tokenBucket: incorrect count of issued when refill

[rschio]

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)

[reugn]

@rschio thanks.