| /** |
| * 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.camel.processor.loadbalancer; |
| |
| import java.util.HashMap; |
| import java.util.Iterator; |
| import java.util.List; |
| import java.util.Map; |
| |
| import org.apache.camel.Exchange; |
| import org.apache.camel.Expression; |
| import org.apache.camel.Processor; |
| |
| /** |
| * Implements a sticky load balancer using an {@link Expression} to calculate |
| * a correlation key to perform the sticky load balancing; rather like jsessionid in the web |
| * or JMSXGroupID in JMS. |
| * |
| * @version |
| */ |
| public class StickyLoadBalancer extends QueueLoadBalancer { |
| private Expression correlationExpression; |
| private QueueLoadBalancer loadBalancer; |
| private int numberOfHashGroups = 64 * 1024; |
| private final Map<Object, Processor> stickyMap = new HashMap<Object, Processor>(); |
| |
| public StickyLoadBalancer(Expression correlationExpression) { |
| this(correlationExpression, new RoundRobinLoadBalancer()); |
| } |
| |
| public StickyLoadBalancer(Expression correlationExpression, QueueLoadBalancer loadBalancer) { |
| super(); |
| this.correlationExpression = correlationExpression; |
| this.loadBalancer = loadBalancer; |
| } |
| |
| public Expression getCorrelationExpression() { |
| return correlationExpression; |
| } |
| |
| protected synchronized Processor chooseProcessor(List<Processor> processors, Exchange exchange) { |
| Object value = correlationExpression.evaluate(exchange, Object.class); |
| Object key = getStickyKey(value); |
| |
| Processor processor; |
| synchronized (stickyMap) { |
| processor = stickyMap.get(key); |
| if (processor == null) { |
| processor = loadBalancer.chooseProcessor(processors, exchange); |
| stickyMap.put(key, processor); |
| } |
| } |
| return processor; |
| } |
| |
| @Override |
| public void removeProcessor(Processor processor) { |
| synchronized (stickyMap) { |
| Iterator<Map.Entry<Object, Processor>> iter = stickyMap.entrySet().iterator(); |
| while (iter.hasNext()) { |
| Map.Entry<Object, Processor> entry = iter.next(); |
| if (processor.equals(entry.getValue())) { |
| iter.remove(); |
| } |
| } |
| } |
| super.removeProcessor(processor); |
| } |
| |
| |
| // Properties |
| //------------------------------------------------------------------------- |
| public int getNumberOfHashGroups() { |
| return numberOfHashGroups; |
| } |
| |
| public void setNumberOfHashGroups(int numberOfHashGroups) { |
| this.numberOfHashGroups = numberOfHashGroups; |
| } |
| |
| // Implementation methods |
| //------------------------------------------------------------------------- |
| |
| /** |
| * A strategy to create the key for the sticky load balancing map. |
| * The default implementation uses the hash code of the value |
| * then modulos by the numberOfHashGroups to avoid the sticky map getting too big |
| * |
| * @param value the correlation value |
| * @return the key to be used in the sticky map |
| */ |
| protected Object getStickyKey(Object value) { |
| int hashCode = 37; |
| if (value != null) { |
| hashCode = value.hashCode(); |
| } |
| if (numberOfHashGroups > 0) { |
| hashCode = hashCode % numberOfHashGroups; |
| } |
| return hashCode; |
| } |
| |
| public String toString() { |
| return "StickyLoadBalancer"; |
| } |
| |
| } |