001/**
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.camel.processor.loadbalancer;
018
019import java.util.List;
020import java.util.Random;
021
022import org.apache.camel.Exchange;
023import org.apache.camel.Processor;
024
025public class WeightedRandomLoadBalancer extends WeightedLoadBalancer {
026    private final Random rnd = new Random();
027    private final int distributionRatioSum;
028    private int runtimeRatioSum;
029    
030    public WeightedRandomLoadBalancer(List<Integer> distributionRatioList) {
031        super(distributionRatioList);
032        int sum = 0;
033        for (Integer distributionRatio : distributionRatioList) {
034            sum += distributionRatio;
035        }
036        distributionRatioSum = sum;
037        runtimeRatioSum = distributionRatioSum;
038    }
039    
040    @Override
041    protected Processor chooseProcessor(List<Processor> processors, Exchange exchange) {        
042        int selectedProcessorIndex = selectProcessIndex();
043        return processors.get(selectedProcessorIndex);
044    }
045    
046    public int selectProcessIndex() {
047        if (runtimeRatioSum == 0) { // every processor is exhausted, reload for a new distribution round
048            for (DistributionRatio distributionRatio : getRuntimeRatios()) {
049                int weight = distributionRatio.getDistributionWeight();
050                distributionRatio.setRuntimeWeight(weight);
051            }
052            runtimeRatioSum = distributionRatioSum;
053        }
054
055        DistributionRatio selected = null;
056        int randomWeight = rnd.nextInt(runtimeRatioSum);
057        int choiceWeight = 0;
058        for (DistributionRatio distributionRatio : getRuntimeRatios()) {
059            choiceWeight += distributionRatio.getRuntimeWeight();
060            if (randomWeight < choiceWeight) {
061                selected = distributionRatio;
062                break;
063            }
064        }
065        
066        selected.setRuntimeWeight(selected.getRuntimeWeight() - 1);
067        runtimeRatioSum--;
068
069        return selected.getProcessorPosition();
070    }
071}