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.client;
019
020import java.io.Closeable;
021import java.io.IOException;
022import java.util.HashSet;
023import java.util.Set;
024import java.util.concurrent.ExecutionException;
025import java.util.concurrent.ExecutorService;
026import java.util.concurrent.Executors;
027import java.util.concurrent.TimeUnit;
028import org.apache.hadoop.conf.Configuration;
029import org.apache.hadoop.hbase.ServerName;
030import org.apache.hadoop.hbase.util.EnvironmentEdgeManager;
031import org.apache.yetus.audience.InterfaceAudience;
032import org.slf4j.Logger;
033import org.slf4j.LoggerFactory;
034import org.apache.hbase.thirdparty.com.google.common.base.Preconditions;
035import org.apache.hbase.thirdparty.com.google.common.util.concurrent.ThreadFactoryBuilder;
036
037import org.apache.hadoop.hbase.shaded.protobuf.generated.MasterProtos.ClientMetaService;
038
039/**
040 * Thread safe utility that keeps master end points used by {@link MasterRegistry} up to date. This
041 * uses the RPC {@link ClientMetaService#getMasters} to fetch the latest list of registered masters.
042 * By default the refresh happens periodically (configured via
043 * {@link #PERIODIC_REFRESH_INTERVAL_SECS}). The refresh can also be triggered on demand via
044 * {@link #refreshNow()}. To prevent a flood of on-demand refreshes we expect that any attempts two
045 * should be spaced at least {@link #MIN_SECS_BETWEEN_REFRESHES} seconds apart.
046 */
047@InterfaceAudience.Private
048public class MasterAddressRefresher implements Closeable {
049  private static final Logger LOG = LoggerFactory.getLogger(MasterAddressRefresher.class);
050  public static final String PERIODIC_REFRESH_INTERVAL_SECS =
051      "hbase.client.master_registry.refresh_interval_secs";
052  private static final int PERIODIC_REFRESH_INTERVAL_SECS_DEFAULT = 300;
053  public static final String MIN_SECS_BETWEEN_REFRESHES =
054      "hbase.client.master_registry.min_secs_between_refreshes";
055  private static final int MIN_SECS_BETWEEN_REFRESHES_DEFAULT = 60;
056
057  private final ExecutorService pool;
058  private final MasterRegistry registry;
059  private final long periodicRefreshMs;
060  private final long timeBetweenRefreshesMs;
061  private final Object refreshMasters = new Object();
062
063  @Override
064  public void close() {
065    pool.shutdownNow();
066  }
067
068  /**
069   * Thread that refreshes the master end points until it is interrupted via {@link #close()}.
070   * Multiple callers attempting to refresh at the same time synchronize on {@link #refreshMasters}.
071   */
072  private class RefreshThread implements Runnable {
073    @Override
074    public void run() {
075      long lastRpcTs = 0;
076      while (!Thread.interrupted()) {
077        try {
078          // Spurious wake ups are okay, worst case we make an extra RPC call to refresh. We won't
079          // have duplicate refreshes because once the thread is past the wait(), notify()s are
080          // ignored until the thread is back to the waiting state.
081          synchronized (refreshMasters) {
082            refreshMasters.wait(periodicRefreshMs);
083          }
084          long currentTs = EnvironmentEdgeManager.currentTime();
085          if (lastRpcTs != 0 && currentTs - lastRpcTs <= timeBetweenRefreshesMs) {
086            continue;
087          }
088          lastRpcTs = currentTs;
089          LOG.debug("Attempting to refresh master address end points.");
090          Set<ServerName> newMasters = new HashSet<>(registry.getMasters().get());
091          registry.populateMasterStubs(newMasters);
092          LOG.debug("Finished refreshing master end points. {}", newMasters);
093        } catch (InterruptedException e) {
094          LOG.debug("Interrupted during wait, aborting refresh-masters-thread.", e);
095          break;
096        } catch (ExecutionException | IOException e) {
097          LOG.debug("Error populating latest list of masters.", e);
098        }
099      }
100      LOG.info("Master end point refresher loop exited.");
101    }
102  }
103
104  MasterAddressRefresher(Configuration conf, MasterRegistry registry) {
105    pool = Executors.newSingleThreadExecutor(new ThreadFactoryBuilder()
106        .setNameFormat("master-registry-refresh-end-points").setDaemon(true).build());
107    periodicRefreshMs = TimeUnit.SECONDS.toMillis(conf.getLong(PERIODIC_REFRESH_INTERVAL_SECS,
108        PERIODIC_REFRESH_INTERVAL_SECS_DEFAULT));
109    timeBetweenRefreshesMs = TimeUnit.SECONDS.toMillis(conf.getLong(MIN_SECS_BETWEEN_REFRESHES,
110        MIN_SECS_BETWEEN_REFRESHES_DEFAULT));
111    Preconditions.checkArgument(periodicRefreshMs > 0);
112    Preconditions.checkArgument(timeBetweenRefreshesMs < periodicRefreshMs);
113    this.registry = registry;
114    pool.submit(new RefreshThread());
115  }
116
117  /**
118   * Notifies the refresher thread to refresh the configuration. This does not guarantee a refresh.
119   * See class comment for details.
120   */
121  void refreshNow() {
122    synchronized (refreshMasters) {
123      refreshMasters.notify();
124    }
125  }
126}