| /*
|
| * 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.ArrayList;
|
| import java.util.List;
|
| import java.util.concurrent.ConcurrentHashMap;
|
| import java.util.concurrent.ConcurrentMap;
|
|
|
| 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 final ConcurrentMap<String, AtomicPositiveInteger> weightSequences = new ConcurrentHashMap<String, AtomicPositiveInteger>();
|
| |
| protected <T> Invoker<T> doSelect(List<Invoker<T>> invokers, 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); |
| } |
| |
| } |