Dubbo之——几种负载均衡算法

转载请注明出处：http://blog.csdn.net/l1028386804/article/details/72512794

1、RandomLoadBalance算法

public class RandomLoadBalance extends AbstractLoadBalance {    public static final String NAME = "random";    private final Random random = new Random();    protected <T> Invoker<T> doSelect(List<Invoker<T>> invokers, URL url, Invocation invocation) {        int length = invokers.size(); // 总个数        int totalWeight = 0; // 总权重        boolean sameWeight = true; // 权重是否都一样        for (int i = 0; i < length; i++) {            int weight = getWeight(invokers.get(i), invocation);            totalWeight += weight; // 累计总权重            if (sameWeight && i > 0                    && weight != getWeight(invokers.get(i - 1), invocation)) {                sameWeight = false; // 计算所有权重是否一样            }        }        if (totalWeight > 0 && ! sameWeight) {            // 如果权重不相同且权重大于0则按总权重数随机            int offset = random.nextInt(totalWeight);            // 并确定随机值落在哪个片断上            for (int i = 0; i < length; i++) {                offset -= getWeight(invokers.get(i), invocation);                if (offset < 0) {                    return invokers.get(i);                }            }        }        // 如果权重相同或权重为0则均等随机        return invokers.get(random.nextInt(length));    }}

2、RoundRobinLoadBalance算法

public class RoundRobinLoadBalance extends AbstractLoadBalance {    public static final String NAME = "roundrobin";         private final ConcurrentMap<String, AtomicPositiveInteger> sequences = new ConcurrentHashMap<String, AtomicPositiveInteger>();    private final ConcurrentMap<String, AtomicPositiveInteger> weightSequences = new ConcurrentHashMap<String, AtomicPositiveInteger>();    protected <T> Invoker<T> doSelect(List<Invoker<T>> invokers, URL url, Invocation invocation) {        String key = invokers.get(0).getUrl().getServiceKey() + "." + invocation.getMethodName();        int length = invokers.size(); // 总个数        int maxWeight = 0; // 最大权重        int minWeight = Integer.MAX_VALUE; // 最小权重        for (int i = 0; i < length; i++) {            int weight = getWeight(invokers.get(i), invocation);            maxWeight = Math.max(maxWeight, weight); // 累计最大权重            minWeight = Math.min(minWeight, weight); // 累计最小权重        }        if (maxWeight > 0 && minWeight < maxWeight) { // 权重不一样            AtomicPositiveInteger weightSequence = weightSequences.get(key);            if (weightSequence == null) {                weightSequences.putIfAbsent(key, new AtomicPositiveInteger());                weightSequence = weightSequences.get(key);            }            int currentWeight = weightSequence.getAndIncrement() % maxWeight;            List<Invoker<T>> weightInvokers = new ArrayList<Invoker<T>>();            for (Invoker<T> invoker : invokers) { // 筛选权重大于当前权重基数的Invoker                if (getWeight(invoker, invocation) > currentWeight) {                    weightInvokers.add(invoker);                }            }            int weightLength = weightInvokers.size();            if (weightLength == 1) {                return weightInvokers.get(0);            } else if (weightLength > 1) {                invokers = weightInvokers;                length = invokers.size();            }        }        AtomicPositiveInteger sequence = sequences.get(key);        if (sequence == null) {            sequences.putIfAbsent(key, new AtomicPositiveInteger());            sequence = sequences.get(key);        }        // 取模轮循        return invokers.get(sequence.getAndIncrement() % length);    }}

3、LeastActionLoadBalance算法

public class LeastActiveLoadBalance extends AbstractLoadBalance {    public static final String NAME = "leastactive";        private final Random random = new Random();    protected <T> Invoker<T> doSelect(List<Invoker<T>> invokers, URL url, Invocation invocation) {        int length = invokers.size(); // 总个数        int leastActive = -1; // 最小的活跃数        int leastCount = 0; // 相同最小活跃数的个数        int[] leastIndexs = new int[length]; // 相同最小活跃数的下标        int totalWeight = 0; // 总权重        int firstWeight = 0; // 第一个权重，用于于计算是否相同        boolean sameWeight = true; // 是否所有权重相同        for (int i = 0; i < length; i++) {        Invoker<T> invoker = invokers.get(i);            int active = RpcStatus.getStatus(invoker.getUrl(), invocation.getMethodName()).getActive(); // 活跃数            int weight = invoker.getUrl().getMethodParameter(invocation.getMethodName(), Constants.WEIGHT_KEY, Constants.DEFAULT_WEIGHT); // 权重            if (leastActive == -1 || active < leastActive) { // 发现更小的活跃数，重新开始                leastActive = active; // 记录最小活跃数                leastCount = 1; // 重新统计相同最小活跃数的个数                leastIndexs[0] = i; // 重新记录最小活跃数下标                totalWeight = weight; // 重新累计总权重                firstWeight = weight; // 记录第一个权重                sameWeight = true; // 还原权重相同标识            } else if (active == leastActive) { // 累计相同最小的活跃数                leastIndexs[leastCount ++] = i; // 累计相同最小活跃数下标                totalWeight += weight; // 累计总权重                // 判断所有权重是否一样                if (sameWeight && i > 0                         && weight != firstWeight) {                    sameWeight = false;                }            }        }        // assert(leastCount > 0)        if (leastCount == 1) {            // 如果只有一个最小则直接返回            return invokers.get(leastIndexs[0]);        }        if (! sameWeight && totalWeight > 0) {            // 如果权重不相同且权重大于0则按总权重数随机            int offsetWeight = random.nextInt(totalWeight);            // 并确定随机值落在哪个片断上            for (int i = 0; i < leastCount; i++) {                int leastIndex = leastIndexs[i];                offsetWeight -= getWeight(invokers.get(leastIndex), invocation);                if (offsetWeight <= 0)                    return invokers.get(leastIndex);            }        }        // 如果权重相同或权重为0则均等随机        return invokers.get(leastIndexs[random.nextInt(leastCount)]);    }}

4、ConsistentHashLoadBalance算法

public class ConsistentHashLoadBalance extends AbstractLoadBalance {    private final ConcurrentMap<String, ConsistentHashSelector<?>> selectors = new ConcurrentHashMap<String, ConsistentHashSelector<?>>();    @SuppressWarnings("unchecked")    @Override    protected <T> Invoker<T> doSelect(List<Invoker<T>> invokers, URL url, Invocation invocation) {        String key = invokers.get(0).getUrl().getServiceKey() + "." + invocation.getMethodName();        int identityHashCode = System.identityHashCode(invokers);        ConsistentHashSelector<T> selector = (ConsistentHashSelector<T>) selectors.get(key);        if (selector == null || selector.getIdentityHashCode() != identityHashCode) {            selectors.put(key, new ConsistentHashSelector<T>(invokers, invocation.getMethodName(), identityHashCode));            selector = (ConsistentHashSelector<T>) selectors.get(key);        }        return selector.select(invocation);    }    private static final class ConsistentHashSelector<T> {    private final TreeMap<Long, Invoker<T>> virtualInvokers;    private final int                       replicaNumber;    private final int                       identityHashCode;    private final int[]                     argumentIndex;  public ConsistentHashSelector(List<Invoker<T>> invokers, String methodName, int identityHashCode) {            this.virtualInvokers = new TreeMap<Long, Invoker<T>>();            this.identityHashCode = System.identityHashCode(invokers);            URL url = invokers.get(0).getUrl();            this.replicaNumber = url.getMethodParameter(methodName, "hash.nodes", 160);            String[] index = Constants.COMMA_SPLIT_PATTERN.split(url.getMethodParameter(methodName, "hash.arguments", "0"));            argumentIndex = new int[index.length];            for (int i = 0; i < index.length; i ++) {                argumentIndex[i] = Integer.parseInt(index[i]);            }            for (Invoker<T> invoker : invokers) {                for (int i = 0; i < replicaNumber / 4; i++) {                    byte[] digest = md5(invoker.getUrl().toFullString() + i);                    for (int h = 0; h < 4; h++) {                        long m = hash(digest, h);                        virtualInvokers.put(m, invoker);                    }                }            }        }        public int getIdentityHashCode() {            return identityHashCode;        }        public Invoker<T> select(Invocation invocation) {            String key = toKey(invocation.getArguments());            byte[] digest = md5(key);            Invoker<T> invoker = sekectForKey(hash(digest, 0));            return invoker;        }        private String toKey(Object[] args) {            StringBuilder buf = new StringBuilder();            for (int i : argumentIndex) {                if (i >= 0 && i < args.length) {                    buf.append(args[i]);                }            }            return buf.toString();        }        private Invoker<T> sekectForKey(long hash) {            Invoker<T> invoker;            Long key = hash;            if (!virtualInvokers.containsKey(key)) {                SortedMap<Long, Invoker<T>> tailMap = virtualInvokers.tailMap(key);                if (tailMap.isEmpty()) {                    key = virtualInvokers.firstKey();                } else {                    key = tailMap.firstKey();                }            }            invoker = virtualInvokers.get(key);            return invoker;        }        private long hash(byte[] digest, int number) {            return (((long) (digest[3 + number * 4] & 0xFF) << 24)                    | ((long) (digest[2 + number * 4] & 0xFF) << 16)                    | ((long) (digest[1 + number * 4] & 0xFF) << 8)                     | (digest[0 + number * 4] & 0xFF))                     & 0xFFFFFFFFL;        }        private byte[] md5(String value) {            MessageDigest md5;            try {                md5 = MessageDigest.getInstance("MD5");            } catch (NoSuchAlgorithmException e) {                throw new IllegalStateException(e.getMessage(), e);            }            md5.reset();            byte[] bytes = null;            try {                bytes = value.getBytes("UTF-8");            } catch (UnsupportedEncodingException e) {                throw new IllegalStateException(e.getMessage(), e);            }            md5.update(bytes);            return md5.digest();        }    }}