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A set of performant rate limiters for Go

Home Page: https://pkg.go.dev/github.com/reugn/equalizer

License: MIT License

Go 100.00%

api rate-limiter rate quotas rate-limiting throttler throttling throttle tokenbucket sliding-window

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equalizer's Issues

tokenBucket: incorrect count of issued when refill

equalizer/token_bucket.go

Lines 66 to 79 in d5d1ad1

    
           // refill refills the token bucket. 
        
           func (tb *tokenBucket) refill() { 
        
           	issued := atomic.LoadInt32(&tb.issued) 
        
           	atomic.StoreInt32(&tb.issued, 0) 
        
           	tb.fillTokenBucket(int(issued)) 
        
           } 
        
           // Ask requires a permit. 
        
           // It is a non blocking call, returns true or false. 
        
           func (tb *TokenBucket) Ask() bool { 
        
           	select { 
        
           	case <-tb.t.permits: 
        
           		atomic.AddInt32(&tb.t.issued, 1) 
        
           		return true

A token can be issued between line 68 and 69 and then it will lead to a incorrect issued count and decrease the bucket real capacity.

Example:
refill() and Ask() executes concurrently then:
line 68 executes
line 77 and 78 executes
line 69 and 70 executes

Solution:
issued := atomic.SwapInt32(&tb.issued, 0)

Maybe consider context.Context for blocking Take()

Thanks for providing this simple library!
One thing I noted is that Take() cannot be interrupted if it takes very long (some api limits are very strict), so for example it will considerably delay aborting an action. Could you maybe consider to provide a Take operation which can be interrupted through a context object? That would be a great improvement!

reugn / equalizer Goto Github PK

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equalizer's Issues

tokenBucket: incorrect count of issued when refill

Maybe consider context.Context for blocking Take()

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	// refill refills the token bucket.
	func (tb *tokenBucket) refill() {
	issued := atomic.LoadInt32(&tb.issued)
	atomic.StoreInt32(&tb.issued, 0)
	tb.fillTokenBucket(int(issued))
	}

	// Ask requires a permit.
	// It is a non blocking call, returns true or false.
	func (tb *TokenBucket) Ask() bool {
	select {
	case <-tb.t.permits:
	atomic.AddInt32(&tb.t.issued, 1)
	return true