django-dumper 0.1.1

Installation

Installation is as easy as:

pip install django-dumper

Setup

Configure the per site cache.

Then replace django.middleware.cache.FetchFromCacheMiddleware and django.middleware.cache.UpdateCacheMiddleware with dumper.middleware.FetchFromCacheMiddleware and dumper.middleware.UpdateCacheMiddleware

MIDDLEWARE_CLASSES = (
    'dumper.middleware.UpdateCacheMiddleware',
    'django.middleware.common.CommonMiddleware',
    'dumper.middleware.FetchFromCacheMiddleware',
)

Note: dumper will not work with the per view cache. If you want this support then submit an issue, it should not be too hard to implement.

Usage

To invalidate certain paths on a model save and delete, register that model using dumper.register. It will invalidate every path returned by the dependent_paths method.

from django.db import models

import dumper


class IceCream(models.Model):
    slug = models.CharField(max_length=200)

    def get_absolute_url(self):
        return '/' + self.slug

    def dependent_paths(self):
        '''Returns a list of paths to invalidate when this model is updated'''
        return [self.get_absolute_url()]

dumper.register(IceCream)

dependent_paths can also returns the paths of related objects to invalidate them as well. For instance if each IceCream had some related Sizes then if one of those sizes is modified, that should invalidate the IceCream as well.

from django.db import models

import dumper


class IceCream(models.Model):
    slug = models.CharField(max_length=200)
    sizes = models.ManyToManyField(Size, related_name='ice_creams')

    def get_absolute_url(self):
        return '/' + self.slug

    def dependent_paths(self):
        '''Returns a list of paths to invalidate when this model is updated'''
        return [self.get_absolute_url()]


class Size(models.Model):
    slug = models.CharField(max_length=200)

    def get_absolute_url(self):
        return '/' + self.slug

    def dependent_paths(self):
        for ice_cream in self.ice_creams:
            yield ice_cream.get_absolute_url()
        yield self.get_absolute_url()

dumper.register(IceCream)
dumper.register(Size)

Advice

You can set CACHE_MIDDLEWARE_SECONDS to a very long time, because each of your URLs will be invalidated when the models change. However, currently Django does not let you differentiate between backend and frontend caching. For instance, if you set it to cache for a year, then the browser would also be instructed to cache that page for a year, so even when the backend cache is invalidated the cached browser version will remain outdated. I would reccomend using django-response-timeout to set the client side cache time to a shorter length.

I also would reccomend enabling ETags. That way the whole response won’t have to be sent to the user, only the header, if the ETAG is the same.

The Django documention does not cohesively describe how your middleware should be ordered, however this stackoverflow discussion does a fine job.

Internals

So you wanna know how this all works huh? Well it might seem pretty simple. This library really has two parts. The first hooks into model saves and calls and invalidation function on all the paths returned by dependent_paths. The second actually invalidates those paths.

Contributing

If you find issues or would like to see a feature suppored, head over to the issues section and report it. Don’t be agraid, go ahead, do it!

To contribute code in any form, fork the repository and clone it locally. Create a new branch for your feature:

git commit -b feature/whatever-you-like

Then make sure all the tests past (and write new ones for any new features):

pip install -e .
pip install -r requirements-dev.txt
django-admin.py test --settings=test.settings

Check if the README.rst looks right:

restview --long-description

Then push the finished feature to github and open a pull request form the branch.