Question about precise-memory-ratelimit

[Nebulizer1213]

Description

Is there a way to get the request and response from inside of the increment function, so I can get the max if they use the ValueDeterminingMiddleWare?

I have this, but it only works if they use a number for max

        let user = this.hits[key]
        let reset = calculateNextResetTime(this.windowMs, user)
        if (user.ts + this.windowMs <= time()) {
            user.hits = 0
        }
        if (user.hits > this.max) {
            return {
                totalHits: user.hits,
                resetTime: reset
            }
        }
        user.hits++
        user.ts = time()
        this.hits[key] = user
        return {
            totalHits: user.hits,
            resetTime: reset
        }

Library version

6.5.1

Node version

v18.4.0

Typescript version (if you are using it)

v4.7.4

Module system

ESM

[gamemaker1]

You could get the max (function or number) from the options passed in the init function:

So in your init function you could add the following line:

const getMax = typeof options.max === 'function'
	? options.max(request, response)
	: options.max
this.max = await getMax

And then remove the same line from your constructor.

[nfriedly]

@gamemaker1 I don't think that would work, as request and response aren't available when the init function is called.

@Nebulizer1213 I think this would require a change to the store API, to either pass in the request/response, or else the calculated max value in an extra argument. If we were going to pass in req/res, it would probably make sense to calculate max and set it on the req ahead of time. Let me think about that a bit more...

Can you give me more context on what ValueDeterminingMiddleWare is? Why would increment need to know the max value?

[Nebulizer1213]

@nfriedly I need the max in the incr function because if the user's request exceeds the max, the timestamp for the user should not change.

    if (user.hits > this.max) {
            return {
                totalHits: user.hits,
                resetTime: reset
            }
        }
        user.hits++
        user.ts = time()

[nfriedly]

Hum.. it looks like the redis and mongo stores handle this via an option - the reset time is based either on the first hit or the most recent hit. I don't think any store counts the reset time from the last successful hit.

Would something like that work for your use-case?

[Nebulizer1213]

I'm pretty sure the other stores use the fixed window algorithm by setting an expiry on the first request. This would not work for me because I use the token bucket algorithm.

[nfriedly]

Ok, I've been thinking about this. I think we should just add max as an extra param on the end of the increment call. When max is a function, we should execute it within express-rate-limit and pass along the integer value, not the function.

I don't think this will break any existing stores, but I'd like to check to be sure. If necessary, we could add a way for stores to opt into this behavior.