dubbo LeastActiveLoadBalance 代码
文件路径：/dubbo-cluster/src/main/java/org/apache/dubbo/rpc/cluster/loadbalance/LeastActiveLoadBalance.java
/*
* 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;
/**
* LeastActiveLoadBalance
* <p>
* Filter the number of invokers with the least number of active 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 LeastActiveLoadBalance extends AbstractLoadBalance {
public static final String NAME = "leastactive";
@Override
protected <T> Invoker<T> doSelect(List<Invoker<T>> invokers, URL url, Invocation invocation) {
/ Number of invokers
int length = invokers.size();
/ The least active value of all invokers
int leastActive = -1;
/ The number of invokers having the same least active value (leastActive)
int leastCount = 0;
/ The index of invokers having the same least active value (leastActive)
int[] leastIndexes = new int[length];
/ the weight of every invokers
int[] weights = new int[length];
/ The sum of the warmup weights of all the least active invokers
int totalWeight = 0;
/ The weight of the first least active invoker
int firstWeight = 0;
/ Every least active invoker has the same weight value?
boolean sameWeight = true;
/ Filter out all the least active invokers
for (int i = 0; i < length; i++) {
Invoker<T> invoker = invokers.get(i);
/ Get the active number of the invoker
int active = RpcStatus.getStatus(invoker.getUrl(), invocation.getMethodName()).getActive();
/ Get the weight of the invoker's configuration. The default value is 100.
int afterWarmup = getWeight(invoker, invocation);
/ save for later use
weights[i] = afterWarmup;
/ If it is the first invoker or the active number of the invoker is less than the current least active number
if (leastActive == -1 || active < leastActive) {
/ Reset the active number of the current invoker to the least active number
leastActive = active;
/ Reset the number of least active invokers
leastCount = 1;
/ Put the first least active invoker first in leastIndexes
leastIndexes[0] = i;
/ Reset totalWeight
totalWeight = afterWarmup;
/ Record the weight the first least active invoker
firstWeight = afterWarmup;
/ Each invoke has the same weight (only one invoker here)
sameWeight = true;
/ If current invoker's active value equals with leaseActive, then accumulating.
} else if (active == leastActive) {
/ Record the index of the least active invoker in leastIndexes order
leastIndexes[leastCount++] = i;
/ Accumulate the total weight of the least active invoker
totalWeight += afterWarmup;
/ If every invoker has the same weight?
if (sameWeight && afterWarmup != firstWeight) {
sameWeight = false;
}
}
}
/ Choose an invoker from all the least active invokers
if (leastCount == 1) {
/ If we got exactly one invoker having the least active value, return this invoker directly.
return invokers.get(leastIndexes[0]);
}
if (!sameWeight && totalWeight > 0) {
/ If (not every invoker has the same weight & at least one invoker's weight>0), select randomly based on
/ totalWeight.
int offsetWeight = ThreadLocalRandom.current().nextInt(totalWeight);
/ Return a invoker based on the random value.
for (int i = 0; i < leastCount; i++) {
int leastIndex = leastIndexes[i];
offsetWeight -= weights[leastIndex];
if (offsetWeight < 0) {
return invokers.get(leastIndex);
}
}
}
/ If all invokers have the same weight value or totalWeight=0, return evenly.
return invokers.get(leastIndexes[ThreadLocalRandom.current().nextInt(leastCount)]);
}
}