hbase-server/src/main/java/org/apache/hadoop/hbase/client/ClientSideRegionScanner.java

   1 /**
   2  * Licensed to the Apache Software Foundation (ASF) under one
   3  * or more contributor license agreements.  See the NOTICE file
   4  * distributed with this work for additional information
   5  * regarding copyright ownership.  The ASF licenses this file
   6  * to you under the Apache License, Version 2.0 (the
   7  * "License"); you may not use this file except in compliance
   8  * with the License.  You may obtain a copy of the License at
   9  *
  10  *     http://www.apache.org/licenses/LICENSE-2.0
  11  *
  12  * Unless required by applicable law or agreed to in writing, software
  13  * distributed under the License is distributed on an "AS IS" BASIS,
  14  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  15  * See the License for the specific language governing permissions and
  16  * limitations under the License.
  17  */
  18
  19 package org.apache.hadoop.hbase.client;
  20
  21 import java.io.IOException;
  22 import java.util.ArrayList;
  23 import java.util.List;
  24
  25 import org.apache.commons.logging.Log;
  26 import org.apache.commons.logging.LogFactory;
  27 import org.apache.hadoop.conf.Configuration;
  28 import org.apache.hadoop.fs.FileSystem;
  29 import org.apache.hadoop.fs.Path;
  30 import org.apache.hadoop.hbase.Cell;
  31 import org.apache.hadoop.hbase.CellUtil;
  32 import org.apache.hadoop.hbase.HRegionInfo;
  33 import org.apache.hadoop.hbase.classification.InterfaceAudience;
  34 import org.apache.hadoop.hbase.client.metrics.ScanMetrics;
  35 import org.apache.hadoop.hbase.regionserver.HRegion;
  36 import org.apache.hadoop.hbase.regionserver.RegionScanner;
  37
  38 /**
  39  * A client scanner for a region opened for read-only on the client side. Assumes region data
  40  * is not changing.
  41  */
  42 @InterfaceAudience.Private
  43 public class ClientSideRegionScanner extends AbstractClientScanner {
  44
  45   private static final Log LOG = LogFactory.getLog(ClientSideRegionScanner.class);
  46
  47   private HRegion region;
  48   RegionScanner scanner;
  49   List<Cell> values;
  50
  51   public ClientSideRegionScanner(Configuration conf, FileSystem fs,
  52       Path rootDir, TableDescriptor htd, HRegionInfo hri, Scan scan, ScanMetrics scanMetrics)
  53           throws IOException {
  54     // region is immutable, set isolation level
  55     scan.setIsolationLevel(IsolationLevel.READ_UNCOMMITTED);
  56
  57     // open region from the snapshot directory
  58     this.region = HRegion.openHRegion(conf, fs, rootDir, hri, htd, null, null, null);
  59
  60     // create an internal region scanner
  61     this.scanner = region.getScanner(scan);
  62     values = new ArrayList<>();
  63
  64     if (scanMetrics == null) {
  65       initScanMetrics(scan);
  66     } else {
  67       this.scanMetrics = scanMetrics;
  68     }
  69     region.startRegionOperation();
  70   }
  71
  72   @Override
  73   public Result next() throws IOException {
  74     values.clear();
  75     scanner.nextRaw(values);
  76     if (values.isEmpty()) {
  77       //we are done
  78       return null;
  79     }
  80
  81     Result result = Result.create(values);
  82     if (this.scanMetrics != null) {
  83       long resultSize = 0;
  84       for (Cell cell : values) {
  85         resultSize += CellUtil.estimatedSerializedSizeOf(cell);
  86       }
  87       this.scanMetrics.countOfBytesInResults.addAndGet(resultSize);
  88     }
  89
  90     return result;
  91   }
  92
  93   @Override
  94   public void close() {
  95     if (this.scanner != null) {
  96       try {
  97         this.scanner.close();
  98         this.scanner = null;
  99       } catch (IOException ex) {
 100         LOG.warn("Exception while closing scanner", ex);
 101       }
 102     }
 103     if (this.region != null) {
 104       try {
 105         this.region.closeRegionOperation();
 106         this.region.close(true);
 107         this.region = null;
 108       } catch (IOException ex) {
 109         LOG.warn("Exception while closing region", ex);
 110       }
 111     }
 112   }
 113
 114   @Override
 115   public boolean renewLease() {
 116     throw new UnsupportedOperationException();
 117   }
 118 }