001    /**
002     * Licensed to the Apache Software Foundation (ASF) under one
003     * or more contributor license agreements.  See the NOTICE file
004     * distributed with this work for additional information
005     * regarding copyright ownership.  The ASF licenses this file
006     * to you under the Apache License, Version 2.0 (the
007     * "License"); you may not use this file except in compliance
008     * with the License.  You may obtain a copy of the License at
009     *
010     *     http://www.apache.org/licenses/LICENSE-2.0
011     *
012     * Unless required by applicable law or agreed to in writing, software
013     * distributed under the License is distributed on an "AS IS" BASIS,
014     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015     * See the License for the specific language governing permissions and
016     * limitations under the License.
017     */
018    package org.apache.hadoop.hdfs.server.datanode;
019    
020    /**
021     * The caching strategy we should use for an HDFS read or write operation.
022     */
023    public class CachingStrategy {
024      private Boolean dropBehind; // null = use server defaults
025      private Long readahead; // null = use server defaults
026      
027      public static CachingStrategy newDefaultStrategy() {
028        return new CachingStrategy(null, null);
029      }
030    
031      public static CachingStrategy newDropBehind() {
032        return new CachingStrategy(true, null);
033      }
034    
035      public CachingStrategy duplicate() {
036        return new CachingStrategy(this.dropBehind, this.readahead);
037      }
038    
039      public CachingStrategy(Boolean dropBehind, Long readahead) {
040        this.dropBehind = dropBehind;
041        this.readahead = readahead;
042      }
043    
044      public Boolean getDropBehind() {
045        return dropBehind;
046      }
047      
048      public void setDropBehind(Boolean dropBehind) {
049        this.dropBehind = dropBehind;
050      }
051      
052      public Long getReadahead() {
053        return readahead;
054      }
055    
056      public void setReadahead(Long readahead) {
057        this.readahead = readahead;
058      }
059    
060      public String toString() {
061        return "CachingStrategy(dropBehind=" + dropBehind +
062            ", readahead=" + readahead + ")";
063      }
064    }