code: public function setWorkerPoolSize($size) {
  		if ($this->created) {
  			throw new WorkerPoolException('Cannot set the Worker Pool Size for a created pool.');
  		}
  		$size = (int)$size;
  		if ($size <= 0) {
  			throw new \InvalidArgumentException('"' . $size . '" is not an integer greater than 0.');
  		}
  		$this->workerPoolSize = $size;
  		return $this;
  	}
docs: Sets the current size of the worker pool
  @param int $size the new worker pool size
  @return WorkerPool
  @throws \QXS\WorkerPool\WorkerPoolException in case the WorkerPool has already been created
  @throws \InvalidArgumentException in case the $size value is not within the permitted range