package org.apache.helix.manager.zk;
/*
* 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.
*/
import java.util.List;
import org.I0Itec.zkclient.exception.ZkNoNodeException;
import org.apache.helix.AccessOption;
import org.apache.helix.BaseDataAccessor;
import org.apache.helix.store.zk.ZNode;
import org.apache.helix.util.HelixUtil;
import org.apache.log4j.Logger;
import org.apache.zookeeper.data.Stat;
public class WriteThroughCache<T> extends Cache<T> {
private static Logger LOG = Logger.getLogger(WriteThroughCache.class);
final BaseDataAccessor<T> _accessor;
public WriteThroughCache(BaseDataAccessor<T> accessor, List<String> paths) {
super();
_accessor = accessor;
// init cache
if (paths != null && !paths.isEmpty()) {
for (String path : paths) {
updateRecursive(path);
}
}
}
@Override
public void update(String path, T data, Stat stat) {
String parentPath = HelixUtil.getZkParentPath(path);
String childName = HelixUtil.getZkName(path);
addToParentChildSet(parentPath, childName);
ZNode znode = _cache.get(path);
if (znode == null) {
_cache.put(path, new ZNode(path, data, stat));
} else {
znode.setData(data);
znode.setStat(stat);
}
}
@Override
public void updateRecursive(String path) {
if (path == null) {
return;
}
try {
_lock.writeLock().lock();
// update this node
Stat stat = new Stat();
T readData = _accessor.get(path, stat, AccessOption.THROW_EXCEPTION_IFNOTEXIST);
update(path, readData, stat);
// recursively update children nodes if not exists
ZNode znode = _cache.get(path);
List<String> childNames = _accessor.getChildNames(path, 0);
if (childNames != null && childNames.size() > 0) {
for (String childName : childNames) {
String childPath = path + "/" + childName;
if (!znode.hasChild(childName)) {
znode.addChild(childName);
updateRecursive(childPath);
}
}
}
} catch (ZkNoNodeException e) {
// OK. someone delete znode while we are updating cache
} finally {
_lock.writeLock().unlock();
}
}
}