| /* |
| * Licensed to the Apache Software Foundation (ASF) under one or more |
| * contributor license agreements. See the NOTICE file distributed with |
| * this work for additional information regarding copyright ownership. |
| * The ASF licenses this file to You 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 com.alibaba.dubbo.common.URL; |
| import com.alibaba.dubbo.rpc.Invocation; |
| import com.alibaba.dubbo.rpc.Invoker; |
| |
| import java.util.List; |
| import java.util.Random; |
| |
| /** |
| * random load balance. |
| * |
| */ |
| public class RandomLoadBalance extends AbstractLoadBalance { |
| |
| public static final String NAME = "random"; |
| |
| private final Random random = new Random(); |
| |
| @Override |
| protected <T> Invoker<T> doSelect(List<Invoker<T>> invokers, URL url, Invocation invocation) { |
| int length = invokers.size(); // Number of invokers |
| int totalWeight = 0; // The sum of weights |
| boolean sameWeight = true; // Every invoker has the same weight? |
| for (int i = 0; i < length; i++) { |
| int weight = getWeight(invokers.get(i), invocation); |
| totalWeight += weight; // Sum |
| if (sameWeight && i > 0 |
| && weight != getWeight(invokers.get(i - 1), invocation)) { |
| sameWeight = false; |
| } |
| } |
| if (totalWeight > 0 && !sameWeight) { |
| // If (not every invoker has the same weight & at least one invoker's weight>0), select randomly based on totalWeight. |
| int offset = random.nextInt(totalWeight); |
| // Return a invoker based on the random value. |
| for (int i = 0; i < length; i++) { |
| offset -= getWeight(invokers.get(i), invocation); |
| if (offset < 0) { |
| return invokers.get(i); |
| } |
| } |
| } |
| // If all invokers have the same weight value or totalWeight=0, return evenly. |
| return invokers.get(random.nextInt(length)); |
| } |
| |
| } |