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.memory.buffer; 018 019 import java.util.Iterator; 020 import java.util.LinkedList; 021 022 /** 023 * A {@link MessageBuffer} which evicts messages in arrival order so the oldest 024 * messages are removed first. 025 * 026 * @version $Revision: 1.1 $ 027 */ 028 public class OrderBasedMessageBuffer implements MessageBuffer { 029 030 private int limit = 100 * 64 * 1024; 031 private LinkedList<MessageQueue> list = new LinkedList<MessageQueue>(); 032 private int size; 033 private Object lock = new Object(); 034 035 public OrderBasedMessageBuffer() { 036 } 037 038 public OrderBasedMessageBuffer(int limit) { 039 this.limit = limit; 040 } 041 042 public int getSize() { 043 synchronized (lock) { 044 return size; 045 } 046 } 047 048 /** 049 * Creates a new message queue instance 050 */ 051 public MessageQueue createMessageQueue() { 052 return new MessageQueue(this); 053 } 054 055 /** 056 * After a message queue has changed we may need to perform some evictions 057 * 058 * @param delta 059 * @param queueSize 060 */ 061 public void onSizeChanged(MessageQueue queue, int delta, int queueSize) { 062 synchronized (lock) { 063 list.addLast(queue); 064 size += delta; 065 while (size > limit) { 066 MessageQueue biggest = list.removeFirst(); 067 size -= biggest.evictMessage(); 068 } 069 } 070 } 071 072 public void clear() { 073 synchronized (lock) { 074 for (Iterator<MessageQueue> iter = list.iterator(); iter.hasNext();) { 075 MessageQueue queue = iter.next(); 076 queue.clear(); 077 } 078 size = 0; 079 } 080 } 081 082 }