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     */
017    package org.apache.camel.processor.loadbalancer;
018    
019    import java.util.List;
020    import java.util.Random;
021    
022    import org.apache.camel.Exchange;
023    import org.apache.camel.Processor;
024    
025    public 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    }