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.replication;
019
020import java.io.IOException;
021import java.util.ArrayList;
022import java.util.Collections;
023import java.util.List;
024import java.util.UUID;
025import org.apache.hadoop.hbase.Abortable;
026import org.apache.hadoop.hbase.ServerName;
027import org.apache.hadoop.hbase.util.EnvironmentEdgeManager;
028import org.apache.hadoop.hbase.zookeeper.ZKClusterId;
029import org.apache.hadoop.hbase.zookeeper.ZKListener;
030import org.apache.hadoop.hbase.zookeeper.ZKUtil;
031import org.apache.hadoop.hbase.zookeeper.ZKWatcher;
032import org.apache.yetus.audience.InterfaceAudience;
033import org.apache.zookeeper.KeeperException;
034import org.apache.zookeeper.KeeperException.AuthFailedException;
035import org.apache.zookeeper.KeeperException.ConnectionLossException;
036import org.apache.zookeeper.KeeperException.SessionExpiredException;
037import org.slf4j.Logger;
038import org.slf4j.LoggerFactory;
039
040/**
041 * A {@link BaseReplicationEndpoint} for replication endpoints whose target cluster is an HBase
042 * cluster.
043 */
044@InterfaceAudience.Private
045public abstract class HBaseReplicationEndpoint extends BaseReplicationEndpoint
046  implements Abortable {
047
048  private static final Logger LOG = LoggerFactory.getLogger(HBaseReplicationEndpoint.class);
049
050  private ZKWatcher zkw = null;
051
052  private List<ServerName> regionServers = new ArrayList<>(0);
053  private long lastRegionServerUpdate;
054
055  protected synchronized void disconnect() {
056    if (zkw != null) {
057      zkw.close();
058    }
059  }
060
061  /**
062   * A private method used to re-establish a zookeeper session with a peer cluster. n
063   */
064  protected void reconnect(KeeperException ke) {
065    if (
066      ke instanceof ConnectionLossException || ke instanceof SessionExpiredException
067        || ke instanceof AuthFailedException
068    ) {
069      String clusterKey = ctx.getPeerConfig().getClusterKey();
070      LOG.warn("Lost the ZooKeeper connection for peer " + clusterKey, ke);
071      try {
072        reloadZkWatcher();
073      } catch (IOException io) {
074        LOG.warn("Creation of ZookeeperWatcher failed for peer " + clusterKey, io);
075      }
076    }
077  }
078
079  @Override
080  public void start() {
081    startAsync();
082  }
083
084  @Override
085  public void stop() {
086    stopAsync();
087  }
088
089  @Override
090  protected void doStart() {
091    try {
092      reloadZkWatcher();
093      notifyStarted();
094    } catch (IOException e) {
095      notifyFailed(e);
096    }
097  }
098
099  @Override
100  protected void doStop() {
101    disconnect();
102    notifyStopped();
103  }
104
105  @Override
106  // Synchronize peer cluster connection attempts to avoid races and rate
107  // limit connections when multiple replication sources try to connect to
108  // the peer cluster. If the peer cluster is down we can get out of control
109  // over time.
110  public synchronized UUID getPeerUUID() {
111    UUID peerUUID = null;
112    try {
113      peerUUID = ZKClusterId.getUUIDForCluster(zkw);
114    } catch (KeeperException ke) {
115      reconnect(ke);
116    }
117    return peerUUID;
118  }
119
120  /**
121   * Get the ZK connection to this peer
122   * @return zk connection
123   */
124  protected synchronized ZKWatcher getZkw() {
125    return zkw;
126  }
127
128  /**
129   * Closes the current ZKW (if not null) and creates a new one
130   * @throws IOException If anything goes wrong connecting
131   */
132  synchronized void reloadZkWatcher() throws IOException {
133    if (zkw != null) zkw.close();
134    zkw = new ZKWatcher(ctx.getConfiguration(), "connection to cluster: " + ctx.getPeerId(), this);
135    getZkw().registerListener(new PeerRegionServerListener(this));
136  }
137
138  @Override
139  public void abort(String why, Throwable e) {
140    LOG.error("The HBaseReplicationEndpoint corresponding to peer " + ctx.getPeerId()
141      + " was aborted for the following reason(s):" + why, e);
142  }
143
144  @Override
145  public boolean isAborted() {
146    // Currently this is never "Aborted", we just log when the abort method is called.
147    return false;
148  }
149
150  /**
151   * Get the list of all the region servers from the specified peer
152   * @param zkw zk connection to use
153   * @return list of region server addresses or an empty list if the slave is unavailable
154   */
155  protected static List<ServerName> fetchSlavesAddresses(ZKWatcher zkw) throws KeeperException {
156    List<String> children =
157      ZKUtil.listChildrenAndWatchForNewChildren(zkw, zkw.getZNodePaths().rsZNode);
158    if (children == null) {
159      return Collections.emptyList();
160    }
161    List<ServerName> addresses = new ArrayList<>(children.size());
162    for (String child : children) {
163      addresses.add(ServerName.parseServerName(child));
164    }
165    return addresses;
166  }
167
168  /**
169   * Get a list of all the addresses of all the available region servers for this peer cluster, or
170   * an empty list if no region servers available at peer cluster.
171   * @return list of addresses
172   */
173  // Synchronize peer cluster connection attempts to avoid races and rate
174  // limit connections when multiple replication sources try to connect to
175  // the peer cluster. If the peer cluster is down we can get out of control
176  // over time.
177  public synchronized List<ServerName> getRegionServers() {
178    try {
179      setRegionServers(fetchSlavesAddresses(this.getZkw()));
180    } catch (KeeperException ke) {
181      if (LOG.isDebugEnabled()) {
182        LOG.debug("Fetch slaves addresses failed", ke);
183      }
184      reconnect(ke);
185    }
186    return regionServers;
187  }
188
189  /**
190   * Set the list of region servers for that peer
191   * @param regionServers list of addresses for the region servers
192   */
193  public synchronized void setRegionServers(List<ServerName> regionServers) {
194    this.regionServers = regionServers;
195    lastRegionServerUpdate = EnvironmentEdgeManager.currentTime();
196  }
197
198  /**
199   * Get the timestamp at which the last change occurred to the list of region servers to replicate
200   * to.
201   * @return The last time the list of peer region servers changed.
202   */
203  public long getLastRegionServerUpdate() {
204    return lastRegionServerUpdate;
205  }
206
207  /**
208   * Tracks changes to the list of region servers in a peer's cluster.
209   */
210  public static class PeerRegionServerListener extends ZKListener {
211
212    private final HBaseReplicationEndpoint replicationEndpoint;
213    private final String regionServerListNode;
214
215    public PeerRegionServerListener(HBaseReplicationEndpoint replicationPeer) {
216      super(replicationPeer.getZkw());
217      this.replicationEndpoint = replicationPeer;
218      this.regionServerListNode = replicationEndpoint.getZkw().getZNodePaths().rsZNode;
219    }
220
221    @Override
222    public synchronized void nodeChildrenChanged(String path) {
223      if (path.equals(regionServerListNode)) {
224        try {
225          LOG.info("Detected change to peer region servers, fetching updated list");
226          replicationEndpoint.setRegionServers(fetchSlavesAddresses(replicationEndpoint.getZkw()));
227        } catch (KeeperException e) {
228          LOG.error("Error reading slave addresses", e);
229        }
230      }
231    }
232  }
233}