For upr flow control if we have any room in our buffer we should always send the item

For large items it is possible that we might send a very small item followed by a very large item. On the consumer side of the connection we also might wait for a certain amount of bytes to be processed before sending an ack. As a result we can get into a situation where we have sent less than the threshold needed for an ack. The easiest way to resolve this problem is to always send items from the producer until the buffer is full even if this means sending more data than fits in the buffer.