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 */
018package org.apache.hadoop.hbase.regionserver;
019
020import org.apache.hadoop.conf.Configuration;
021import org.apache.hadoop.hbase.conf.ConfigurationManager;
022import org.apache.hadoop.hbase.conf.PropagatingConfigurationObserver;
023import org.apache.hadoop.hbase.io.hfile.PrefetchExecutor;
024import org.apache.yetus.audience.InterfaceAudience;
025import org.slf4j.Logger;
026import org.slf4j.LoggerFactory;
027
028/**
029 * Class to submit requests for PrefetchExecutor depending on configuration change
030 */
031@InterfaceAudience.Private
032public final class PrefetchExecutorNotifier implements PropagatingConfigurationObserver {
033  private static final Logger LOG = LoggerFactory.getLogger(PrefetchExecutorNotifier.class);
034
035  /** Wait time in miliseconds before executing prefetch */
036  public static final String PREFETCH_DELAY = "hbase.hfile.prefetch.delay";
037  private final Configuration conf;
038
039  // only for test
040  public PrefetchExecutorNotifier(Configuration conf) {
041    this.conf = conf;
042  }
043
044  /**
045   * {@inheritDoc}
046   */
047  @Override
048  public void onConfigurationChange(Configuration newConf) {
049    // Update prefetch delay in the prefetch executor class
050    // interrupt and restart threads which have not started executing
051    PrefetchExecutor.loadConfiguration(conf);
052    LOG.info("Config hbase.hfile.prefetch.delay is changed to {}",
053      conf.getInt(PREFETCH_DELAY, 1000));
054  }
055
056  /**
057   * {@inheritDoc}
058   */
059  @Override
060  public void registerChildren(ConfigurationManager manager) {
061    // No children to register.
062  }
063
064  /**
065   * {@inheritDoc}
066   */
067  @Override
068  public void deregisterChildren(ConfigurationManager manager) {
069    // No children to register
070  }
071
072  public int getPrefetchDelay() {
073    return PrefetchExecutor.getPrefetchDelay();
074  }
075}