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Update NextIndex function. #11

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Update NextIndex function. #11

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11 changes: 9 additions & 2 deletions main.go
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Original file line number Diff line number Diff line change
Expand Up @@ -56,7 +56,14 @@ func (s *ServerPool) AddBackend(backend *Backend) {

// NextIndex atomically increase the counter and return an index
func (s *ServerPool) NextIndex() int {
return int(atomic.AddUint64(&s.current, uint64(1)) % uint64(len(s.backends)))
for {
current := atomic.LoadUint64(&s.current)
// increase the counter in a circular fashion
next := (current + 1) % uint64(len(s.backends))
if atomic.CompareAndSwapUint64(&s.current, current, next) {
return int(next)
}
}
}

// MarkBackendStatus changes a status of a backend
Expand All @@ -75,7 +82,7 @@ func (s *ServerPool) GetNextPeer() *Backend {
next := s.NextIndex()
l := len(s.backends) + next // start from next and move a full cycle
for i := next; i < l; i++ {
idx := i % len(s.backends) // take an index by modding
idx := i % len(s.backends) // take an index by modding
if s.backends[idx].IsAlive() { // if we have an alive backend, use it and store if its not the original one
if i != next {
atomic.StoreUint64(&s.current, uint64(idx))
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