/*
* 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.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import com.alibaba.dubbo.common.Extension;
import com.alibaba.dubbo.common.utils.AtomicPositiveInteger;
import com.alibaba.dubbo.rpc.Invoker;
import com.alibaba.dubbo.rpc.Invocation;
/**
* Round robin load balance.
*
* @author qian.lei
* @author william.liangf
*/
@Extension(RoundRobinLoadBalance.NAME)
public class RoundRobinLoadBalance extends AbstractLoadBalance {
public static final String NAME = "roundrobin";
private final ConcurrentMap<String, AtomicPositiveInteger> sequences = new ConcurrentHashMap<String, AtomicPositiveInteger>();
protected <T> Invoker<T> doSelect(List<Invoker<T>> invokers, Invocation invocation) {
String key = invokers.get(0).getInterface().getName() + "." + invocation.getMethodName();// + System.identityHashCode(invokers);
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() % invokers.size());
}
}