protected function changeQueueCount($queueCounter)
    {
        if ($queueCounter < 0) {
            $queueCounter = 0;
        }
        $this->_poolClientQueueCounter = $queueCounter;
        //Automatically change client state to `ClientInterface::CLIENT_POOL_STATE_READY` on empty queue
        if ($this->_poolClientQueueCounter === 0 && $this->_poolClientState === PoolClientInterface::CLIENT_POOL_STATE_BUSY) {
            $this->changeState(PoolClientInterface::CLIENT_POOL_STATE_READY);
        } elseif ($this->_poolClientQueueCounter > 0 && $this->_poolClientState === PoolClientInterface::CLIENT_POOL_STATE_READY) {
            $this->changeState(PoolClientInterface::CLIENT_POOL_STATE_BUSY);
        }
        $this->emit(PoolClientInterface::CLIENT_POOL_EVENT_CHANGE_QUEUE, [$queueCounter]);
    }