/**
* Copyright The Apache Software Foundation
*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.hadoop.hbase.zookeeper.lock;
import java.io.IOException;
import java.util.List;
import java.util.TreeSet;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.hbase.zookeeper.ZKUtil;
import org.apache.hadoop.hbase.zookeeper.ZooKeeperWatcher;
import org.apache.zookeeper.KeeperException;
/**
* ZooKeeper based write lock:
*/
@InterfaceAudience.Private
public class ZKInterProcessWriteLock extends ZKInterProcessLockBase {
private static final Log LOG = LogFactory.getLog(ZKInterProcessWriteLock.class);
public ZKInterProcessWriteLock(ZooKeeperWatcher zooKeeperWatcher,
String znode, byte[] metadata, MetadataHandler handler) {
super(zooKeeperWatcher, znode, metadata, handler, WRITE_LOCK_CHILD_NODE_PREFIX);
}
/**
* {@inheritDoc}
*/
@Override
protected String getLockPath(String createdZNode, List<String> children)
throws IOException, InterruptedException {
TreeSet<String> sortedChildren =
new TreeSet<String>(ZNodeComparator.COMPARATOR);
sortedChildren.addAll(children);
String pathToWatch = sortedChildren.lower(createdZNode);
if (pathToWatch != null) {
String nodeHoldingLock = sortedChildren.first();
String znode = ZKUtil.joinZNode(parentLockNode, nodeHoldingLock);
try {
handleLockMetadata(znode);
} catch (IOException e) {
LOG.warn("Error processing lock metadata in " + nodeHoldingLock, e);
}
}
return pathToWatch;
}
/**
* Referred in zk recipe as "Revocable Shared Locks with Freaking Laser Beams"
* (http://zookeeper.apache.org/doc/trunk/recipes.html).
*/
public void reapAllLocks() throws IOException {
List<String> children;
try {
children = ZKUtil.listChildrenNoWatch(zkWatcher, parentLockNode);
} catch (KeeperException e) {
LOG.error("Unexpected ZooKeeper error when listing children", e);
throw new IOException("Unexpected ZooKeeper exception", e);
}
KeeperException deferred = null;
for (String child : children) {
if (isChildWriteLock(child)) {
String znode = ZKUtil.joinZNode(parentLockNode, child);
LOG.info("Reaping write lock for znode:" + znode);
try {
ZKUtil.deleteNodeFailSilent(zkWatcher, znode);
} catch (KeeperException ex) {
LOG.warn("Error reaping the znode for write lock :" + znode);
deferred = ex;
}
}
}
if (deferred != null) {
throw new IOException("ZK exception while reaping locks:", deferred);
}
}
}