Redis cache backend doesn't allow storing bool values

[Jeremy Lainé]

The following code raises an exception: redis.exceptions.DataError: Invalid input of type: 'bool'. Convert to a bytes, string, int or float first.

from django.core.cache import cache
cache.set("foo", True)

This contradicts the documentation which states that any data type supported by pickle can be stored to the cache.

The root cause seems to be because instances of int are special-cased and not send through pickle, but redis-py cannot send booleans to redis:

​https://github.com/django/django/blob/2f73e5406d54cb8945e187eff302a3a3373350be/django/core/cache/backends/redis.py#L14

What was the rationale behind the int special-case? django-redis for instance consistently sends all data through pickle.

[Mariusz Felisiak]

Thanks for report! It should be enough to special-case bool, e.g.

django/core/cache/backends/redis.py

@@ -11 +11 @@
 
 class RedisSerializer(PickleSerializer):
     def dumps(self, obj):
-        if isinstance(obj, int):
+        if isinstance(obj, int) and not isinstance(obj, bool):
             return obj
         return super().dumps(obj)
 

Would you like to prepare a patch?

What was the rationale behind the int special-case? django-redis for instance consistently sends all data through pickle.

We do this to have better atomicity of incr() and decr() operations (see ​discussion).

[Jeremy Lainé]

Thanks for the reply and the link to the discussion. I'm assigning myself to the ticket as I'd be happy to prepare a patch and corresponding test.

Regarding the proposed fix, it feels like we're just moving the problem as I'd expect similar issues with an user-defined subclasses of int. Would it be acceptable to do:

django/core/cache/backends/redis.py

@@ -11 +11 @@
 
 class RedisSerializer(PickleSerializer):
     def dumps(self, obj):
-        if isinstance(obj, int):
+        if type(obj) is int:
             return obj
         return super().dumps(obj)
 

[Mariusz Felisiak]

Replying to Jeremy Lainé:

Thanks for the reply and the link to the discussion. I'm assigning myself to the ticket as I'd be happy to prepare a patch and corresponding test.

Regarding the proposed fix, it feels like we're just moving the problem as I'd expect similar issues with an user-defined subclasses of int. Would it be acceptable to do:

django/core/cache/backends/redis.py

@@ -11 +11 @@
 
 class RedisSerializer(PickleSerializer):
     def dumps(self, obj):
-        if isinstance(obj, int):
+        if type(obj) is int:
             return obj
         return super().dumps(obj)
 

Yes, looks good, a small comment could de helpful.

[Jeremy Lainé]

I've submitted a PR which includes a simple unit test on serialization. I checked the tests pass by running it locally with a configured Redis cache, I'm not sure if CI executes backend-specific tests though.

[Claude Paroz]

​PR

[Mariusz Felisiak <felisiak.mariusz@…>]

In c7902612:

Refs #33361 -- Added Added DummyCache.set() test for boolean values.

[Mariusz Felisiak <felisiak.mariusz@…>]

In 2f33217:

Fixed #33361 -- Fixed Redis cache backend crash on booleans.

[Mariusz Felisiak <felisiak.mariusz@…>]

In 3b03bce1:

[4.0.x] Fixed #33361 -- Fixed Redis cache backend crash on booleans.

Backport of 2f33217ea2cad688040dd6044cdda946c62e5b65 from main