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 */
019package org.apache.hadoop.hbase.wal;
020
021import static org.apache.hadoop.hbase.util.CollectionUtils.computeIfAbsent;
022
023import java.util.concurrent.ConcurrentHashMap;
024import java.util.concurrent.atomic.AtomicInteger;
025
026import org.apache.hadoop.conf.Configuration;
027import org.apache.yetus.audience.InterfaceAudience;
028import org.apache.hadoop.hbase.util.Bytes;
029import org.apache.hadoop.hbase.wal.RegionGroupingProvider.RegionGroupingStrategy;
030
031/**
032 * A WAL grouping strategy that limits the number of wal groups to
033 * "hbase.wal.regiongrouping.numgroups".
034 */
035@InterfaceAudience.Private
036public class BoundedGroupingStrategy implements RegionGroupingStrategy{
037
038  static final String NUM_REGION_GROUPS = "hbase.wal.regiongrouping.numgroups";
039  static final int DEFAULT_NUM_REGION_GROUPS = 2;
040
041  private ConcurrentHashMap<String, String> groupNameCache = new ConcurrentHashMap<>();
042  private AtomicInteger counter = new AtomicInteger(0);
043  private String[] groupNames;
044
045  @Override
046  public String group(byte[] identifier, byte[] namespace) {
047    String idStr = Bytes.toString(identifier);
048    return computeIfAbsent(groupNameCache, idStr,
049      () -> groupNames[getAndIncrAtomicInteger(counter, groupNames.length)]);
050  }
051
052  // Non-blocking incrementing & resetting of AtomicInteger.
053  private int getAndIncrAtomicInteger(AtomicInteger atomicInt, int reset) {
054    for (;;) {
055      int current = atomicInt.get();
056      int next = (current + 1);
057      if (next == reset) {
058        next = 0;
059      }
060      if (atomicInt.compareAndSet(current, next)) return current;
061    }
062  }
063
064  @Override
065  public void init(Configuration config, String providerId) {
066    int regionGroupNumber = config.getInt(NUM_REGION_GROUPS, DEFAULT_NUM_REGION_GROUPS);
067    groupNames = new String[regionGroupNumber];
068    for (int i = 0; i < regionGroupNumber; i++) {
069      groupNames[i] = providerId + GROUP_NAME_DELIMITER + "regiongroup-" + i;
070    }
071  }
072
073}