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.activemq.memory.buffer; 018 019import java.util.ArrayList; 020import java.util.Iterator; 021import java.util.List; 022 023/** 024 * A {@link MessageBuffer} which evicts from the largest buffers first. 025 * 026 * 027 */ 028public class SizeBasedMessageBuffer implements MessageBuffer { 029 030 private int limit = 100 * 64 * 1024; 031 private List<MessageQueue> bubbleList = new ArrayList<MessageQueue>(); 032 private int size; 033 private Object lock = new Object(); 034 035 public SizeBasedMessageBuffer() { 036 } 037 038 public SizeBasedMessageBuffer(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 MessageQueue queue = new MessageQueue(this); 053 synchronized (lock) { 054 queue.setPosition(bubbleList.size()); 055 bubbleList.add(queue); 056 } 057 return queue; 058 } 059 060 /** 061 * After a message queue has changed we may need to perform some evictions 062 * 063 * @param delta 064 * @param queueSize 065 */ 066 public void onSizeChanged(MessageQueue queue, int delta, int queueSize) { 067 synchronized (lock) { 068 bubbleUp(queue, queueSize); 069 070 size += delta; 071 while (size > limit) { 072 MessageQueue biggest = bubbleList.get(0); 073 size -= biggest.evictMessage(); 074 075 bubbleDown(biggest, 0); 076 } 077 } 078 } 079 080 public void clear() { 081 synchronized (lock) { 082 for (Iterator<MessageQueue> iter = bubbleList.iterator(); iter.hasNext();) { 083 MessageQueue queue = iter.next(); 084 queue.clear(); 085 } 086 size = 0; 087 } 088 } 089 090 protected void bubbleUp(MessageQueue queue, int queueSize) { 091 // lets bubble up to head of queueif we need to 092 int position = queue.getPosition(); 093 while (--position >= 0) { 094 MessageQueue pivot = bubbleList.get(position); 095 if (pivot.getSize() < queueSize) { 096 swap(position, pivot, position + 1, queue); 097 } else { 098 break; 099 } 100 } 101 } 102 103 protected void bubbleDown(MessageQueue biggest, int position) { 104 int queueSize = biggest.getSize(); 105 int end = bubbleList.size(); 106 for (int second = position + 1; second < end; second++) { 107 MessageQueue pivot = bubbleList.get(second); 108 if (pivot.getSize() > queueSize) { 109 swap(position, biggest, second, pivot); 110 } else { 111 break; 112 } 113 position = second; 114 } 115 } 116 117 protected void swap(int firstPosition, MessageQueue first, int secondPosition, MessageQueue second) { 118 bubbleList.set(firstPosition, second); 119 bubbleList.set(secondPosition, first); 120 first.setPosition(secondPosition); 121 second.setPosition(firstPosition); 122 } 123}