/* * Copyright 1999-2011 Alibaba Group. * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package com.alibaba.dubbo.rpc.cluster.loadbalance; import java.util.LinkedHashMap; import java.util.List; import java.util.Map; import java.util.concurrent.ConcurrentHashMap; import java.util.concurrent.ConcurrentMap; import com.alibaba.dubbo.common.URL; import com.alibaba.dubbo.common.utils.AtomicPositiveInteger; import com.alibaba.dubbo.rpc.Invocation; import com.alibaba.dubbo.rpc.Invoker; /** * Round robin load balance. * * @author qian.lei * @author william.liangf */ public class RoundRobinLoadBalance extends AbstractLoadBalance { public static final String NAME = "roundrobin"; private final ConcurrentMap<String, AtomicPositiveInteger> sequences = new ConcurrentHashMap<String, AtomicPositiveInteger>(); private static final class IntegerWrapper { public IntegerWrapper(int value) { this.value = value; } private int value; public int getValue() { return value; } public void setValue(int value) { this.value = value; } public void decrement() { this.value--; } } 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 final LinkedHashMap<Invoker<T>, IntegerWrapper> invokerToWeightMap = new LinkedHashMap<Invoker<T>, IntegerWrapper>(); int weightSum = 0; 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 (weight > 0) { invokerToWeightMap.put(invokers.get(i), new IntegerWrapper(weight)); weightSum += weight; } } AtomicPositiveInteger sequence = sequences.get(key); if (sequence == null) { sequences.putIfAbsent(key, new AtomicPositiveInteger()); sequence = sequences.get(key); } int currentSequence = sequence.getAndIncrement(); if (maxWeight > 0 && minWeight < maxWeight) { // 权重不一样 int mod = currentSequence % weightSum; for (int i = 0; i < maxWeight; i++) { for (Map.Entry<Invoker<T>, IntegerWrapper> each : invokerToWeightMap.entrySet()) { final Invoker<T> k = each.getKey(); final IntegerWrapper v = each.getValue(); if (mod == 0 && v.getValue() > 0) { return k; } if (v.getValue() > 0) { v.decrement(); mod--; } } } } // 取模轮循 return invokers.get(currentSequence % length); } }