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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.regionserver.handler;

import java.io.IOException;
import org.apache.hadoop.hbase.Server;
import org.apache.hadoop.hbase.ServerName;
import org.apache.hadoop.hbase.client.RegionInfo;
import org.apache.hadoop.hbase.executor.EventHandler;
import org.apache.hadoop.hbase.executor.EventType;
import org.apache.hadoop.hbase.procedure2.Procedure;
import org.apache.hadoop.hbase.regionserver.HRegion;
import org.apache.hadoop.hbase.regionserver.RegionServerServices;
import org.apache.hadoop.hbase.regionserver.RegionServerServices.RegionStateTransitionContext;
import org.apache.yetus.audience.InterfaceAudience;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import org.apache.hadoop.hbase.shaded.protobuf.generated.RegionServerStatusProtos.RegionStateTransition.TransitionCode;

/**
 * Handles closing of a region on a region server.
 * <p/>
 * In normal operation, we use {@link UnassignRegionHandler} closing Regions but when shutting down
 * the region server and closing out Regions, we use this handler instead; it does not expect to be
 * able to communicate the close back to the Master.
 * <p>
 * Expects that the close *has* been registered in the hosting RegionServer before submitting this
 * Handler; i.e. <code>rss.getRegionsInTransitionInRS().putIfAbsent(
 * this.regionInfo.getEncodedNameAsBytes(), Boolean.FALSE);</code> has been called first. In here
 * when done, we do the deregister.
 * </p>
 * @see UnassignRegionHandler
 */
@InterfaceAudience.Private
public class CloseRegionHandler extends EventHandler {
  // NOTE on priorities shutting down. There are none for close. There are some
  // for open. I think that is right. On shutdown, we want the meta to close
  // after the user regions have closed. What
  // about the case where master tells us to shutdown a catalog region and we
  // have a running queue of user regions to close?
  private static final Logger LOG = LoggerFactory.getLogger(CloseRegionHandler.class);

  private final RegionServerServices rsServices;
  private final RegionInfo regionInfo;

  // If true, the hosting server is aborting. Region close process is different
  // when we are aborting.
  private final boolean abort;
  private ServerName destination;

  /**
   * This method used internally by the RegionServer to close out regions.
   * @param abort If the regionserver is aborting.
   */
  public CloseRegionHandler(final Server server, final RegionServerServices rsServices,
    final RegionInfo regionInfo, final boolean abort, ServerName destination) {
    this(server, rsServices, regionInfo, abort, EventType.M_RS_CLOSE_REGION, destination);
  }

  protected CloseRegionHandler(final Server server, final RegionServerServices rsServices,
    RegionInfo regionInfo, boolean abort, EventType eventType, ServerName destination) {
    super(server, eventType);
    this.server = server;
    this.rsServices = rsServices;
    this.regionInfo = regionInfo;
    this.abort = abort;
    this.destination = destination;
  }

  public RegionInfo getRegionInfo() {
    return regionInfo;
  }

  @Override
  public void process() throws IOException {
    String name = regionInfo.getEncodedName();
    LOG.trace("Processing close of {}", name);
    // Check that this region is being served here
    HRegion region = (HRegion) rsServices.getRegion(name);
    try {
      if (region == null) {
        LOG.warn("Received CLOSE for region {} but currently not serving - ignoring", name);
        // TODO: do better than a simple warning
        return;
      }

      // Close the region
      if (region.close(abort, false, true) == null) {
        // This region has already been closed. Should not happen (A unit test makes this
        // happen as a side effect, TestRegionObserverInterface.testPreWALAppendNotCalledOnMetaEdit)
        LOG.warn("Can't close {}; already closed", name);
        return;
      }

      this.rsServices.removeRegion(region, destination);
      // Report the region's durable flushed seqid on CLOSE so the master can seed its
      // flushedSequenceIdByRegion watermark. This complements the OPEN-time seed (HBASE-30335)
      // and narrows the graceful-close window where a subsequent WAL split of a crashed source
      // RS could otherwise write orphaned recovered.edits for already-durable edits.
      rsServices.reportRegionStateTransition(new RegionStateTransitionContext(TransitionCode.CLOSED,
        region.getMaxFlushedSeqId(), Procedure.NO_PROC_ID, -1, regionInfo, -1));

      // Done! Region is closed on this RS
      LOG.debug("Closed {}", region.getRegionInfo().getRegionNameAsString());
    } finally {
      // Clear any reference in getServer().getRegionsInTransitionInRS() on success or failure,
      // since a reference was added before this CRH was invoked. If we don't clear it, it can
      // hold up regionserver abort on cluster shutdown. HBASE-23984.
      this.rsServices.getRegionsInTransitionInRS().remove(regionInfo.getEncodedNameAsBytes());
    }
  }

  @Override
  protected void handleException(Throwable t) {
    server.abort("Unrecoverable exception while closing " + this.regionInfo.getRegionNameAsString(),
      t);
  }
}