Cache Backends¶

Forwarding Backend¶

If your application needs to swap the active cache backend at runtime (for example, when offering configuration to change the cache server list or to switch between Memcached and Redis), you can make use of ForwardingCacheBackend to send cache requests to another backend.

Any operations on this backend will be forwarded to another configured backend. This backend can then be swapped out at runtime, without restarting the server.

Configuration¶

To configure this backend, place the following in settings.py:

CACHES = {
    'default': {
        'BACKEND': 'djblets.cache.forwarding_backend.ForwardingCacheBackend',
    },
    'forwarded_backend': {
        'BACKEND': 'django.core.cache.backends.memcache.PyMemcacheCache',
        'LOCATION': '127.0.0.1:11211',
    },
}

You’ll typically set this as the default cache, and will forward to forwarded_backend.

You can place ForwardingCacheBackend under any name, and change the backend it forwards to by setting its LOCATION option. For example:

CACHES = {
    'special_backend': {
        'BACKEND': 'djblets.cache.forwarding_backend.ForwardingCacheBackend',
        'LOCATION': 'other_backend',
    },
    'other_backend': {
        'BACKEND': 'django.core.cache.backends.memcache.PyMemcacheCache',
        'LOCATION': '127.0.0.1:11211',
    },
}

Forwarding to a New Backend¶

If the application updates the forwarded_backend cache backend, it must then call reset_backend() to ensure the forwarding backend will pick up the new configuration.

For example:

from django.conf import settings
from django.core.cache import cache


# Set a new forwarded cache backend.
settings.CACHES['forwarded_backend'] = {
    'BACKEND': 'django.core.cache.backends.redis.RedisCache',
    'LOCATION': 'redis://127.0.0.1:6379',
}

# Force the forwarding backend to update its settings.
cache.reset_backend()