Django Redis cache get TTL (expire time)

Question

Is it possible to get key's expire time in Django using Redis cache?
Something like:

from django.core.cache import cache  

cache.get_expire('mykey')  # 300 (seconds)

I tried:

cache.ttl('my_key')  

getting an error

AttributeError: 'RedisCache' object has no attribute 'ttl'

Answer 1

There is no official API to get TTL from RedisCache backend in Django (as of Django 4.2); but we can customize the backend like -

# somefile.py

from functools import cached_property

from django.core.cache.backends.redis import (
    RedisCache as _RedisCache,
    RedisCacheClient as _RedisCacheClient,
)


class RedisCacheClient(_RedisCacheClient):
    def ttl(self, key):
        client = self.get_client(key)
        return client.ttl(key)


class RedisCache(_RedisCache):
    @cached_property
    def _cache(self):
        return RedisCacheClient(self._servers, **self._options)

    def ttl(self, key, version=None):
        key = self.make_and_validate_key(key, version=version)
        return self._cache.ttl(key)

and then update your settings.py

# settings.py

CACHES = {
    "default": {
        "BACKEND": "path.to.new.custom.backend.RedisCache",
        # other parameters and options
    },
}

Results

In [1]: from django.core.cache import cache

In [2]: cache.get("test")

In [3]: cache.set("test", "Foo", 30)

In [4]: cache.get("test")
Out[4]: 'Foo'

In [5]: cache.ttl("test")
Out[5]: 21

In [6]: cache.ttl("test")
Out[6]: 19

In [7]: cache.ttl("any-key")
Out[7]: -2