001/**
002 *
003 * Licensed to the Apache Software Foundation (ASF) under one
004 * or more contributor license agreements.  See the NOTICE file
005 * distributed with this work for additional information
006 * regarding copyright ownership.  The ASF licenses this file
007 * to you under the Apache License, Version 2.0 (the
008 * "License"); you may not use this file except in compliance
009 * with the License.  You may obtain a copy of the License at
010 *
011 *     http://www.apache.org/licenses/LICENSE-2.0
012 *
013 * Unless required by applicable law or agreed to in writing, software
014 * distributed under the License is distributed on an "AS IS" BASIS,
015 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
016 * See the License for the specific language governing permissions and
017 * limitations under the License.
018 */
019
020package org.apache.hadoop.hbase.mob;
021
022import java.io.Closeable;
023import java.io.IOException;
024
025import org.apache.hadoop.hbase.Cell;
026import org.apache.hadoop.hbase.regionserver.StoreFileScanner;
027import org.apache.yetus.audience.InterfaceAudience;
028
029/**
030 * The MobCell will maintain a {@link Cell} and a {@link StoreFileScanner} inside. Now, the mob cell
031 * is backend by NIO ByteBuffers which are allocated from ByteBuffAllocator, so we cannot just read
032 * the cell and close the MOB file scanner because the MOB file scanner closing will deallocate the
033 * NIO ByteBuffers, which resulting memory leak.
034 * <p>
035 * Actually, the right solution is: <br>
036 * 1. Read the normal cell; <br>
037 * 2. Parse the value of normal cell and get MOB fileName,offset,length; <br>
038 * 3. Open scanner to read the mob value; <br>
039 * 4. Construct the response cell whose key is from the normal cell and value is from the mob cell.
040 * <br>
041 * 5. Ship the response cell to HBase client. <br>
042 * 6. Release both normal cell's block and mob cell's block. <br>
043 * <p>
044 * For mob cell, the block releasing just means closing the the mob scanner, so here we need to keep
045 * the {@link StoreFileScanner} inside and close only when we're ensure that the MobCell has been
046 * shipped to RPC client.
047 */
048@InterfaceAudience.Private
049public class MobCell implements Closeable {
050
051  private final Cell cell;
052  private final StoreFileScanner sfScanner;
053
054  public MobCell(Cell cell) {
055    this.cell = cell;
056    this.sfScanner = null;
057  }
058
059  public MobCell(Cell cell, StoreFileScanner sfScanner) {
060    this.cell = cell;
061    this.sfScanner = sfScanner;
062  }
063
064  public Cell getCell() {
065    return cell;
066  }
067
068  @Override
069  public void close() throws IOException {
070    if (this.sfScanner != null) {
071      this.sfScanner.close();
072    }
073  }
074}