Django Async Redis¶
Introduction¶
django-async-redis is a full featured Redis cache and session backend for Django.
- Free software: Apache Software License 2.0
- Documentation: https://django-async-redis.readthedocs.io.
Requirements¶
- Python 3.6+
- Django 3.0+
- aioredis 1.0+
- Redis server 2.8+
User guide¶
Configure as cache backend¶
To start using django-async-redis, you should change your Django cache settings to something like:
CACHES = {
"default": {
"BACKEND": "django_async_redis.cache.RedisCache",
"LOCATION": "redis://127.0.0.1:6379/1",
"OPTIONS": {
"CLIENT_CLASS": "django_async_redis.client.DefaultClient",
}
}
}
django-async-redis uses the aioredis native URL notation for connection strings, it allows better interoperability and has a connection string in more “standard” way. Some examples:
redis://[:password]@localhost:6379/0
rediss://[:password]@localhost:6379/0
unix://[:password]@/path/to/socket.sock?db=0
Three URL schemes are supported:
redis://
: creates a normal TCP socket connectionrediss://
: creates a SSL wrapped TCP socket connectionunix://
creates a Unix Domain Socket connection
There are several ways to specify a database number:
- A
db
querystring option, e.g.redis://localhost?db=0
- If using the
redis://
scheme, the path argument of the URL, e.g.redis://localhost/0
Advanced usage¶
Pickle version¶
For almost all values, django-async-redis uses pickle to serialize objects.
The latest available version of pickle is used by default. If you want set a
concrete version, you can do it, using PICKLE_VERSION
option:
CACHES = {
"default": {
# ...
"OPTIONS": {
"PICKLE_VERSION": -1 # Use the latest protocol version
}
}
}
Memcached exceptions behavior¶
In some situations, when Redis is only used for cache, you do not want exceptions when Redis is down. This is default behavior in the memcached backend and it can be emulated in django-async-redis.
For setup memcached like behaviour (ignore connection exceptions), you should
set IGNORE_EXCEPTIONS
settings on your cache configuration:
CACHES = {
"default": {
# ...
"OPTIONS": {
"IGNORE_EXCEPTIONS": True,
}
}
}
Also, you can apply the same settings to all configured caches, you can set the global flag in your settings:
DJANGO_ASYNC_REDIS_IGNORE_EXCEPTIONS = True
Log Ignored Exceptions¶
When ignoring exceptions with IGNORE_EXCEPTIONS
or
DJANGO_ASYNC_REDIS_IGNORE_EXCEPTIONS
, you may optionally log exceptions using the
global variable DJANGO_ASYNC_REDIS_LOG_IGNORED_EXCEPTIONS
in your settings file:
DJANGO_ASYNC_REDIS_LOG_IGNORED_EXCEPTIONS = True
If you wish to specify the logger in which the exceptions are output, simply
set the global variable DJANGO_ASYNC_REDIS_LOGGER
to the string name and/or path
of the desired logger. This will default to __name__
if no logger is
specified and DJANGO_ASYNC_REDIS_LOG_IGNORED_EXCEPTIONS
is True
:
DJANGO_ASYNC_REDIS_LOGGER = 'some.specified.logger'
Infinite timeout¶
django-async-redis comes with infinite timeouts support out of the box. And it behaves in the same way as the Django BaseCache backend specifies:
timeout=0
expires the value immediately.timeout=None
infinite timeout
await cache.set_async("key", "value", timeout=None)
Get ttl (time-to-live) from key¶
With Redis, you can access to ttl of any stored key, for it,
django-async-redis exposes ttl_async
function.
It returns:
- 0 if key does not exists (or already expired).
- None for keys that exists but does not have any expiration.
- ttl value for any volatile key (any key that has expiration).
>>> from django.core.cache import cache
>>> await cache.set_async("foo", "value", timeout=25)
>>> await cache.ttl_async("foo")
25
>>> await cache.ttl_async("not-existent")
0
Expire & Persist¶
Additionally to the simple ttl query, you can send persist a concrete key or
specify a new expiration timeout using the persist_async
and expire_async
methods:
>>> await cache.set_async("foo", "bar", timeout=22)
>>> await cache.ttl_async("foo")
22
>>> await cache.persist_async("foo")
>>> await cache.ttl_async("foo")
None
>>> await cache.set_async("foo", "bar", timeout=22)
>>> await cache.expire_async("foo", timeout=5)
>>> await cache.ttl_async("foo")
5
Scan & Delete keys in bulk¶
django-async-redis comes with some additional methods that help with searching or deleting keys using glob patterns.
>>> from django.core.cache import cache
>>> await cache.keys_async("foo_*")
["foo_1", "foo_2"]
A simple search like this will return all matched values. In databases with a
large number of keys this isn’t suitable method. Instead, you can use the
iter_keys_async
function that works like the keys_async
function but uses Redis
server side cursors. Calling iter_keys_async
will return a generator that you can
then iterate over efficiently.
>>> from django.core.cache import cache
>>> await cache.iter_keys_async("foo_*")
<async_generator object algo at 0x7ffa9c2713a8>
>>> (await cache.iter_keys_async("foo_*")).__anext__()
"foo_1"
For deleting keys, you should use delete_pattern_async
which has the same glob
pattern syntax as the keys_async
function and returns the number of deleted keys.
>>> from django.core.cache import cache
>>> await cache.delete_pattern_async("foo_*")
Redis native commands¶
django-async-redis has limited support for some Redis atomic operations, such as the
commands SETNX
and INCR
.
You can use the SETNX
command through the backend set_async()
method with
the nx
parameter:
>>> from django.core.cache import cache
>>> await cache.set_async("key", "value1", nx=True)
True
>>> await cache.set_async("key", "value2", nx=True)
False
>>> await cache.get_async("key")
"value1"
Also, the incr_async
and decr_async
methods use Redis atomic
operations when the value that a key contains is suitable for it.
Note that setting xx
to True overrides the nx
flag according
to aioredis.
Connection pools¶
Behind the scenes, django-async-redis uses the underlying aioredis connection pool implementation and exposes a simple way to configure it. Alternatively, you can directly customize a connection/connection pool creation for a backend.
The default aioredis behavior is to not close connections, recycling them when possible.
Notes¶
Since the majority of this code was ported from django-redis, there was one
case that had needed a monkeypatch. In django_async_redis.util
, we implement
CacheKey
which subclasses str
which helps us know if a cache key was
already created. Since aioredis, checks if the cache key is of type str
(and others), I had to monkeypatch that check so that a CacheKey instance could
also be accepted.
Credit¶
- Hey, I’m Andrew. I’m busy in college, but I wanted to help contribute to Django’s async ecosystem.
- Lots of code and docs is taken from django-redis, including the tests. I just needed to port everything to asyncio and aioredis.
- I used cookiecutter-pypackage to generate this project.
- Thank you to Python Discord server’s async topical chat for helping me understand when to use coroutines over sync functions and @Bast and @hmmmm in general because they’re OG.