/**
    *
    * 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;
  
  import java.io.IOException;
  import java.io.InterruptedIOException;
  import java.util.ArrayList;
  import java.util.List;
  import java.util.NavigableMap;
  import java.util.TreeMap;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.hadoop.hbase.Server;
  import org.apache.hadoop.hbase.ServerName;
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.hbase.master.ServerManager;
  import org.apache.hadoop.hbase.protobuf.ProtobufUtil;
  import org.apache.hadoop.hbase.protobuf.generated.HBaseProtos.RegionServerInfo;
  import org.apache.zookeeper.KeeperException;
  
  /**
   * Tracks the online region servers via ZK.
   *
   * <p>Handling of new RSs checking in is done via RPC.  This class
   * is only responsible for watching for expired nodes.  It handles
   * listening for changes in the RS node list and watching each node.
   *
   * <p>If an RS node gets deleted, this automatically handles calling of
   * {@link ServerManager#expireServer(ServerName)}
   */
  @InterfaceAudience.Private
  public class RegionServerTracker extends ZooKeeperListener {
    private static final Log LOG = LogFactory.getLog(RegionServerTracker.class);
    private NavigableMap<ServerName, RegionServerInfo> regionServers = 
        new TreeMap<ServerName, RegionServerInfo>();
    private ServerManager serverManager;
    private Server server;
  
    public RegionServerTracker(ZooKeeperWatcher watcher,
        Server server, ServerManager serverManager) {
      super(watcher);
      this.server = server;
      this.serverManager = serverManager;
    }
  
    /**
     * Starts the tracking of online RegionServers.
     *
     * <p>All RSs will be tracked after this method is called.
     *
     * @throws KeeperException
     * @throws IOException
     */
    public void start() throws KeeperException, IOException {
      watcher.registerListener(this);
      List<String> servers =
        ZKUtil.listChildrenAndWatchThem(watcher, watcher.rsZNode);
      add(servers);
    }
  
    private void add(final List<String> servers) throws IOException {
      synchronized(this.regionServers) {
        this.regionServers.clear();
        for (String n: servers) {
          ServerName sn = ServerName.parseServerName(ZKUtil.getNodeName(n));
          if (regionServers.get(sn) == null) {
            RegionServerInfo.Builder rsInfoBuilder = RegionServerInfo.newBuilder();
            try {
              String nodePath = ZKUtil.joinZNode(watcher.rsZNode, n);
              byte[] data = ZKUtil.getData(watcher, nodePath);
              if (data != null && data.length > 0 && ProtobufUtil.isPBMagicPrefix(data)) {
                int magicLen = ProtobufUtil.lengthOfPBMagic();
                ProtobufUtil.mergeFrom(rsInfoBuilder, data, magicLen, data.length - magicLen);
              }
              if (LOG.isDebugEnabled()) {
                LOG.debug("Added tracking of RS " + nodePath);
              }
            } catch (KeeperException e) {
              LOG.warn("Get Rs info port from ephemeral node", e);
            } catch (IOException e) {
              LOG.warn("Illegal data from ephemeral node", e);
            } catch (InterruptedException e) {
             throw new InterruptedIOException();
           }
           this.regionServers.put(sn, rsInfoBuilder.build());
         }
       }
     }
   }
 
   private void remove(final ServerName sn) {
     synchronized(this.regionServers) {
       this.regionServers.remove(sn);
     }
   }
 
   @Override
   public void nodeDeleted(String path) {
     if (path.startsWith(watcher.rsZNode)) {
       String serverName = ZKUtil.getNodeName(path);
       LOG.info("RegionServer ephemeral node deleted, processing expiration [" +
         serverName + "]");
       ServerName sn = ServerName.parseServerName(serverName);
       if (!serverManager.isServerOnline(sn)) {
         LOG.warn(serverName.toString() + " is not online or isn't known to the master."+
          "The latter could be caused by a DNS misconfiguration.");
         return;
       }
       remove(sn);
       this.serverManager.expireServer(sn);
     }
   }
 
   @Override
   public void nodeChildrenChanged(String path) {
     if (path.equals(watcher.rsZNode)
         && !server.isAborted() && !server.isStopped()) {
       try {
         List<String> servers =
           ZKUtil.listChildrenAndWatchThem(watcher, watcher.rsZNode);
         add(servers);
       } catch (IOException e) {
         server.abort("Unexpected zk exception getting RS nodes", e);
       } catch (KeeperException e) {
         server.abort("Unexpected zk exception getting RS nodes", e);
       }
     }
   }
 
   public RegionServerInfo getRegionServerInfo(final ServerName sn) {
     return regionServers.get(sn);
   }
   
   /**
    * Gets the online servers.
    * @return list of online servers
    */
   public List<ServerName> getOnlineServers() {
     synchronized (this.regionServers) {
       return new ArrayList<ServerName>(this.regionServers.keySet());
     }
   }
 }