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1   /**
2    * Copyright The Apache Software Foundation
3    *
4    * Licensed to the Apache Software Foundation (ASF) under one
5    * or more contributor license agreements.  See the NOTICE file
6    * distributed with this work for additional information
7    * regarding copyright ownership.  The ASF licenses this file
8    * to you under the Apache License, Version 2.0 (the
9    * "License"); you may not use this file except in compliance
10   * with the License.  You may obtain a copy of the License at
11   *
12   *     http://www.apache.org/licenses/LICENSE-2.0
13   *
14   * Unless required by applicable law or agreed to in writing, software
15   * distributed under the License is distributed on an "AS IS" BASIS,
16   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
17   * See the License for the specific language governing permissions and
18   * limitations under the License.
19   */
20  package org.apache.hadoop.hbase.zookeeper.lock;
21  
22  import java.io.IOException;
23  import java.util.List;
24  import java.util.TreeSet;
25  
26  import org.apache.commons.logging.Log;
27  import org.apache.commons.logging.LogFactory;
28  import org.apache.hadoop.classification.InterfaceAudience;
29  import org.apache.hadoop.hbase.zookeeper.ZKUtil;
30  import org.apache.hadoop.hbase.zookeeper.ZooKeeperWatcher;
31  
32  /**
33   * ZooKeeper based write lock:
34   */
35  @InterfaceAudience.Private
36  public class ZKInterProcessWriteLock extends ZKInterProcessLockBase {
37  
38    private static final Log LOG = LogFactory.getLog(ZKInterProcessWriteLock.class);
39  
40    public ZKInterProcessWriteLock(ZooKeeperWatcher zooKeeperWatcher,
41        String znode, byte[] metadata, MetadataHandler handler) {
42      super(zooKeeperWatcher, znode, metadata, handler, WRITE_LOCK_CHILD_NODE_PREFIX);
43    }
44  
45    /**
46     * {@inheritDoc}
47     */
48    @Override
49    protected String getLockPath(String createdZNode, List<String> children) throws IOException {
50      TreeSet<String> sortedChildren =
51          new TreeSet<String>(ZNodeComparator.COMPARATOR);
52      sortedChildren.addAll(children);
53      String pathToWatch = sortedChildren.lower(createdZNode);
54      if (pathToWatch != null) {
55        String nodeHoldingLock = sortedChildren.first();
56        String znode = ZKUtil.joinZNode(parentLockNode, nodeHoldingLock);
57        handleLockMetadata(znode);
58      }
59      return pathToWatch;
60    }
61  }