| /*
|
| * 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.List; |
| import java.util.Random; |
| |
| import com.alibaba.dubbo.common.Extension; |
| import com.alibaba.dubbo.rpc.Invoker; |
| import com.alibaba.dubbo.rpc.Invocation; |
| |
| /** |
| * random load balance. |
| * |
| * @author qianlei |
| * @author william.liangf |
| */ |
| @Extension(RandomLoadBalance.NAME) |
| 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, 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++) { |
| // 获取权重 |
| int weight = getWeight(invokers.get(i), invocation); |
| // 累计总权重 |
| totalWeight += weight; |
| // 判断所有权重是否一样 |
| if (sameWeight && i > 0 |
| && weight != getWeight(invokers.get(i - 1), invocation)) { |
| sameWeight = false; |
| } |
| } |
| 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 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)); |
| } |
| } |