/**
    *
    * 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.handler;
  
  import java.io.IOException;
  import java.io.InterruptedIOException;
  import java.util.ArrayList;
  import java.util.List;
  import java.util.Set;
  import java.util.concurrent.locks.Lock;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.hadoop.hbase.HConstants;
  import org.apache.hadoop.hbase.HRegionInfo;
  import org.apache.hadoop.hbase.MetaTableAccessor;
  import org.apache.hadoop.hbase.Server;
  import org.apache.hadoop.hbase.ServerName;
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.hbase.client.RegionReplicaUtil;
  import org.apache.hadoop.hbase.executor.EventHandler;
  import org.apache.hadoop.hbase.executor.EventType;
  import org.apache.hadoop.hbase.master.AssignmentManager;
  import org.apache.hadoop.hbase.master.DeadServer;
  import org.apache.hadoop.hbase.master.MasterFileSystem;
  import org.apache.hadoop.hbase.master.MasterServices;
  import org.apache.hadoop.hbase.master.RegionState;
  import org.apache.hadoop.hbase.master.RegionState.State;
  import org.apache.hadoop.hbase.master.RegionStates;
  import org.apache.hadoop.hbase.master.ServerManager;
  import org.apache.hadoop.hbase.master.balancer.BaseLoadBalancer;
  import org.apache.hadoop.hbase.protobuf.generated.ZooKeeperProtos;
  import org.apache.hadoop.hbase.protobuf.generated.ZooKeeperProtos.SplitLogTask.RecoveryMode;
  import org.apache.hadoop.hbase.util.ConfigUtil;
  import org.apache.hadoop.hbase.zookeeper.ZKAssign;
  import org.apache.zookeeper.KeeperException;
  
  /**
   * Process server shutdown.
   * Server-to-handle must be already in the deadservers lists.  See
   * {@link ServerManager#expireServer(ServerName)}
   */
  @InterfaceAudience.Private
  public class ServerShutdownHandler extends EventHandler {
    private static final Log LOG = LogFactory.getLog(ServerShutdownHandler.class);
    protected final ServerName serverName;
    protected final MasterServices services;
    protected final DeadServer deadServers;
    protected final boolean shouldSplitWal; // whether to split WAL or not
    protected final int regionAssignmentWaitTimeout;
  
    public ServerShutdownHandler(final Server server, final MasterServices services,
        final DeadServer deadServers, final ServerName serverName,
        final boolean shouldSplitWal) {
      this(server, services, deadServers, serverName, EventType.M_SERVER_SHUTDOWN,
          shouldSplitWal);
    }
  
    ServerShutdownHandler(final Server server, final MasterServices services,
        final DeadServer deadServers, final ServerName serverName, EventType type,
        final boolean shouldSplitWal) {
      super(server, type);
      this.serverName = serverName;
      this.server = server;
      this.services = services;
      this.deadServers = deadServers;
      if (!this.deadServers.isDeadServer(this.serverName)) {
        LOG.warn(this.serverName + " is NOT in deadservers; it should be!");
      }
      this.shouldSplitWal = shouldSplitWal;
      this.regionAssignmentWaitTimeout = server.getConfiguration().getInt(
        HConstants.LOG_REPLAY_WAIT_REGION_TIMEOUT, 15000);
    }
  
    @Override
    public String getInformativeName() {
      if (serverName != null) {
        return this.getClass().getSimpleName() + " for " + serverName;
      } else {
        return super.getInformativeName();
      }
    }
  
   /**
    * @return True if the server we are processing was carrying <code>hbase:meta</code>
    */
   boolean isCarryingMeta() {
     return false;
   }
 
   @Override
   public String toString() {
     return getClass().getSimpleName() + "-" + serverName + "-" + getSeqid();
   }
 
   @Override
   public void process() throws IOException {
     boolean hasLogReplayWork = false;
     final ServerName serverName = this.serverName;
     try {
 
       // We don't want worker thread in the MetaServerShutdownHandler
       // executor pool to block by waiting availability of hbase:meta
       // Otherwise, it could run into the following issue:
       // 1. The current MetaServerShutdownHandler instance For RS1 waits for the hbase:meta
       //    to come online.
       // 2. The newly assigned hbase:meta region server RS2 was shutdown right after
       //    it opens the hbase:meta region. So the MetaServerShutdownHandler
       //    instance For RS1 will still be blocked.
       // 3. The new instance of MetaServerShutdownHandler for RS2 is queued.
       // 4. The newly assigned hbase:meta region server RS3 was shutdown right after
       //    it opens the hbase:meta region. So the MetaServerShutdownHandler
       //    instance For RS1 and RS2 will still be blocked.
       // 5. The new instance of MetaServerShutdownHandler for RS3 is queued.
       // 6. Repeat until we run out of MetaServerShutdownHandler worker threads
       // The solution here is to resubmit a ServerShutdownHandler request to process
       // user regions on that server so that MetaServerShutdownHandler
       // executor pool is always available.
       //
       // If AssignmentManager hasn't finished rebuilding user regions,
       // we are not ready to assign dead regions either. So we re-queue up
       // the dead server for further processing too.
       AssignmentManager am = services.getAssignmentManager();
       ServerManager serverManager = services.getServerManager();
       if (isCarryingMeta() /* hbase:meta */ || !am.isFailoverCleanupDone()) {
         serverManager.processDeadServer(serverName, this.shouldSplitWal);
         return;
       }
 
       // Wait on meta to come online; we need it to progress.
       // TODO: Best way to hold strictly here?  We should build this retry logic
       // into the MetaTableAccessor operations themselves.
       // TODO: Is the reading of hbase:meta necessary when the Master has state of
       // cluster in its head?  It should be possible to do without reading hbase:meta
       // in all but one case. On split, the RS updates the hbase:meta
       // table and THEN informs the master of the split via zk nodes in
       // 'unassigned' dir.  Currently the RS puts ephemeral nodes into zk so if
       // the regionserver dies, these nodes do not stick around and this server
       // shutdown processing does fixup (see the fixupDaughters method below).
       // If we wanted to skip the hbase:meta scan, we'd have to change at least the
       // final SPLIT message to be permanent in zk so in here we'd know a SPLIT
       // completed (zk is updated after edits to hbase:meta have gone in).  See
       // {@link SplitTransaction}.  We'd also have to be figure another way for
       // doing the below hbase:meta daughters fixup.
       Set<HRegionInfo> hris = null;
       while (!this.server.isStopped()) {
         try {
           server.getMetaTableLocator().waitMetaRegionLocation(server.getZooKeeper());
           if (BaseLoadBalancer.tablesOnMaster(server.getConfiguration())) {
             while (!this.server.isStopped() && serverManager.countOfRegionServers() < 2) {
               // Wait till at least another regionserver is up besides the active master
               // so that we don't assign all regions to the active master.
               // This is best of efforts, because newly joined regionserver
               // could crash right after that.
               Thread.sleep(100);
             }
           }
           // Skip getting user regions if the server is stopped.
           if (!this.server.isStopped()) {
             if (ConfigUtil.useZKForAssignment(server.getConfiguration())) {
               hris = MetaTableAccessor.getServerUserRegions(this.server.getConnection(),
                 this.serverName).keySet();
             } else {
               // Not using ZK for assignment, regionStates has everything we want
               hris = am.getRegionStates().getServerRegions(serverName);
             }
           }
           break;
         } catch (InterruptedException e) {
           Thread.currentThread().interrupt();
           throw (InterruptedIOException)new InterruptedIOException().initCause(e);
         } catch (IOException ioe) {
           LOG.info("Received exception accessing hbase:meta during server shutdown of " +
             serverName + ", retrying hbase:meta read", ioe);
         }
       }
       if (this.server.isStopped()) {
         throw new IOException("Server is stopped");
       }
 
       // delayed to set recovery mode based on configuration only after all outstanding splitlogtask
       // drained
       this.services.getMasterFileSystem().setLogRecoveryMode();
       boolean distributedLogReplay = 
         (this.services.getMasterFileSystem().getLogRecoveryMode() == RecoveryMode.LOG_REPLAY);
 
       try {
         if (this.shouldSplitWal) {
           if (distributedLogReplay) {
             LOG.info("Mark regions in recovery for crashed server " + serverName +
               " before assignment; regions=" + hris);
             MasterFileSystem mfs = this.services.getMasterFileSystem();
             mfs.prepareLogReplay(serverName, hris);
           } else {
             LOG.info("Splitting logs for " + serverName +
               " before assignment; region count=" + (hris == null ? 0 : hris.size()));
             this.services.getMasterFileSystem().splitLog(serverName);
           }
           am.getRegionStates().logSplit(serverName);
         } else {
           LOG.info("Skipping log splitting for " + serverName);
         }
       } catch (IOException ioe) {
         resubmit(serverName, ioe);
       }
       List<HRegionInfo> toAssignRegions = new ArrayList<HRegionInfo>();
       int replicaCount = services.getConfiguration().getInt(HConstants.META_REPLICAS_NUM,
           HConstants.DEFAULT_META_REPLICA_NUM);
       for (int i = 1; i < replicaCount; i++) {
         HRegionInfo metaHri =
             RegionReplicaUtil.getRegionInfoForReplica(HRegionInfo.FIRST_META_REGIONINFO, i);
         if (am.isCarryingMetaReplica(serverName, metaHri) ==
             AssignmentManager.ServerHostRegion.HOSTING_REGION) {
           LOG.info("Reassigning meta replica" + metaHri + " that was on " + serverName);
           toAssignRegions.add(metaHri);
         }
       }
       // Clean out anything in regions in transition.  Being conservative and
       // doing after log splitting.  Could do some states before -- OPENING?
       // OFFLINE? -- and then others after like CLOSING that depend on log
       // splitting.
       List<HRegionInfo> regionsInTransition = am.processServerShutdown(serverName);
       LOG.info("Reassigning " + ((hris == null)? 0: hris.size()) +
         " region(s) that " + (serverName == null? "null": serverName)  +
         " was carrying (and " + regionsInTransition.size() +
         " regions(s) that were opening on this server)");
       
       toAssignRegions.addAll(regionsInTransition);
 
       // Iterate regions that were on this server and assign them
       if (hris != null && !hris.isEmpty()) {
         RegionStates regionStates = am.getRegionStates();
         for (HRegionInfo hri: hris) {
           if (regionsInTransition.contains(hri)) {
             continue;
           }
           String encodedName = hri.getEncodedName();
           Lock lock = am.acquireRegionLock(encodedName);
           try {
             RegionState rit = regionStates.getRegionTransitionState(hri);
             if (processDeadRegion(hri, am)) { 
               ServerName addressFromAM = regionStates.getRegionServerOfRegion(hri);
               if (addressFromAM != null && !addressFromAM.equals(this.serverName)) {
                 // If this region is in transition on the dead server, it must be
                 // opening or pending_open, which should have been covered by AM#processServerShutdown
                 LOG.info("Skip assigning region " + hri.getRegionNameAsString()
                   + " because it has been opened in " + addressFromAM.getServerName());
                 continue;
               }
               if (rit != null) {
                 if (rit.getServerName() != null && !rit.isOnServer(serverName)) {
                   // Skip regions that are in transition on other server
                   LOG.info("Skip assigning region in transition on other server" + rit);
                   continue;
                 }
                 try{
                   //clean zk node
                   LOG.info("Reassigning region with rs = " + rit + " and deleting zk node if exists");
                   ZKAssign.deleteNodeFailSilent(services.getZooKeeper(), hri);
                   regionStates.updateRegionState(hri, State.OFFLINE);
                 } catch (KeeperException ke) {
                   this.server.abort("Unexpected ZK exception deleting unassigned node " + hri, ke);
                   return;
                 }
               } else if (regionStates.isRegionInState(
                   hri, State.SPLITTING_NEW, State.MERGING_NEW)) {
                 regionStates.updateRegionState(hri, State.OFFLINE);
               }
               toAssignRegions.add(hri);
             } else if (rit != null) {
               if ((rit.isPendingCloseOrClosing() || rit.isOffline())
                   && am.getTableStateManager().isTableState(hri.getTable(),
                   ZooKeeperProtos.Table.State.DISABLED, ZooKeeperProtos.Table.State.DISABLING) ||
                   am.getReplicasToClose().contains(hri)) {
                 // If the table was partially disabled and the RS went down, we should clear the RIT
                 // and remove the node for the region.
                 // The rit that we use may be stale in case the table was in DISABLING state
                 // but though we did assign we will not be clearing the znode in CLOSING state.
                 // Doing this will have no harm. See HBASE-5927
                 regionStates.updateRegionState(hri, State.OFFLINE);
                 am.deleteClosingOrClosedNode(hri, rit.getServerName());
                 am.offlineDisabledRegion(hri);
               } else {
                 LOG.warn("THIS SHOULD NOT HAPPEN: unexpected region in transition "
                   + rit + " not to be assigned by SSH of server " + serverName);
               }
             }
           } finally {
             lock.unlock();
           }
         }
       }
 
       try {
         am.assign(toAssignRegions);
       } catch (InterruptedException ie) {
         LOG.error("Caught " + ie + " during round-robin assignment");
         throw (InterruptedIOException)new InterruptedIOException().initCause(ie);
       } catch (IOException ioe) {
         LOG.info("Caught " + ioe + " during region assignment, will retry");
         // Only do wal splitting if shouldSplitWal and in DLR mode
         serverManager.processDeadServer(serverName,
           this.shouldSplitWal && distributedLogReplay);
         return;
       }
 
       if (this.shouldSplitWal && distributedLogReplay) {
         // wait for region assignment completes
         for (HRegionInfo hri : toAssignRegions) {
           try {
             if (!am.waitOnRegionToClearRegionsInTransition(hri, regionAssignmentWaitTimeout)) {
               // Wait here is to avoid log replay hits current dead server and incur a RPC timeout
               // when replay happens before region assignment completes.
               LOG.warn("Region " + hri.getEncodedName()
                   + " didn't complete assignment in time");
             }
           } catch (InterruptedException ie) {
             throw new InterruptedIOException("Caught " + ie
                 + " during waitOnRegionToClearRegionsInTransition");
           }
         }
         // submit logReplay work
         this.services.getExecutorService().submit(
           new LogReplayHandler(this.server, this.services, this.deadServers, this.serverName));
         hasLogReplayWork = true;
       }
     } finally {
       this.deadServers.finish(serverName);
     }
 
     if (!hasLogReplayWork) {
       LOG.info("Finished processing of shutdown of " + serverName);
     }
   }
 
   private void resubmit(final ServerName serverName, IOException ex) throws IOException {
     // typecast to SSH so that we make sure that it is the SSH instance that
     // gets submitted as opposed to MSSH or some other derived instance of SSH
     this.services.getExecutorService().submit((ServerShutdownHandler) this);
     this.deadServers.add(serverName);
     throw new IOException("failed log splitting for " + serverName + ", will retry", ex);
   }
 
   /**
    * Process a dead region from a dead RS. Checks if the region is disabled or
    * disabling or if the region has a partially completed split.
    * @param hri
    * @param assignmentManager
    * @return Returns true if specified region should be assigned, false if not.
    * @throws IOException
    */
   public static boolean processDeadRegion(HRegionInfo hri,
       AssignmentManager assignmentManager)
   throws IOException {
     boolean tablePresent = assignmentManager.getTableStateManager().isTablePresent(hri.getTable());
     if (!tablePresent) {
       LOG.info("The table " + hri.getTable()
           + " was deleted.  Hence not proceeding.");
       return false;
     }
     // If table is not disabled but the region is offlined,
     boolean disabled = assignmentManager.getTableStateManager().isTableState(hri.getTable(),
       ZooKeeperProtos.Table.State.DISABLED);
     if (disabled){
       LOG.info("The table " + hri.getTable()
           + " was disabled.  Hence not proceeding.");
       return false;
     }
     if (hri.isOffline() && hri.isSplit()) {
       //HBASE-7721: Split parent and daughters are inserted into hbase:meta as an atomic operation.
       //If the meta scanner saw the parent split, then it should see the daughters as assigned
       //to the dead server. We don't have to do anything.
       return false;
     }
     boolean disabling = assignmentManager.getTableStateManager().isTableState(hri.getTable(),
       ZooKeeperProtos.Table.State.DISABLING);
     if (disabling) {
       LOG.info("The table " + hri.getTable()
           + " is disabled.  Hence not assigning region" + hri.getEncodedName());
       return false;
     }
     return true;
   }
 }