/**
* 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 com.alibaba.wasp.zookeeper;
import com.alibaba.wasp.ServerName;
import com.alibaba.wasp.master.FServerManager;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.hbase.Abortable;
import org.apache.zookeeper.KeeperException;
import java.io.IOException;
import java.util.List;
import java.util.NavigableSet;
import java.util.TreeSet;
/**
* Tracks the list of draining fservers via ZK.
*
* <p>
* This class is responsible for watching for changes to the draining servers
* list. It handles adds/deletes in the draining FS list and watches each node.
*
* <p>
* If an fs gets deleted from draining list, we call
* {@link com.alibaba.wasp.master.FServerManager#removeServerFromDrainList(com.alibaba.wasp.ServerName)}
*
* <p>
* If an fs gets added to the draining list, we add a watcher to it and call
* {@link com.alibaba.wasp.master.FServerManager#addServerToDrainList(com.alibaba.wasp.ServerName)}
*
*/
public class DrainingServerTracker extends ZooKeeperListener {
private static final Log LOG = LogFactory.getLog(DrainingServerTracker.class);
private FServerManager serverManager;
private NavigableSet<ServerName> drainingServers = new TreeSet<ServerName>();
private Abortable abortable;
public DrainingServerTracker(ZooKeeperWatcher watcher,
Abortable abortable, FServerManager serverManager) {
super(watcher);
this.abortable = abortable;
this.serverManager = serverManager;
}
/**
* Starts the tracking of draining fServers.
*
* <p>All Draining RSs will be tracked after this method is called.
*
* @throws org.apache.zookeeper.KeeperException
*/
public void start() throws KeeperException, IOException {
watcher.registerListener(this);
List<String> servers =
ZKUtil.listChildrenAndWatchThem(watcher, watcher.drainingZNode);
add(servers);
}
private void add(final List<String> servers) throws IOException {
synchronized(this.drainingServers) {
this.drainingServers.clear();
for (String n: servers) {
final ServerName sn = new ServerName(ZKUtil.getNodeName(n));
this.drainingServers.add(sn);
this.serverManager.addServerToDrainList(sn);
LOG.info("Draining RS node created, adding to list [" +
sn + "]");
}
}
}
private void remove(final ServerName sn) {
synchronized(this.drainingServers) {
this.drainingServers.remove(sn);
this.serverManager.removeServerFromDrainList(sn);
}
}
@Override
public void nodeDeleted(final String path) {
if(path.startsWith(watcher.drainingZNode)) {
final ServerName sn = new ServerName(ZKUtil.getNodeName(path));
LOG.info("Draining RS node deleted, removing from list [" +
sn + "]");
remove(sn);
}
}
@Override
public void nodeChildrenChanged(final String path) {
if(path.equals(watcher.drainingZNode)) {
try {
final List<String> newNodes =
ZKUtil.listChildrenAndWatchThem(watcher, watcher.drainingZNode);
add(newNodes);
} catch (KeeperException e) {
abortable.abort("Unexpected zk exception getting RS nodes", e);
} catch (IOException e) {
abortable.abort("Unexpected zk exception getting RS nodes", e);
}
}
}
}