🤗 [Question]: limiter supports dynamic setting of “Max” parameter

[zhangyongding]

Question Description

limiter only supports setting a fixed max value. Can a function be used to obtain a max value
example:

func(c *fiber.Ctx) int 
or
func(key string) int

Code Snippet (optional)

No response

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• I agree to follow Fiber's Code of Conduct.
• I have checked for existing issues that describe my questions prior to opening this one.
• I understand that improperly formatted questions may be closed without explanation.

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[ReneWerner87]

@zhangyongding can you please describe in more detail what you want to achieve and, if necessary, provide an example

[zhangyongding]

add in middleware\limiter\config.go

type Config struct {
	...

	// MaxGenerator allows you to generate custom max, by default nil is used
	//
	// Default: nil
	MaxGenerator func(fiber.Ctx) int

	...
}

or

type Config struct {
	...

	// MaxGenerator allows you to generate custom max, by default nil is used
	//
	// Default: nil
	MaxGenerator func(key string) int
	
	...
}

example: middleware\limiter\limiter_fixed.go

// New creates a new fixed window middleware handler
func (FixedWindow) New(cfg Config) fiber.Handler {
	var (
		// Limiter variables
		mux        = &sync.RWMutex{}
		expiration = uint64(cfg.Expiration.Seconds())
	)

	// Create manager to simplify storage operations ( see manager.go )
	manager := newManager(cfg.Storage)

	// Update timestamp every second
	utils.StartTimeStampUpdater()

	// Return new handler
	return func(c fiber.Ctx) error {
		// Don't execute middleware if Next returns true
		if cfg.Next != nil && cfg.Next(c) {
			return c.Next()
		}

		// Get key from request
		key := cfg.KeyGenerator(c)

		// Get max from request or config
		max := cfg.Max
		if cfg.MaxGenerator != nil {
			max = cfg.MaxGenerator(c) // or max = cfg.MaxGenerator(key)
		}

		if max == 0 {
			return c.Next()
		}

		// Lock entry
		mux.Lock()

		// Get entry from pool and release when finished
		e := manager.get(key)

		// Get timestamp
		ts := uint64(utils.Timestamp())

		// Set expiration if entry does not exist
		if e.exp == 0 {
			e.exp = ts + expiration
		} else if ts >= e.exp {
			// Check if entry is expired
			e.currHits = 0
			e.exp = ts + expiration
		}

		// Increment hits
		e.currHits++

		// Calculate when it resets in seconds
		resetInSec := e.exp - ts

		// Set how many hits we have left
		remaining := max - e.currHits

		// Update storage
		manager.set(key, e, cfg.Expiration)

		// Unlock entry
		mux.Unlock()

		// Check if hits exceed the max
		if remaining < 0 {
			// Return response with Retry-After header
			// https://tools.ietf.org/html/rfc6584
			c.Set(fiber.HeaderRetryAfter, strconv.FormatUint(resetInSec, 10))

			// Call LimitReached handler
			return cfg.LimitReached(c)
		}

		// Continue stack for reaching c.Response().StatusCode()
		// Store err for returning
		err := c.Next()

		// Check for SkipFailedRequests and SkipSuccessfulRequests
		if (cfg.SkipSuccessfulRequests && c.Response().StatusCode() < fiber.StatusBadRequest) ||
			(cfg.SkipFailedRequests && c.Response().StatusCode() >= fiber.StatusBadRequest) {
			// Lock entry
			mux.Lock()
			e = manager.get(key)
			e.currHits--
			remaining++
			manager.set(key, e, cfg.Expiration)
			// Unlock entry
			mux.Unlock()
		}

		// We can continue, update RateLimit headers
		c.Set(xRateLimitLimit, strconv.Itoa(max))
		c.Set(xRateLimitRemaining, strconv.Itoa(remaining))
		c.Set(xRateLimitReset, strconv.FormatUint(resetInSec, 10))

		return err
	}
}

[ReneWerner87]

I'm not sure what use case this is intended for
probably for the usecase where you want to manage different accounts with different rate limits

[zhangyongding]

Yes, I want to manage different accounts with different rate limits

[zhangyongding]

Does v2 accept PR?

[ReneWerner87]

Does v2 accept PR?

no, only v3 accept new features

[luk3skyw4lker]

@zhangyongding are you working on a PR? If not I could do it and send the PR today still