slick ORM cache and invalidation for Django
Project description
A slick app that supports automatic or manual queryset caching and automatic granular event-driven invalidation. It can also cache results of user functions and invalidate them by time or the same way as querysets.
It uses redis as backend for ORM cache and redis or filesystem for simple time-invalidated one.
Requirements
Installation
Using pip:
$ pip install django-cacheops
Or you can get latest one from github:
$ git clone git://github.com/Suor/django-cacheops.git $ ln -s `pwd`/django-cacheops/cacheops/ /somewhere/on/your/python/import/path/
Setup
Add cacheops to your INSTALLED_APPS first:
INSTALLED_APPS = (
'cacheops',
...
)
Setup redis connection and enable caching for desired models:
CACHEOPS_REDIS = {
'host': 'localhost', # redis-server is on same machine
'port': 6379, # default redis port
#'db': 1, # SELECT non-default redis database
'socket_timeout': 3,
}
CACHEOPS = {
# Automatically cache any User.objects.get() calls for 15 minutes
# This includes request.user or post.author access,
# where Post.author is a foreign key to auth.User
'auth.user': ('get', 60*15),
# Automatically cache all gets, queryset fetches and counts
# to other django.contrib.auth models for an hour
'auth.*': ('all', 60*60),
# Enable manual caching on all news models with default timeout of an hour
# Use News.objects.cache().get(...)
# or Tags.objects.filter(...).order_by(...).cache()
# to cache particular ORM request.
# Invalidation is still automatic
'news.*': ('just_enable', 60*60),
# Automatically cache count requests for all other models for 15 min
'*.*': ('count', 60*15),
}
Usage
It’s automatic you just need to set it up.
You can force any queryset to use cache by calling it’s .cache() method:
Article.objects.filter(tag=2).cache()
Here you can specify which ops should be cached for queryset, for example, this code:
qs = Article.objects.filter(tag=2).cache(ops=['count']) paginator = Paginator(objects, ipp) articles = list(pager.page(page_num)) # hits database
will cache .count() call in Paginator but not later in articles fetch. There are three possible actions - get, fetch and count. You can pass any subset of this ops to .cache() method even empty to turn off caching. There are, however, a shortcut for it:
qs = Article.objects.filter(visible=True).nocache() qs1 = qs.filter(tag=2) # hits database qs2 = qs.filter(category=3) # hits it once more
It is usefull when you want to disable automatic caching on particular queryset.
You can cache and invalidate result of a function the same way as a queryset. Cache of next function will be invalidated on any Article change, addition or deletetion:
from cacheops import cacheoped_as
@cacheoped_as(Article.objects.all())
def article_stats():
return {
'tags': list( Article.objects.values('tag').annotate(count=Count('id')) )
'categories': list( Article.objects.values('category').annotate(count=Count('id')) )
}
Note that we are using list on both querysets here, it’s because we don’t want to cache queryset objects but their result.
Also note that cache key does not depend on arguments of a function, so it’s result should not, either. This is done to enable caching of view functions. Instead you should use a local function:
def articles_block(category, count=5):
@cacheoped_as(Article.objects.filter(category=category), extra=count)
def _articles_block():
qs = Article.objects.filter(category=category)
articles = list(qs.filter(photo=True)[:count])
if len(articles) < count:
articles += list(qs[:count-len(articles)])
return articles
return _articles_block()
Using local function gives additional advantage: we can filter queryset used in @cacheoped_as() to make invalidation more granular. We also add an extra to make diffrent keys for calls with same category but diffrent count.
Invalidation
Cacheops uses both time and event-driven invalidation and is fully automatic. The event-driven one listens on model signals and invalidates appropriate caches on Model.save() and .delete().
Usually you won’t need to do anything with it.
TODO
write how smart is it,
docs about invalidate command
docs about simple cache
docs about file_cache
add .delete(cache_key) method to simple and file cache
.invalidate() method on simple cached funcs
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