# Delete the cache entry.
#
# Note that there is a possible race condition here, as another
# process / thread may have refreshed the cache between
# the call to cache.get() above, and the cache.set(key, None)
# below. This may lead to unexpected performance problems under
# severe load.
cache.set(key, None, 0)
return True
return False
Django keys these caches of the view request, so what this does is creates a fake request object for the cached view, uses that to fetch the cache key, then expires it.
To use it in the way you're talking about, try something like:
from django.db.models.signals import post_save
from blog.models import Entry
def invalidate_blog_index(sender, **kwargs):
expire_view_cache("blog")
post_save.connect(invalidate_portfolio_index, sender=Entry)
So basically, when ever a blog Entry object is saved, invalidate_blog_index is called and the cached view is expired. NB: haven't tested this extensively, but it's worked fine for me so far.
The cache_page decorator will use CacheMiddleware in the end which will generate a cache key based on the request (look at django.utils.cache.get_cache_key) and the key_prefix ("blog" in your case). Note that "blog" is only a prefix, not the whole cache key.
You can get notified via django's post_save signal when a comment is saved, then you can try to build the cache key for the appropriate page(s) and finally say cache.delete(key).
However this requires the cache_key, which is constructed with the request for the previously cached view. This request object is not available when a comment is saved. You could construct the cache key without the proper request object, but this construction happens in a function marked as private (_generate_cache_header_key), so you are not supposed to use this function directly. However, you could build an object that has a path attribute that is the same as for the original cached view and Django wouldn't notice, but I don't recommend that.
The cache_page decorator abstracts caching quite a bit for you and makes it hard to delete a certain cache object directly. You could make up your own keys and handle them in the same way, but this requires some more programming and is not as abstract as the cache_page decorator.
You will also have to delete multiple cache objects when your comments are displayed in multiple views (i.e. index page with comment counts and individual blog entry pages).
To sum up: Django does time based expiration of cache keys for you, but custom deletion of cache keys at the right time is more tricky.
I wrote Django-groupcache for this kind of situations (you can download the code here). In your case, you could write:
from groupcache.decorators import cache_tagged_page
#cache_tagged_page("blog", 60 * 15)
def blog(request):
...
From there, you could simply do later on:
from groupcache.utils import uncache_from_tag
# Uncache all view responses tagged as "blog"
uncache_from_tag("blog")
Have a look at cache_page_against_model() as well: it's slightly more involved, but it will allow you to uncache responses automatically based on model entity changes.
With the latest version of Django(>=2.0) what you are looking for is very easy to implement:
from django.utils.cache import learn_cache_key
from django.core.cache import cache
from django.views.decorators.cache import cache_page
keys = set()
#cache_page( 60 * 15, "blog" );
def blog( request ):
response = render(request, 'template')
keys.add(learn_cache_key(request, response)
return response
def invalidate_cache()
cache.delete_many(keys)
You can register the invalidate_cache as a callback when someone updates a post in the blog via a pre_save signal.
This won't work on django 1.7; as you can see here https://docs.djangoproject.com/en/dev/releases/1.7/#cache-keys-are-now-generated-from-the-request-s-absolute-url the new cache keys are generated with the full URL, so a path-only fake request won't work. You must setup properly request host value.
fake_meta = {'HTTP_HOST':'myhost',}
request.META = fake_meta
If you have multiple domains working with the same views, you should cycle them in the HTTP_HOST, get proper key and do the clean for each one.
Django view cache invalidation for v1.7 and above. Tested on Django 1.9.
def invalidate_cache(path=''):
''' this function uses Django's caching function get_cache_key(). Since 1.7,
Django has used more variables from the request object (scheme, host,
path, and query string) in order to create the MD5 hashed part of the
cache_key. Additionally, Django will use your server's timezone and
language as properties as well. If internationalization is important to
your application, you will most likely need to adapt this function to
handle that appropriately.
'''
from django.core.cache import cache
from django.http import HttpRequest
from django.utils.cache import get_cache_key
# Bootstrap request:
# request.path should point to the view endpoint you want to invalidate
# request.META must include the correct SERVER_NAME and SERVER_PORT as django uses these in order
# to build a MD5 hashed value for the cache_key. Similarly, we need to artificially set the
# language code on the request to 'en-us' to match the initial creation of the cache_key.
# YMMV regarding the language code.
request = HttpRequest()
request.META = {'SERVER_NAME':'localhost','SERVER_PORT':8000}
request.LANGUAGE_CODE = 'en-us'
request.path = path
try:
cache_key = get_cache_key(request)
if cache_key :
if cache.has_key(cache_key):
cache.delete(cache_key)
return (True, 'successfully invalidated')
else:
return (False, 'cache_key does not exist in cache')
else:
raise ValueError('failed to create cache_key')
except (ValueError, Exception) as e:
return (False, e)
Usage:
status, message = invalidate_cache(path='/api/v1/blog/')
I had same problem and I didn't want to mess with HTTP_HOST, so I created my own cache_page decorator:
from django.core.cache import cache
def simple_cache_page(cache_timeout):
"""
Decorator for views that tries getting the page from the cache and
populates the cache if the page isn't in the cache yet.
The cache is keyed by view name and arguments.
"""
def _dec(func):
def _new_func(*args, **kwargs):
key = func.__name__
if kwargs:
key += ':' + ':'.join([kwargs[key] for key in kwargs])
response = cache.get(key)
if not response:
response = func(*args, **kwargs)
cache.set(key, response, cache_timeout)
return response
return _new_func
return _dec
To expired page cache just need to call:
cache.set('map_view:' + self.slug, None, 0)
where self.slug - param from urls.py
url(r'^map/(?P<slug>.+)$', simple_cache_page(60 * 60 * 24)(map_view), name='map'),
Django 1.11, Python 3.4.3
FWIW I had to modify mazelife's solution to get it working:
def expire_view_cache(view_name, args=[], namespace=None, key_prefix=None, method="GET"):
"""
This function allows you to invalidate any view-level cache.
view_name: view function you wish to invalidate or it's named url pattern
args: any arguments passed to the view function
namepace: optioal, if an application namespace is needed
key prefix: for the #cache_page decorator for the function (if any)
from: http://stackoverflow.com/questions/2268417/expire-a-view-cache-in-django
added: method to request to get the key generating properly
"""
from django.core.urlresolvers import reverse
from django.http import HttpRequest
from django.utils.cache import get_cache_key
from django.core.cache import cache
# create a fake request object
request = HttpRequest()
request.method = method
# Loookup the request path:
if namespace:
view_name = namespace + ":" + view_name
request.path = reverse(view_name, args=args)
# get cache key, expire if the cached item exists:
key = get_cache_key(request, key_prefix=key_prefix)
if key:
if cache.get(key):
cache.set(key, None, 0)
return True
return False
Instead of using the cache page decorator, you could manually cache the blog post object (or similar) if there are no comments, and then when there's a first comment, re-cache the blog post object so that it's up to date (assuming the object has attributes that reference any comments), but then just let that cached data for the commented blog post expire and then no bother re-cacheing...
Instead of explicit cache expiration you could probably use new "key_prefix" every time somebody comment the post. E.g. it might be datetime of the last post's comment (you could even combine this value with the Last-Modified header).
Unfortunately Django (including cache_page()) does not support dynamic "key_prefix"es (checked on Django 1.9) but there is workaround exists. You can implement your own cache_page() which may use extended CacheMiddleware with dynamic "key_prefix" support included. For example:
from django.middleware.cache import CacheMiddleware
from django.utils.decorators import decorator_from_middleware_with_args
def extended_cache_page(cache_timeout, key_prefix=None, cache=None):
return decorator_from_middleware_with_args(ExtendedCacheMiddleware)(
cache_timeout=cache_timeout,
cache_alias=cache,
key_prefix=key_prefix,
)
class ExtendedCacheMiddleware(CacheMiddleware):
def __init__(self, *args, **kwargs):
super().__init__(*args, **kwargs)
if callable(self.key_prefix):
self.key_function = self.key_prefix
def key_function(self, request, *args, **kwargs):
return self.key_prefix
def get_key_prefix(self, request):
return self.key_function(
request,
*request.resolver_match.args,
**request.resolver_match.kwargs
)
def process_request(self, request):
self.key_prefix = self.get_key_prefix(request)
return super().process_request(request)
def process_response(self, request, response):
self.key_prefix = self.get_key_prefix(request)
return super().process_response(request, response)
Then in your code:
from django.utils.lru_cache import lru_cache
#lru_cache()
def last_modified(request, blog_id):
"""return fresh key_prefix"""
#extended_cache_page(60 * 15, key_prefix=last_modified)
def view_blog(request, blog_id):
"""view blog page with comments"""
Most of the solutions above didn't work in our case because we use https. The source code for get_cache_key reveals that it uses request.get_absolute_uri() to generate the cache key.
The default HttpRequest class sets the scheme as http. Thus we need to override it to use https for our dummy request object.
This is the code that works fine for us :)
from django.core.cache import cache
from django.http import HttpRequest
from django.utils.cache import get_cache_key
class HttpsRequest(HttpRequest):
#property
def scheme(self):
return "https"
def invalidate_cache_page(
path,
query_params=None,
method="GET",
):
request = HttpsRequest()
# meta information can be checked from error logs
request.META = {
"SERVER_NAME": "www.yourwebsite.com",
"SERVER_PORT": "443",
"QUERY_STRING": query_params,
}
request.path = path
key = get_cache_key(request, method=method)
if cache.has_key(key):
cache.delete(key)
Now I can use this utility function to invalidate the cache from any of our views:
page = reverse('url_name', kwargs={'id': obj.id})
invalidate_cache_page(path)
Duncan's answer works well with Django 1.9. But if we need invalidate url with GET-parameter we have to make a little changes in request.
Eg for .../?mykey=myvalue
request.META = {'SERVER_NAME':'127.0.0.1','SERVER_PORT':8000, 'REQUEST_METHOD':'GET', 'QUERY_STRING': 'mykey=myvalue'}
request.GET.__setitem__(key='mykey', value='myvalue')
I struggled with a similar situation and here is the solution I came up with, I started it on an earlier version of Django but it is currently in use on version 2.0.3.
First issue: when you set things to be cached in Django, it sets headers so that downstream caches -- including the browser cache -- cache your page.
To override that, you need to set middleware. I cribbed this from elsewhere on StackOverflow, but can't find it at the moment. In appname/middleware.py:
from django.utils.cache import add_never_cache_headers
class Disable(object):
def __init__(self, get_response):
self.get_response = get_response
def __call__(self, request):
response = self.get_response(request)
add_never_cache_headers(response)
return response
Then in settings.py, to MIDDLEWARE, add:
'appname.middleware.downstream_caching.Disable',
Keep in mind that this approach completely disables downstream caching, which may not be what you want.
Finally, I added to my views.py:
def expire_page(request, path=None, query_string=None, method='GET'):
"""
:param request: "real" request, or at least one providing the same scheme, host, and port as what you want to expire
:param path: The path you want to expire, if not the path on the request
:param query_string: The query string you want to expire, as opposed to the path on the request
:param method: the HTTP method for the page, if not GET
:return: None
"""
if query_string is not None:
request.META['QUERY_STRING'] = query_string
if path is not None:
request.path = path
request.method = method
# get_raw_uri and method show, as of this writing, everything used in the cache key
# print('req uri: {} method: {}'.format(request.get_raw_uri(), request.method))
key = get_cache_key(request)
if key in cache:
cache.delete(key)
I didn't like having to pass in a request object, but as of this writing, it provides the scheme/protocol, host, and port for the request, pretty much any request object for your site/app will do, as long as you pass in the path and query string.
One more updated version of Duncan's answer: had to figure out correct meta fields: (tested on Django 1.9.8)
def invalidate_cache(path=''):
import socket
from django.core.cache import cache
from django.http import HttpRequest
from django.utils.cache import get_cache_key
request = HttpRequest()
domain = 'www.yourdomain.com'
request.META = {'SERVER_NAME': socket.gethostname(), 'SERVER_PORT':8000, "HTTP_HOST": domain, 'HTTP_ACCEPT_ENCODING': 'gzip, deflate, br'}
request.LANGUAGE_CODE = 'en-us'
request.path = path
try:
cache_key = get_cache_key(request)
if cache_key :
if cache.has_key(cache_key):
cache.delete(cache_key)
return (True, 'successfully invalidated')
else:
return (False, 'cache_key does not exist in cache')
else:
raise ValueError('failed to create cache_key')
except (ValueError, Exception) as e:
return (False, e)
The solution is simple, and do not require any additional work.
Example
#cache_page(60 * 10)
def our_team(request, sorting=None):
...
This will set the response to the cache with the default key.
Expire a view cache
from django.utils.cache import get_cache_key
from django.core.cache import cache
def our_team(request, sorting=None):
# This will remove the cache value and set it to None
cache.set(get_cache_key(request), None)
Simple, Clean, Fast.
I am trying to set my Django app work with multiple domains (while serving slightly different content)
I wrote this middleware:
class MultiSiteMiddleware(object):
def process_request(self, request):
host = request.get_host()
host_part = host.split(':')[0].split('.com')[0].split('.')
host = host_part[len(host_part)-1] + '.com'
site = Site.objects.get(domain=host)
settings.SITE_ID = site.id
settings.CURRENT_HOST = host
Site.objects.clear_cache()
return
In views I use this:
def get_site(request):
current_site = get_current_site(request)
return current_site.name
def view(request, pk):
site = get_site(request)
if site == 'site1':
# serve content1
...
elif site == 'site2'
# serve content2
...
But now there are 404 errors (I sometimes find them in logs, don't see them while browsing my site manually) where they aren't supposed to be, like my site sometimes is serving content for wrong domains, can they happen because of some flaw in the above middleware and view code or I should look somewhere else?
I had a similar requirement and decided not to use the django sites framework. My middleware looks like
class MultiSiteMiddleware(object):
def process_request(self, request):
try:
domain = request.get_host().split(":")[0]
request.site = Site.objects.get(domain=domain)
except Site.DoesNotExist:
return http.HttpResponseNotFound()
then my views have access to request.site
If you're seeing 404's for sites that aren't yours in your logs it would seem like somebody has pointed their domain at your servers IP address, you could use apache/nginx to filter these out before they hit your app, but your middleware should catch them (though possibly by raising an uncaught 500 error instead of a 404)
Serve multiple domain from one website (django1.8 python3+)
The goal is, obviously, to serve multiple domains, from one Django instance. That means, we use the same models, the same database, the same logic, the same views, the same templates, but to serve different things.
Searching the interwebs, I came to the idea of using the sites framework. The sites framework was designed to do exactly that thing. In fact, the sites framework has been used to do exactly that. But I haven't been able to know on which version of Django it was, and actually, I came to the idea the sites framework was just a vestigial module. Basically, it is just a table, with SITE_ID and SITE_URL, that you can easily access with a function. But I've been unable to find how, from that, you can do a multi-domain website.
So my idea has been, how to modify the url resolver. The idea behind all these is easy : www.domain1.com/bar is resolved to /domain1/bar, and www.domain2.foo is resolved to /domain2/foo. This solves the problem because, if you want to serve multiple domains, you just have to serve multiple folders.
In Django, to achieve this, you have to modify two things :
* the way Django routes requests
* the way django write urls
The way Django routes requests
Django routes requests with middlewares. That's it. So we just have to write a middleware that re-route requests.
To make it easier, middlewares can have a process_request method that process requests (WOW), before requests are handled. So let's write a DomainNameMiddleware
#!python
#app/middleware.py
class DomaineNameMiddleware:
"""
change the request path to add the domain_name at the first
"""
def process_request(self, request):
#first, we split the domain name, and take the part before the extension
request_domain = request.META['HTTP_HOST'].split('.')[-2]
request.path_info = "/%s/%s" % (request_domain, request.path.split('/')[1:])
The way Django writes URL
When I'm talking about django writing url, i'm principally thinking of the {% url %} template tag, the get_absolute_url methods, the resolve and resolve_lazy functions, and those basic Django thing. If we rewrite the way Django handle url, we have to tell Django to write url that way.
But basically it's pretty easy, thanks to Django.
You can easily rewrite basic Django function by just rewriting them, typically in init.py files of modules you added as apps. So :
#!python
#anyapp/__init__.py
from django.core import urlresolvers
old_reverse = urlresolvers.reverse
def new_reverse(viewname, urlconf=None, args=None, kwargs=None, current_app=None):
"""
return an url with the first folder as a domain name in .com
"""
TLD = 'com'
old_reverse_url = old_reverse(viewname, urlconf, args, kwargs, current_app)
# admin will add itself everytime you reload an admin page, so we have to delete it
if current_app == 'admin':
return '/%s' % old_reverse_url[len('admin'):].replace('adminadmin', 'admin')
return '//%s.%s/%s' % (app, TLD, path)
How to use it ?
I use it with base urls.py as dispatchedr.
#!python
#urls.py
from django.conf.urls import include, url
from domain1 import urls as domain1_urls
from domain2 import urls as domain2_urls
urlpatterns = [
url(r'^domain1/', include(domain1_urls, namespace='domain1')),
url(r'^domain2/', include(domain2_urls, namespace='domain2)),
]
Django's Sites framework has built-in middleware to accomplish this.
Simply enable the Sites framework and add this to your MIDDLEWARE:
'django.contrib.sites.middleware.CurrentSiteMiddleware'
This automatically passes a request object to Site.objects.get_current() on every request. It solves your problem by giving you access to request.site on every request.
For reference, the code as of 1.11 is:
from django.utils.deprecation import MiddlewareMixin
from .shortcuts import get_current_site
class CurrentSiteMiddleware(MiddlewareMixin):
"""
Middleware that sets `site` attribute to request object.
"""
def process_request(self, request):
request.site = get_current_site(request)
I will suggest you to use django-multisite .It will fulfill your requirement.
Try using the "sites" framework in django to get the domain name. You already know this I guess.
Take a look here: https://docs.djangoproject.com/en/1.7/ref/contrib/sites/#getting-the-current-domain-for-full-urls
See this:
>>> Site.objects.get_current().domain
'example.com'
Without the https://www or http://www.. Probably your domains will end in .org or some country .pe .ru etc not just .com.
There might be a case when people don't point to your domain but to your IP address for some reason, maybe development of testing so you should always raise an exception with Site.DoesNotExist
I'm running memcached infront of django without any explicit configuration in my code. I.e. nothing more than
MIDDLEWARE_CLASSES = (
'django.middleware.cache.UpdateCacheMiddleware',
...
'django.middleware.cache.FetchFromCacheMiddleware',
)
and
CACHE_BACKEND = 'memcached://127.0.0.1:11211/'
in my settings.py. This works great, in fact so great that it's caching my admin page leaving me no way to moderate live actions on the site until the cache refetches the data. Is there a regex I can throw somewhere to let memcached know to leave my admin page alone? (I'm also using nginx and gunicorn)
You can maybe write your own middleware class or extend from one that django provides.
Specify a dictionary of urls in your settings file:
CACHE_IGNORE_REGEXPS = (
)
Write a Middleware Class:
from django.core.cache import cache
import re
import settings
class MyMemCacheMiddleWare:
def process_response(self, request, response):
cacheIt = True
theUrl = request.get_full_path()
# if it's a GET then store it in the cache:
if request.method != 'GET':
cacheIt = False
# loop on our CACHE_INGORE_REGEXPS and ignore
# certain urls.
for exp in settings.CACHE_IGNORE_REGEXPS:
if re.match(exp,theUrl):
cacheIt = False
if cacheIt:
key = '%s-%s' % (settings.CACHE_KEY_PREFIX,theUrl)
cache.set(key,response.content)
return response
Alex Holt has a pretty neat tutorial about django, memcached and Nginx maybe you wanna read through that to get a better idea.
I had the same exact problem and I came up with an another minimal solution.
First, create your own middleware that inherits the original UpdateCacheMiddleware:
#! /usr/bin/env python
from django.conf import settings
from django.middleware.cache import UpdateCacheMiddleware
class MyUpdateCacheMiddleware(UpdateCacheMiddleware):
def process_response(self, request, response):
full_path = request.get_full_path()
# loop on our CACHE_MIDDLEWARE_IGNORE to ignore certain urls
for ignore in settings.CACHE_MIDDLEWARE_IGNORE:
if ignore.match(full_path):
return response
# ignore patterns missed, pass it to the original middleware
return super(MyUpdateCacheMiddleware, self).process_response(
request, response
)
Then create an ignore regex list in your settings similar to that:
CACHE_MIDDLEWARE_IGNORE = (
re.compile(r'^/admin/'),
)
Now all you need to do is to replace your UpdateCacheMiddleware with the one you created:
MIDDLEWARE_CLASSES = (
'myapp.lib.middlewares.MyUpdateCacheMiddleware',
# ...
'django.middleware.cache.FetchFromCacheMiddleware',
)
Cheers.
I've been using the following SSLMiddleware on Linode for a while, and my SSL worked perfectly on that, now I've changed my server to Webfaction, and all of sudden, my HTTPS pages are not working in a way as it's redirected to https page correctly, but all my css files, images within the css files(no absolute url), javascript have all become non secure sources(referring to http:// instead of https://), I'm really puzzled right now as I don't know if it's got to do with SSLMiddleware or something else, I haven't changed anything in settings.py either apart from database parameter value.. Please help. Thanks in advance.
__license__ = "Python"
__copyright__ = "Copyright (C) 2007, Stephen Zabel"
__author__ = "Stephen Zabel - sjzabel#gmail.com"
__contributors__ = "Jay Parlar - parlar#gmail.com"
from django.conf import settings
from django.http import HttpResponseRedirect, HttpResponsePermanentRedirect, get_host
SSL = 'SSL'
class SSLRedirect:
def process_view(self, request, view_func, view_args, view_kwargs):
if SSL in view_kwargs:
secure = view_kwargs[SSL]
del view_kwargs[SSL]
else:
secure = False
if settings.ENABLE_SSL:
if not secure == self._is_secure(request):
return self._redirect(request, secure)
else:
return
def _is_secure(self, request):
if request.is_secure():
return True
#Handle the Webfaction case until this gets resolved in the request.is_secure()
if 'HTTP_X_FORWARDED_SSL' in request.META:
return request.META['HTTP_X_FORWARDED_SSL'] == 'on'
return False
def _redirect(self, request, secure):
protocol = secure and "https" or "http"
newurl = "%s://%s%s" % (protocol,get_host(request),request.get_full_path())
if settings.DEBUG and request.method == 'POST':
raise RuntimeError, \
"""Django can't perform a SSL redirect while maintaining POST data.
Please structure your views so that redirects only occur during GETs."""
return HttpResponsePermanentRedirect(newurl)
I recently implemented SSL on WebFaction without any custom Middleware tinkering and it was a very straightforward process.
Have a look here: http://community.webfaction.com/questions/512/how-do-i-set-up-a-https-ssl-django-site
If that doesn't help, open up a ticket with them. They're usually very good about resolving issues very quickly.