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/*
* 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 org.apache.dubbo.rpc.cluster.loadbalance;
import org.apache.dubbo.common.URL;
import org.apache.dubbo.rpc.Invocation;
import org.apache.dubbo.rpc.Invoker;
import org.apache.dubbo.rpc.RpcStatus;
import java.util.List;
import java.util.concurrent.ThreadLocalRandom;
/**
* ShortestResponseLoadBalance
*
* Filter the number of invokers with the shortest response time of success calls and count the weights and quantities of these invokers.
* If there is only one invoker, use the invoker directly;
* if there are multiple invokers and the weights are not the same, then random according to the total weight;
* if there are multiple invokers and the same weight, then randomly called.
*/
public class ShortestResponseLoadBalance extends AbstractLoadBalance {
public static final String NAME = "shortestresponse";
@Override
protected Invoker doSelect(List> invokers, URL url, Invocation invocation) {
// Number of invokers
int length = invokers.size();
// Estimated shortest response time of all invokers
long shortestResponse = Long.MAX_VALUE;
// The number of invokers having the same estimated shortest response time
int shortestCount = 0;
// The index of invokers having the same estimated shortest response time
int[] shortestIndexes = new int[length];
// the weight of every invokers
int[] weights = new int[length];
// The sum of the warmup weights of all the shortest response invokers
int totalWeight = 0;
// The weight of the first shortest response invokers
int firstWeight = 0;
// Every shortest response invoker has the same weight value?
boolean sameWeight = true;
// Filter out all the shortest response invokers
for (int i = 0; i < length; i++) {
Invoker invoker = invokers.get(i);
RpcStatus rpcStatus = RpcStatus.getStatus(invoker.getUrl(), invocation.getMethodName());
// Calculate the estimated response time from the product of active connections and succeeded average elapsed time.
long succeededAverageElapsed = rpcStatus.getSucceededAverageElapsed();
int active = rpcStatus.getActive() + 1;
long estimateResponse = succeededAverageElapsed * active;
int afterWarmup = getWeight(invoker, invocation);
weights[i] = afterWarmup;
// Same as LeastActiveLoadBalance
if (estimateResponse < shortestResponse) {
shortestResponse = estimateResponse;
shortestCount = 1;
shortestIndexes[0] = i;
totalWeight = afterWarmup;
firstWeight = afterWarmup;
sameWeight = true;
} else if (estimateResponse == shortestResponse) {
shortestIndexes[shortestCount++] = i;
totalWeight += afterWarmup;
if (sameWeight && i > 0
&& afterWarmup != firstWeight) {
sameWeight = false;
}
}
}
if (shortestCount == 1) {
return invokers.get(shortestIndexes[0]);
}
if (!sameWeight && totalWeight > 0) {
int offsetWeight = ThreadLocalRandom.current().nextInt(totalWeight);
for (int i = 0; i < shortestCount; i++) {
int shortestIndex = shortestIndexes[i];
offsetWeight -= weights[shortestIndex];
if (offsetWeight < 0) {
return invokers.get(shortestIndex);
}
}
}
return invokers.get(shortestIndexes[ThreadLocalRandom.current().nextInt(shortestCount)]);
}
}