gudegg commented on issue #2578: The current RoundRobinLoadBalance implementation performance is not satisfactory URL: https://github.com/apache/incubator-dubbo/issues/2578#issuecomment-425648009 @kimmking The above implementation is also very bad when the greatest common divisor is 1. This performance will be much better. Help me to see if there are any problems. thx! ```java 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> indexSeqs = new ConcurrentHashMap<String, AtomicPositiveInteger>(); @Override 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(); // Number of invokers int maxWeight = 0; // The maximum weight int minWeight = Integer.MAX_VALUE; // The minimum weight final List<Invoker<T>> invokerToWeightList = new ArrayList<>(); for (int i = 0; i < length; i++) { int weight = getWeight(invokers.get(i), invocation); maxWeight = Math.max(maxWeight, weight); // Choose the maximum weight minWeight = Math.min(minWeight, weight); // Choose the minimum weight if (weight > 0) { invokerToWeightList.add(invokers.get(i)); } } AtomicPositiveInteger sequence = sequences.get(key); if (sequence == null) { sequences.putIfAbsent(key, new AtomicPositiveInteger()); sequence = sequences.get(key); } AtomicPositiveInteger indexSeq = indexSeqs.get(key); if (indexSeq == null) { indexSeqs.putIfAbsent(key, new AtomicPositiveInteger(-1)); indexSeq = indexSeqs.get(key); } if (maxWeight > 0 && minWeight < maxWeight) { length = invokerToWeightList.size(); while (true) { int index = indexSeq.incrementAndGet() % length; int currentWeight = sequence.get() % maxWeight; if (index == 0) { currentWeight = sequence.incrementAndGet() % maxWeight; } if (getWeight(invokerToWeightList.get(index), invocation) > currentWeight) { return invokerToWeightList.get(index); } } } // Round robin return invokers.get(sequence.incrementAndGet() % length); } } ```
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