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/*
 * 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.master;

import java.io.IOException;
import java.util.List;
import java.util.NavigableSet;
import java.util.TreeSet;
import org.apache.hadoop.hbase.Abortable;
import org.apache.hadoop.hbase.ServerName;
import org.apache.hadoop.hbase.zookeeper.ZKListener;
import org.apache.hadoop.hbase.zookeeper.ZKUtil;
import org.apache.hadoop.hbase.zookeeper.ZKWatcher;
import org.apache.yetus.audience.InterfaceAudience;
import org.apache.zookeeper.KeeperException;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Tracks the list of draining region servers via ZK.
 * 

* This class is responsible for watching for changes to the draining servers list. It handles * adds/deletes in the draining RS list and watches each node. *

* If an RS gets deleted from draining list, we call * {@link ServerManager#removeServerFromDrainList(ServerName)} *

* If an RS gets added to the draining list, we add a watcher to it and call * {@link ServerManager#addServerToDrainList(ServerName)} *

* This class is deprecated in 2.0 because decommission/draining API goes through master in 2.0. Can * remove this class in 3.0. */ @InterfaceAudience.Private public class DrainingServerTracker extends ZKListener { private static final Logger LOG = LoggerFactory.getLogger(DrainingServerTracker.class); private ServerManager serverManager; private final NavigableSet drainingServers = new TreeSet<>(); private Abortable abortable; public DrainingServerTracker(ZKWatcher watcher, Abortable abortable, ServerManager serverManager) { super(watcher); this.abortable = abortable; this.serverManager = serverManager; } /** * Starts the tracking of draining RegionServers. *

* All Draining RSs will be tracked after this method is called. */ public void start() throws KeeperException, IOException { watcher.registerListener(this); // Add a ServerListener to check if a server is draining when it's added. serverManager.registerListener(new ServerListener() { @Override public void serverAdded(ServerName sn) { if (drainingServers.contains(sn)) { serverManager.addServerToDrainList(sn); } } }); List servers = ZKUtil.listChildrenAndWatchThem(watcher, watcher.getZNodePaths().drainingZNode); add(servers); } private void add(final List servers) throws IOException { synchronized (this.drainingServers) { this.drainingServers.clear(); for (String n : servers) { final ServerName sn = ServerName.valueOf(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.getZNodePaths().drainingZNode)) { final ServerName sn = ServerName.valueOf(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.getZNodePaths().drainingZNode)) { try { final List newNodes = ZKUtil.listChildrenAndWatchThem(watcher, watcher.getZNodePaths().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); } } } }





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