FastAPICache.Clear(namespace...) does not work with custom key_builder

[Nickopusan13]

Hello,
I'm having an issue with FastAPICache.clear() when using a custom key_builder.

The caching itself works perfectly:

@cache(expire=300, key_builder=create_client_key_builder("clients:single"))
async def get_single_client(...):
    ...

The key appears correctly in Redis like this:

clients:single:user:3:client_id:3:no-params

But when I try to clear it, nothing happens:

await FastAPICache.clear(
    namespace=f"clients:single:user:{current_user.id}:client_id:{client_id}:no-params"
)

Even though the string I'm passing is exactly the same as the key in Redis.

Right now I'm doing this and it works:

await redis_client.delete(
    f"clients:single:user:{current_user.id}:client_id:{client_id}:no-params"
)

Key Builder

def create_client_key_builder(namespace: str):
    def builder(func, *args, **kwargs):
        request = kwargs.get("request")
        current_user = getattr(request.state, "user", None)
        user_id = getattr(current_user, "id", "anonymous")
        client_id = kwargs.get("client_id") or request.path_params.get("client_id")
        query_params = request.url.query or "no-params"
        return f"{namespace}:user:{user_id}:client_id:{client_id}:{query_params}"
    return builder

[hosamk92]

Hello @Nickopusan13

I don't think this is a bug, clear(namespace=...) works a bit differently than it might seem. It doesn't match your literal key string, it clears based on a prefix + namespace pattern, which is meant for clearing groups of keys that share a generated prefix, like when you're using the default key builder.

Since your custom key_builder returns the exact literal key, the simpler fix is to clear it directly by key instead:

await FastAPICache.clear(
    key=f"clients:single:user:{current_user.id}:client_id:{client_id}:no-params"
)

That should give you the same result as your redis_client.delete(...) workaround.

If you would like to use it with namespace you could use the following:

await FastAPICache.clear(namespace="clients:single:") // clear all keys stored by the custom builder as it uses this namespace

// or use this 
await FastAPICache.clear(namespace="clients:single:user:3:") // to clear all keys for specific user

When using namespace in clear it woul clear all keys that starts by the namespace.