content: /**
   * 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.activemq.broker.region.policy;
  
  import java.io.IOException;
  import java.util.LinkedList;
  
  import org.apache.activemq.broker.region.MessageReference;
  
  /**
   * A strategy for evicting messages from slow consumers.
   * 
   * 
   */
  public interface MessageEvictionStrategy {
  
      /**
       * Find the message reference in the given list with oldest messages at the front and newer messages at the end
       * 
       * @return the message that has been evicted.
       * @throws IOException if an exception occurs such as reading a message content (but should not ever happen
       * as usually all the messages will be in RAM when this method is called).
       */
      MessageReference[] evictMessages(LinkedList messages) throws IOException;
  
      /**
       * REturns the high water mark on which we will eagerly evict expired messages from RAM
       */
      int getEvictExpiredMessagesHighWatermark();
  
  }
  