Opened 16 years ago

Closed 16 years ago

Last modified 16 years ago

#7398 closed (fixed)

Making it easier to add custom cache backends

Reported by: lau@… Owned by: nobody
Component: Core (Cache system) Version: dev
Severity: Keywords:
Cc: lau@… Triage Stage: Accepted
Has patch: yes Needs documentation: no
Needs tests: no Patch needs improvement: no
Easy pickings: no UI/UX: no

Description

I ran into an inconvenience with the Django cache. I wanted to add my own custom cache backend without having to muck about with the Django core. This proved to be a bit challenging since the backend importer uses a complete path to the module (e.g. "django.core.cache.backends.memcached").

I did a small patch which lets you define extra backend modules without touching the Django folder. Essentially it uses the BACKENDS dictionary in core/cache/init.py to keep information about the full import paths, like this:

BACKENDS = {
    # name for use in settings file --> path to the backend module
    'memcached': 'django.core.cache.backends.memcached',
    'locmem': 'django.core.cache.backends.locmem',
    'file': 'django.core.cache.backends.filebased',
    'db': 'django.core.cache.backends.db',
    'dummy': 'django.core.cache.backends.dummy',
}

if hasattr(settings, "CACHE_BACKEND_MODULES"):
    BACKENDS.update(settings.CACHE_BACKEND_MODULES)

So if I wanted to add a new backend in my project, I'd do something like:

settings.py:

CACHE_BACKEND_MODULES = {
    'penandpaper': 'backends.cache.penandpaper'
}

and place the backend in my_app/backends/cache/.

There has been a bit of talk about it lately on the developer mailing list:

http://groups.google.com/group/django-developers/browse_thread/thread/e0fbaff909c44336

Attachments (3)

ease-custom-cache-backends.diff (1.4 KB ) - added by lau@… 16 years ago.
Ease custom cache backends
ease-custom-cache-backends-with-documentation.diff (2.2 KB ) - added by lau@… 16 years ago.
Added documentation in docs/settings.txt
importable-backends.diff (4.2 KB ) - added by theillustratedlife 16 years ago.
Allows CACHE_BACKEND to be a path - doc formatting corrected

Download all attachments as: .zip

Change History (19)

by lau@…, 16 years ago

Ease custom cache backends

comment:1 by Jacob, 16 years ago

Needs documentation: set

by lau@…, 16 years ago

Added documentation in docs/settings.txt

comment:2 by Matt McClanahan, 16 years ago

Needs documentation: unset

comment:3 by lau@…, 16 years ago

Let me know if there's anything else in the way of this ticket.

comment:4 by lau@…, 16 years ago

Any news on getting this in?

comment:5 by theillustratedlife, 16 years ago

Triage Stage: UnreviewedReady for checkin

comment:6 by Malcolm Tredinnick, 16 years ago

Patch needs improvement: set
Triage Stage: Ready for checkinAccepted

I think a whole extra setting and a dictionary like this is too much for this feature. Let's handle it like database backends: if the cache name (the bit before the colon, ":") is not one of the standard names, it's treated as an import path. Everything after the colon is passed through as an argument, just like now.

So extra caches can be added anywhere on the Python path and we don't need an extra setting. Being able to redefine the existing names to mean something else isn't needed here. If you want to have "some other memcached", just import it under a different name using the extension mechanism in the above paragraph. The point is that every time we add an extra setting, it's one more bit of documentation, one more thing for people to wonder if they need, etc. Let's go for simplicity first.

comment:7 by theillustratedlife, 16 years ago

So, you're proposing something like this in settings.py:

CACHE_BACKEND = "backends.cache.penandpaper://"

with something like this in django.core.conf:

backend_import = scheme
if hasattr(BACKENDS, scheme):
    backend_import = BACKENDS[scheme]

    cache_class = getattr(__import__(backend_import, {}, {}, ['']), 'CacheClass')

Correct?

in reply to:  7 comment:8 by theillustratedlife, 16 years ago

*django.core.cache

Sorry for the typo (and the additional post).

comment:9 by Malcolm Tredinnick, 16 years ago

Yes, that's the idea.

by theillustratedlife, 16 years ago

Attachment: importable-backends.diff added

Allows CACHE_BACKEND to be a path - doc formatting corrected

in reply to:  9 comment:10 by theillustratedlife, 16 years ago

Patch needs improvement: unset

I put together a patch to implement what we discussed earlier. Please take a peek and let me know what you think. =)

comment:11 by Lau Bech Lauritzen <lau@…>, 16 years ago

Okay then, sounds good. Looking forward to seeing it in svn.

comment:12 by Michael Radziej, 16 years ago

milestone: post-1.0

comment:13 by Malcolm Tredinnick, 16 years ago

Resolution: fixed
Status: newclosed

(In [8075]) Fixed #7398 -- Allow for custom cache-backends to be used.

Based on a patch from Lau Bech Lauritzen and Brenton Simpson.

comment:14 by theillustratedlife, 16 years ago

Thanks!

comment:15 by Lau Bech Lauritzen <lau@…>, 16 years ago

And thanks from here as well!

comment:16 by (none), 16 years ago

milestone: post-1.0

Milestone post-1.0 deleted

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