Fixed window strategy using mongodb storage not working

[bertytobing]

Fixed window strategy using mongodb storage not working. The expireAt always use moving window strategy.

def incr(
        self, key: str, expiry: int, elastic_expiry: bool = False, amount: int = 1
    ) -> int:
        """
        increments the counter for a given rate limit key

        :param key: the key to increment
        :param expiry: amount in seconds for the key to expire in
        :param amount: the number to increment by
        """
        expiration = datetime.datetime.utcnow() + datetime.timedelta(seconds=expiry)

        return int(
            self.counters.find_one_and_update(
                {"_id": key},
                [
                    {
                        "$set": {
                            "count": {
                                "$cond": {
                                    "if": {"$lt": ["$expireAt", "$$NOW"]},
                                    "then": amount,
                                    "else": {"$add": ["$count", amount]},
                                }
                            },
                            "expireAt": {
                                "$cond": {
                                    "if": {"$lt": ["$expireAt", "$$NOW"]},
                                    "then": expiration,
                                    "else": (
                                        expiration if elastic_expiry else "$expireAt"
                                    ),
                                }
                            },
                        }
                    },
                ],
                upsert=True,
                projection=["count"],
                return_document=self.lib.ReturnDocument.AFTER,
            )["count"]
        )

Expected Behaviour

Use strategy configuration.

Current Behaviour

https://github.com/alisaifee/limits/blob/master/limits/storage/mongodb.py#L104

Always use moving window strategy.

Steps to Reproduce

limiter = Limiter(
    key_func=lambda: get_limiter_key(),
    app=app,
    storage_uri=uri,
    enabled=True,
    strategy="fixed-window",
)

Already setting strategy but not work.

[alisaifee]

I don’t think I understand the issue clearly, could you provide a reproduction step?

[bertytobing]

I don’t think I understand the issue clearly, could you provide a reproduction step?

1. Use mongodb for storage.
2. Adopt the fixed-window strategy.
3. Set the rate limit to 2/1 minute.
4. Hit the endpoint at 00:00:55 and again at 00:00:59.
5. Hit the endpoint once more at 00:01:01. You'll receive a 429 error (indicating too many requests).

If I'm understanding correctly, the fixed-window strategy should reset the limit based on the specified period, in this case, every minute (at zero seconds). However, it currently seems to reset the limit based on the second of the first request (moving-window strategy).

[alisaifee]

Yes this is the expected behavior of the fixed window strategy is implemented (regardless of the storage type) - i.e. the window is constructed based on the second of the first hit.

[bertytobing]

Yes this is the expected behavior of the fixed window strategy is implemented (regardless of the storage type) - i.e. the window is constructed based on the second of the first hit.

So If I want to make it reset every month let's say, how to achieve that?

[alisaifee]

So If I want to make it reset every month let's say, how to achieve that?

You could call the reset method on the storage if it supports it using a scheduled job

[alisaifee]

Closing due to inactivity