hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/RegionSplitPolicy.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 package org.apache.hadoop.hbase.regionserver;
  19
  20 import java.io.IOException;
  21 import java.util.List;
  22 import java.util.Optional;
  23
  24 import org.apache.hadoop.conf.Configuration;
  25 import org.apache.hadoop.conf.Configured;
  26 import org.apache.hadoop.hbase.HBaseInterfaceAudience;
  27 import org.apache.hadoop.hbase.HConstants;
  28 import org.apache.hadoop.hbase.client.TableDescriptor;
  29 import org.apache.hadoop.util.ReflectionUtils;
  30 import org.apache.yetus.audience.InterfaceAudience;
  31 import org.apache.hbase.thirdparty.com.google.common.base.Preconditions;
  32
  33
  34 /**
  35  * A split policy determines when a Region should be split.
  36  *
  37  * @see SteppingSplitPolicy Default split policy since 2.0.0
  38  * @see IncreasingToUpperBoundRegionSplitPolicy Default split policy since
  39  *      0.94.0
  40  * @see ConstantSizeRegionSplitPolicy Default split policy before 0.94.0
  41  */
  42 @InterfaceAudience.LimitedPrivate(HBaseInterfaceAudience.CONFIG)
  43 public abstract class RegionSplitPolicy extends Configured {
  44   private static final Class<? extends RegionSplitPolicy>
  45     DEFAULT_SPLIT_POLICY_CLASS = SteppingSplitPolicy.class;
  46
  47   /**
  48    * The region configured for this split policy.
  49    * As of hbase-2.0.0, RegionSplitPolicy can be instantiated on the Master-side so the
  50    * Phoenix local-indexer can block default hbase behavior. This is an exotic usage. Should not
  51    * trouble any other users of RegionSplitPolicy.
  52    */
  53   protected HRegion region;
  54
  55   /**
  56    * Upon construction, this method will be called with the region
  57    * to be governed. It will be called once and only once.
  58    */
  59   protected void configureForRegion(HRegion region) {
  60     Preconditions.checkState(
  61         this.region == null,
  62         "Policy already configured for region {}",
  63         this.region);
  64
  65     this.region = region;
  66   }
  67
  68   /**
  69    * @return true if the specified region should be split.
  70    */
  71   protected abstract boolean shouldSplit();
  72
  73   /**
  74    * @return the key at which the region should be split, or null
  75    * if it cannot be split. This will only be called if shouldSplit
  76    * previously returned true.
  77    */
  78   protected byte[] getSplitPoint() {
  79     byte[] explicitSplitPoint = this.region.getExplicitSplitPoint();
  80     if (explicitSplitPoint != null) {
  81       return explicitSplitPoint;
  82     }
  83     List<HStore> stores = region.getStores();
  84
  85     byte[] splitPointFromLargestStore = null;
  86     long largestStoreSize = 0;
  87     for (HStore s : stores) {
  88       Optional<byte[]> splitPoint = s.getSplitPoint();
  89       // Store also returns null if it has references as way of indicating it is not splittable
  90       long storeSize = s.getSize();
  91       if (splitPoint.isPresent() && largestStoreSize < storeSize) {
  92         splitPointFromLargestStore = splitPoint.get();
  93         largestStoreSize = storeSize;
  94       }
  95     }
  96
  97     return splitPointFromLargestStore;
  98   }
  99
 100   /**
 101    * Create the RegionSplitPolicy configured for the given table.
 102    * @param region
 103    * @param conf
 104    * @return a RegionSplitPolicy
 105    * @throws IOException
 106    */
 107   public static RegionSplitPolicy create(HRegion region,
 108       Configuration conf) throws IOException {
 109     Preconditions.checkNotNull(region, "Region should not be null.");
 110     Class<? extends RegionSplitPolicy> clazz = getSplitPolicyClass(
 111         region.getTableDescriptor(), conf);
 112     RegionSplitPolicy policy = ReflectionUtils.newInstance(clazz, conf);
 113     policy.configureForRegion(region);
 114     return policy;
 115   }
 116
 117   public static Class<? extends RegionSplitPolicy> getSplitPolicyClass(
 118       TableDescriptor htd, Configuration conf) throws IOException {
 119     String className = htd.getRegionSplitPolicyClassName();
 120     if (className == null) {
 121       className = conf.get(HConstants.HBASE_REGION_SPLIT_POLICY_KEY,
 122           DEFAULT_SPLIT_POLICY_CLASS.getName());
 123     }
 124
 125     try {
 126       Class<? extends RegionSplitPolicy> clazz =
 127         Class.forName(className).asSubclass(RegionSplitPolicy.class);
 128       return clazz;
 129     } catch (Exception  e) {
 130       throw new IOException(
 131           "Unable to load configured region split policy '" +
 132           className + "' for table '" + htd.getTableName() + "'",
 133           e);
 134     }
 135   }
 136
 137   /**
 138    * In {@link HRegionFileSystem#splitStoreFile(org.apache.hadoop.hbase.client.RegionInfo, String,
 139    * HStoreFile, byte[], boolean, RegionSplitPolicy)} we are not creating the split reference
 140    * if split row does not lie inside the StoreFile range. But in some use cases we may need to
 141    * create the split reference even when the split row does not lie inside the StoreFile range.
 142    * This method can be used to decide, whether to skip the the StoreFile range check or not.
 143    *
 144    * <p>This method is not for general use. It is a mechanism put in place by Phoenix
 145    * local indexing to defeat standard hbase behaviors. Phoenix local indices are very likely
 146    * the only folks who would make use of this method. On the Master-side, we will instantiate
 147    * a RegionSplitPolicy instance and run this method ONLY... none of the others make sense
 148    * on the Master-side.</p>
 149    *
 150    * TODO: Shutdown this phoenix specialization or do it via some other means.
 151    * @return whether to skip the StoreFile range check or not
 152    */
 153   protected boolean skipStoreFileRangeCheck(String familyName) {
 154     return false;
 155   }
 156 }