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1   /*
2    *
3    * Licensed to the Apache Software Foundation (ASF) under one
4    * or more contributor license agreements.  See the NOTICE file
5    * distributed with this work for additional information
6    * regarding copyright ownership.  The ASF licenses this file
7    * to you under the Apache License, Version 2.0 (the
8    * "License"); you may not use this file except in compliance
9    * with the License.  You may obtain a copy of the License at
10   *
11   *     http://www.apache.org/licenses/LICENSE-2.0
12   *
13   * Unless required by applicable law or agreed to in writing, software
14   * distributed under the License is distributed on an "AS IS" BASIS,
15   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
16   * See the License for the specific language governing permissions and
17   * limitations under the License.
18   */
19  package org.apache.hadoop.hbase.replication;
20  
21  import java.util.List;
22  
23  import org.apache.hadoop.hbase.classification.InterfaceAudience;
24  import org.apache.hadoop.conf.Configuration;
25  import org.apache.hadoop.hbase.Abortable;
26  import org.apache.hadoop.hbase.protobuf.ProtobufUtil;
27  import org.apache.hadoop.hbase.protobuf.generated.ZooKeeperProtos;
28  import org.apache.hadoop.hbase.zookeeper.ZKConfig;
29  import org.apache.hadoop.hbase.zookeeper.ZKUtil;
30  import org.apache.hadoop.hbase.zookeeper.ZooKeeperWatcher;
31  import org.apache.zookeeper.KeeperException;
32  
33  
34  /**
35   * This is a base class for maintaining replication state in zookeeper.
36   */
37  @InterfaceAudience.Private
38  public abstract class ReplicationStateZKBase {
39  
40    /**
41     * The name of the znode that contains the replication status of a remote slave (i.e. peer)
42     * cluster.
43     */
44    protected final String peerStateNodeName;
45    /** The name of the base znode that contains all replication state. */
46    protected final String replicationZNode;
47    /** The name of the znode that contains a list of all remote slave (i.e. peer) clusters. */
48    protected final String peersZNode;
49    /** The name of the znode that contains all replication queues */
50    protected final String queuesZNode;
51    /** The cluster key of the local cluster */
52    protected final String ourClusterKey;
53    protected final ZooKeeperWatcher zookeeper;
54    protected final Configuration conf;
55    protected final Abortable abortable;
56  
57    // Public for testing
58    public static final byte[] ENABLED_ZNODE_BYTES =
59        toByteArray(ZooKeeperProtos.ReplicationState.State.ENABLED);
60    public static final byte[] DISABLED_ZNODE_BYTES =
61        toByteArray(ZooKeeperProtos.ReplicationState.State.DISABLED);
62  
63    public ReplicationStateZKBase(ZooKeeperWatcher zookeeper, Configuration conf,
64        Abortable abortable) {
65      this.zookeeper = zookeeper;
66      this.conf = conf;
67      this.abortable = abortable;
68  
69      String replicationZNodeName = conf.get("zookeeper.znode.replication", "replication");
70      String peersZNodeName = conf.get("zookeeper.znode.replication.peers", "peers");
71      String queuesZNodeName = conf.get("zookeeper.znode.replication.rs", "rs");
72      this.peerStateNodeName = conf.get("zookeeper.znode.replication.peers.state", "peer-state");
73      this.ourClusterKey = ZKConfig.getZooKeeperClusterKey(this.conf);
74      this.replicationZNode = ZKUtil.joinZNode(this.zookeeper.baseZNode, replicationZNodeName);
75      this.peersZNode = ZKUtil.joinZNode(replicationZNode, peersZNodeName);
76      this.queuesZNode = ZKUtil.joinZNode(replicationZNode, queuesZNodeName);
77    }
78  
79    public List<String> getListOfReplicators() {
80      List<String> result = null;
81      try {
82        result = ZKUtil.listChildrenNoWatch(this.zookeeper, this.queuesZNode);
83      } catch (KeeperException e) {
84        this.abortable.abort("Failed to get list of replicators", e);
85      }
86      return result;
87    }
88  
89    /**
90     * @param state
91     * @return Serialized protobuf of <code>state</code> with pb magic prefix prepended suitable for
92     *         use as content of a peer-state znode under a peer cluster id as in
93     *         /hbase/replication/peers/PEER_ID/peer-state.
94     */
95    protected static byte[] toByteArray(final ZooKeeperProtos.ReplicationState.State state) {
96      byte[] bytes =
97          ZooKeeperProtos.ReplicationState.newBuilder().setState(state).build().toByteArray();
98      return ProtobufUtil.prependPBMagic(bytes);
99    }
100 
101   protected boolean peerExists(String id) throws KeeperException {
102     return ZKUtil.checkExists(this.zookeeper, ZKUtil.joinZNode(this.peersZNode, id)) >= 0;
103   }
104 
105   /**
106    * Determine if a ZK path points to a peer node.
107    * @param path path to be checked
108    * @return true if the path points to a peer node, otherwise false
109    */
110   protected boolean isPeerPath(String path) {
111     return path.split("/").length == peersZNode.split("/").length + 1;
112   }
113 }