import net.floodlightcontroller.debugcounter.DebugCounterResource; //导入依赖的package包/类
/**
 * Compute the maximum number of flows to be reconciled.
 *
 * It computes the packetIn increment from the counter values in
 * the counter store;
 * Then computes the rate based on the elapsed time
 * from the last query;
 * Then compute the max flow reconcile rate by subtracting the packetIn
 * rate from the hard-coded max system rate.
 * If the system rate is reached or less than MIN_FLOW_RECONCILE_PER_SECOND,
 * set the maximum flow reconcile rate to the MIN_FLOW_RECONCILE_PER_SECOND
 * to prevent starvation.
 * Then convert the rate to an absolute number for the
 * FLOW_RECONCILE_PERIOD.
 * @return
 */
protected int getCurrentCapacity() {
	int minFlows = MIN_FLOW_RECONCILE_PER_SECOND * FLOW_RECONCILE_DELAY_MILLISEC / 1000;

	List<DebugCounterResource> contCtrRsrcList = debugCounterService.getModuleCounterValues(Controller.class.getName());
	for (DebugCounterResource dcr : contCtrRsrcList) {
		if (dcr.getCounterHierarchy().equals("packet-in")) {
			ctrPacketInRsrc = dcr;
			break;
		}
	}

	// If no packetInCounter, then there shouldn't be any flow.
	if (ctrPacketInRsrc == null || ctrPacketInRsrc.getCounterValue() == null || ctrPacketInRsrc.getCounterValue() == 0) {
		logger.debug("counter {} doesn't exist", ctrPacketInRsrc);
		return minFlows;
	}

	// We're the first packet_in
	if (lastPacketInCounter.getCounterValue() == 0) {
		logger.debug("First time get the count for {}", lastPacketInCounter);
		return minFlows;
	}

	int pktInRate = getPktInRate(ctrPacketInRsrc, new Date());

	// Update the last packetInCounter
	lastPacketInCounter.reset();
	int capacity = minFlows;
	if ((pktInRate + MIN_FLOW_RECONCILE_PER_SECOND) <=
			MAX_SYSTEM_LOAD_PER_SECOND) {
		capacity = (MAX_SYSTEM_LOAD_PER_SECOND - pktInRate)
				* FLOW_RECONCILE_DELAY_MILLISEC / 1000;
	}

	if (logger.isTraceEnabled()) {
		logger.trace("Capacity is {}", capacity);
	}
	return capacity;
}
 

import net.floodlightcontroller.debugcounter.DebugCounterResource; //导入依赖的package包/类
protected int getPktInRate(DebugCounterResource newCnt, Date currentTime) {
	if (newCnt == null ||
			newCnt.getCounterLastModified() == null ||
			newCnt.getCounterValue() == null) {
		return 0;
	}

	// Somehow the system time is messed up. return max packetIn rate
	// to reduce the system load.
	if (newCnt.getCounterLastModified() < lastPacketInCounter.getLastModified()) {
		logger.debug("Time is going backward. new {}, old {}",
				newCnt.getCounterLastModified(),
				lastPacketInCounter.getLastModified());
		return MAX_SYSTEM_LOAD_PER_SECOND;
	}

	long elapsedTimeInSecond = (currentTime.getTime() - lastPacketInCounter.getLastModified()) / 1000;
	if (elapsedTimeInSecond == 0) {
		// This should never happen. Check to avoid division by zero.
		return 0;
	}

	long diff = 0;
	long newValue = newCnt.getCounterValue().longValue();
	long oldValue = lastPacketInCounter.getCounterValue();
	if (newValue < oldValue) {
		// Roll over event
		diff = Long.MAX_VALUE - oldValue + newValue;
	} else {
		diff = newValue - oldValue;
	}

	return (int)(diff/elapsedTimeInSecond);
}