Attempting to use RateLimitLayer in tower::limit::rate on Axum server not working

[khalludi]

Long story short, I'm trying to extend an existing rate limiter. I copied the code exactly and made only one change in rate_limit/service.rs lines 21-33 where I add a clone implementation to RateLimit. The change was needed because all layers need to be clonable to add to the Axum router's layer() func (see main.rs).

The problem is, when I try to modify the struct's field in the Service's call() method (see here), the state is not updating. In the output below, you can see that the local state inside the call() method is updated ('New Until' tag), however the global state inside the struct is not updated (same 'Until' time tag on each request).

My question is, what should I be doing so that I can modify the state field (or any field) within the call() method of a service? Alternatively, would creating a similar layer in Axum be the correct way for developing layers?

Output:

Now: Instant { t: 414379.3779662s }
Until: Instant { t: 414376.774569s }
Rem: 5
New Until: Instant { t: 414439.3779662s }
-------
Now: Instant { t: 414381.2349382s }
Until: Instant { t: 414376.774569s }
Rem: 5
New Until: Instant { t: 414441.2349382s }
-------
Now: Instant { t: 414382.1941313s }
Until: Instant { t: 414376.774569s }
Rem: 5
New Until: Instant { t: 414442.1941313s }
-------
Now: Instant { t: 414383.3867334s }
Until: Instant { t: 414376.774569s }
Rem: 5
New Until: Instant { t: 414443.3867334s }

Github reproducible code: https://github.com/khalludi/token-bucket-rl

[davidpdrsn]

There is a reason tower's rate limiting middleware doesn't implement Clone. By doing what you're doing your essentially bypassing the limiting by cloning everything. The clones don't actually share the underlying service, or the bookkeeping for how many requests have been sent.

I answered a similar question previously. See #987

[psionic-k]

Seems like the better approach is to implement clone on an outer struct that hides the thread safety of an inner rate limit implementation.