public void setRingBufferSize(int ringBufferSize) {
        Assert.isTrue(ringBufferSize > 0 && Integer.bitCount(ringBufferSize) == 1,
                "'ringBufferSize' must be a power of 2 ");
        this.ringBufferSize = ringBufferSize;
    }
The size of the RingBuffer, must be a power of 2.  Default is 8192.

@param ringBufferSize size of the RingBuffer.
spring-xd-reactor/src/main/java/org/springframework/xd/reactor/AbstractReactorMessageHandler.java