/**
    *
    * 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.cleaner;
  
  import java.util.HashSet;
  import java.util.List;
  import java.util.Set;
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.hadoop.conf.Configuration;
  import org.apache.hadoop.hbase.Abortable;
  import org.apache.hadoop.hbase.ScheduledChore;
  import org.apache.hadoop.hbase.Stoppable;
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.hbase.replication.ReplicationException;
  import org.apache.hadoop.hbase.replication.ReplicationFactory;
  import org.apache.hadoop.hbase.replication.ReplicationQueuesZKImpl;
  import org.apache.hadoop.hbase.replication.ReplicationTracker;
  import org.apache.hadoop.hbase.util.Bytes;
  import org.apache.hadoop.hbase.util.EnvironmentEdgeManager;
  import org.apache.hadoop.hbase.zookeeper.ZKUtil;
  import org.apache.hadoop.hbase.zookeeper.ZooKeeperWatcher;
  import org.apache.zookeeper.KeeperException;
  import org.apache.zookeeper.data.Stat;
  
  /**
   * A cleaner that cleans replication locks on zk which is locked by dead region servers
   */
  @InterfaceAudience.Private
  public class ReplicationZKLockCleanerChore extends ScheduledChore {
    private static final Log LOG = LogFactory.getLog(ReplicationZKLockCleanerChore.class);
    private ZooKeeperWatcher zk;
    private ReplicationTracker tracker;
    private long ttl;
    private ReplicationQueuesZKImpl queues;
  
    // Wait some times before delete lock to prevent a session expired RS not dead fully.
    private static final long DEFAULT_TTL = 60 * 10 * 1000;//10 min
  
    public static final String TTL_CONFIG_KEY = "hbase.replication.zk.deadrs.lock.ttl";
  
    public ReplicationZKLockCleanerChore(Stoppable stopper, Abortable abortable, int period,
        ZooKeeperWatcher zk, Configuration conf) throws Exception {
      super("ReplicationZKLockCleanerChore", stopper, period);
  
      this.zk = zk;
      this.ttl = conf.getLong(TTL_CONFIG_KEY, DEFAULT_TTL);
      tracker = ReplicationFactory.getReplicationTracker(zk,
          ReplicationFactory.getReplicationPeers(zk, conf, abortable), conf, abortable, stopper);
      queues = new ReplicationQueuesZKImpl(zk, conf, abortable);
    }
  
    @Override protected void chore() {
      try {
        List<String> regionServers = tracker.getListOfRegionServers();
        if (regionServers == null) {
          return;
        }
        Set<String> rsSet = new HashSet<String>(regionServers);
        List<String> replicators = queues.getListOfReplicators();
        if (replicators == null || replicators.isEmpty()) {
          return;
        }
        for (String replicator: replicators) {
          try {
            String lockNode = queues.getLockZNode(replicator);
            byte[] data = ZKUtil.getData(zk, lockNode);
            if (data == null) {
              continue;
            }
            String rsServerNameZnode = Bytes.toString(data);
            String[] array = rsServerNameZnode.split("/");
            String znode = array[array.length - 1];
            if (!rsSet.contains(znode)) {
              Stat s = zk.getRecoverableZooKeeper().exists(lockNode, false);
              if (s != null && EnvironmentEdgeManager.currentTime() - s.getMtime() > this.ttl) {
                // server is dead, but lock is still there, we have to delete the lock.
                ZKUtil.deleteNode(zk, lockNode);
                LOG.info("Remove lock acquired by dead RS: " + lockNode + " by " + znode);
              }
              continue;
            }
            LOG.info("Skip lock acquired by live RS: " + lockNode + " by " + znode);
 
         } catch (KeeperException.NoNodeException ignore) {
         } catch (InterruptedException e) {
           LOG.warn("zk operation interrupted", e);
           Thread.currentThread().interrupt();
         }
       }
     } catch (KeeperException e) {
       LOG.warn("zk operation interrupted", e);
     } catch (ReplicationException e2) {
       LOG.warn("replication exception", e2);
     }
   }
 }