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.activemq.broker.region.policy; 018 019 import java.util.Iterator; 020 import java.util.List; 021 import org.apache.activemq.broker.region.MessageReference; 022 import org.apache.activemq.broker.region.Subscription; 023 import org.apache.activemq.filter.MessageEvaluationContext; 024 import org.apache.commons.logging.Log; 025 import org.apache.commons.logging.LogFactory; 026 027 /** 028 * Simple dispatch policy that sends a message to every subscription that 029 * matches the message. 030 * 031 * @org.apache.xbean.XBean 032 * @version $Revision$ 033 */ 034 public class RoundRobinDispatchPolicy implements DispatchPolicy { 035 static final Log LOG = LogFactory.getLog(RoundRobinDispatchPolicy.class); 036 037 /** 038 * @param node 039 * @param msgContext 040 * @param consumers 041 * @return true if dispatched 042 * @throws Exception 043 * @see org.apache.activemq.broker.region.policy.DispatchPolicy#dispatch(org.apache.activemq.broker.region.MessageReference, 044 * org.apache.activemq.filter.MessageEvaluationContext, java.util.List) 045 */ 046 public boolean dispatch(MessageReference node, 047 MessageEvaluationContext msgContext, List<Subscription> consumers) 048 throws Exception { 049 int count = 0; 050 051 Subscription firstMatchingConsumer = null; 052 synchronized (consumers) { 053 for (Iterator<Subscription> iter = consumers.iterator(); iter 054 .hasNext();) { 055 Subscription sub = iter.next(); 056 057 // Only dispatch to interested subscriptions 058 if (!sub.matches(node, msgContext)) { 059 continue; 060 } 061 062 if (firstMatchingConsumer == null) { 063 firstMatchingConsumer = sub; 064 } 065 066 sub.add(node); 067 count++; 068 } 069 070 if (firstMatchingConsumer != null) { 071 // Rotate the consumer list. 072 try { 073 consumers.remove(firstMatchingConsumer); 074 consumers.add(firstMatchingConsumer); 075 } catch (Throwable bestEffort) { 076 } 077 } 078 } 079 return count > 0; 080 } 081 }