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.io.IOException; 020 import java.util.LinkedList; 021 022 import org.apache.activemq.broker.region.MessageReference; 023 024 /** 025 * A strategy for evicting messages from slow consumers. 026 * 027 * @version $Revision: 564057 $ 028 */ 029 public interface MessageEvictionStrategy { 030 031 /** 032 * Find the message reference in the given list with oldest messages at the front and newer messages at the end 033 * 034 * @return the message that has been evicted. 035 * @throws IOException if an exception occurs such as reading a message content (but should not ever happen 036 * as usually all the messages will be in RAM when this method is called). 037 */ 038 MessageReference[] evictMessages(LinkedList messages) throws IOException; 039 040 /** 041 * REturns the high water mark on which we will eagerly evict expired messages from RAM 042 */ 043 int getEvictExpiredMessagesHighWatermark(); 044 045 }