/**
    * Copyright The Apache Software Foundation
    *
    * 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 limitationsME
   * under the License.
   */
  package org.apache.hadoop.hbase.regionserver;
  
  import java.io.IOException;
  import java.util.ArrayList;
  import java.util.List;
  import java.util.ListIterator;
  import java.util.Map;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.fs.Path;
  import org.apache.hadoop.hbase.HConstants;
  import org.apache.hadoop.hbase.HRegionInfo;
  import org.apache.hadoop.hbase.MetaMutationAnnotation;
  import org.apache.hadoop.hbase.Server;
  import org.apache.hadoop.hbase.ServerName;
  import org.apache.hadoop.hbase.MetaTableAccessor;
  import org.apache.hadoop.hbase.client.Delete;
  import org.apache.hadoop.hbase.client.HConnection;
  import org.apache.hadoop.hbase.client.Mutation;
  import org.apache.hadoop.hbase.client.Put;
  import org.apache.hadoop.hbase.coordination.BaseCoordinatedStateManager;
  import org.apache.hadoop.hbase.coordination.RegionMergeCoordination.RegionMergeDetails;
  import org.apache.hadoop.hbase.protobuf.generated.RegionServerStatusProtos.RegionStateTransition.TransitionCode;
  import org.apache.hadoop.hbase.regionserver.SplitTransaction.JournalEntry;
  import org.apache.hadoop.hbase.regionserver.SplitTransactionImpl.LoggingProgressable;
  import org.apache.hadoop.hbase.security.User;
  import org.apache.hadoop.hbase.util.Bytes;
  import org.apache.hadoop.hbase.util.ConfigUtil;
  import org.apache.hadoop.hbase.util.EnvironmentEdgeManager;
  import org.apache.hadoop.hbase.util.Pair;
  import org.apache.zookeeper.KeeperException;
  
  @InterfaceAudience.Private
  public class RegionMergeTransactionImpl implements RegionMergeTransaction {
    private static final Log LOG = LogFactory.getLog(RegionMergeTransactionImpl.class);
  
    // Merged region info
    private HRegionInfo mergedRegionInfo;
    // region_a sorts before region_b
    private final HRegion region_a;
    private final HRegion region_b;
    // merges dir is under region_a
    private final Path mergesdir;
    // We only merge adjacent regions if forcible is false
    private final boolean forcible;
    private boolean useCoordinationForAssignment;
    private final long masterSystemTime;
  
    /*
     * Transaction state for listener, only valid during execute and
     * rollback
     */
    private RegionMergeTransactionPhase currentPhase = RegionMergeTransactionPhase.STARTED;
    private Server server;
    private RegionServerServices rsServices;
  
    public static class JournalEntryImpl implements JournalEntry {
      private RegionMergeTransactionPhase type;
      private long timestamp;
  
      public JournalEntryImpl(RegionMergeTransactionPhase type) {
        this(type, EnvironmentEdgeManager.currentTime());
      }
  
      public JournalEntryImpl(RegionMergeTransactionPhase type, long timestamp) {
        this.type = type;
        this.timestamp = timestamp;
      }
  
      @Override
      public String toString() {
        StringBuilder sb = new StringBuilder();
        sb.append(type);
        sb.append(" at ");
        sb.append(timestamp);
        return sb.toString();
      }
  
      @Override
     public RegionMergeTransactionPhase getPhase() {
       return type;
     }
 
     @Override
     public long getTimeStamp() {
       return timestamp;
     }
   }
 
   /*
    * Journal of how far the merge transaction has progressed.
    */
   private final List<JournalEntry> journal = new ArrayList<JournalEntry>();
 
   /*
    * Listeners
    */
   private final ArrayList<TransactionListener> listeners = new ArrayList<TransactionListener>();
 
   private static IOException closedByOtherException = new IOException(
       "Failed to close region: already closed by another thread");
 
   private RegionServerCoprocessorHost rsCoprocessorHost = null;
 
   private RegionMergeDetails rmd;
 
   /**
    * Constructor
    * @param a region a to merge
    * @param b region b to merge
    * @param forcible if false, we will only merge adjacent regions
    */
   public RegionMergeTransactionImpl(final Region a, final Region b,
       final boolean forcible) {
     this(a, b, forcible, EnvironmentEdgeManager.currentTime());
   }
   /**
    * Constructor
    * @param a region a to merge
    * @param b region b to merge
    * @param forcible if false, we will only merge adjacent regions
    * @param masterSystemTime the time at the master side
    */
   public RegionMergeTransactionImpl(final Region a, final Region b,
       final boolean forcible, long masterSystemTime) {
     if (a.getRegionInfo().compareTo(b.getRegionInfo()) <= 0) {
       this.region_a = (HRegion)a;
       this.region_b = (HRegion)b;
     } else {
       this.region_a = (HRegion)b;
       this.region_b = (HRegion)a;
     }
     this.forcible = forcible;
     this.masterSystemTime = masterSystemTime;
     this.mergesdir = region_a.getRegionFileSystem().getMergesDir();
   }
 
   private void transition(RegionMergeTransactionPhase nextPhase) throws IOException {
     transition(nextPhase, false);
   }
 
   private void transition(RegionMergeTransactionPhase nextPhase, boolean isRollback)
       throws IOException {
     if (!isRollback) {
       // Add to the journal first, because if the listener throws an exception
       // we need to roll back starting at 'nextPhase'
       this.journal.add(new JournalEntryImpl(nextPhase));
     }
     for (int i = 0; i < listeners.size(); i++) {
       TransactionListener listener = listeners.get(i);
       if (!isRollback) {
         listener.transition(this, currentPhase, nextPhase);
       } else {
         listener.rollback(this, currentPhase, nextPhase);
       }
     }
     currentPhase = nextPhase;
   }
 
   /**
    * Does checks on merge inputs.
    * @param services
    * @return <code>true</code> if the regions are mergeable else
    *         <code>false</code> if they are not (e.g. its already closed, etc.).
    */
   @Override
   public boolean prepare(final RegionServerServices services) throws IOException {
     if (!region_a.getTableDesc().getTableName()
         .equals(region_b.getTableDesc().getTableName())) {
       LOG.info("Can't merge regions " + region_a + "," + region_b
           + " because they do not belong to the same table");
       return false;
     }
     if (region_a.getRegionInfo().equals(region_b.getRegionInfo())) {
       LOG.info("Can't merge the same region " + region_a);
       return false;
     }
     if (!forcible && !HRegionInfo.areAdjacent(region_a.getRegionInfo(),
             region_b.getRegionInfo())) {
       String msg = "Skip merging " + this.region_a.getRegionInfo().getRegionNameAsString()
           + " and " + this.region_b.getRegionInfo().getRegionNameAsString()
           + ", because they are not adjacent.";
       LOG.info(msg);
       return false;
     }
     if (!this.region_a.isMergeable() || !this.region_b.isMergeable()) {
       return false;
     }
     try {
       boolean regionAHasMergeQualifier = hasMergeQualifierInMeta(services,
           region_a.getRegionInfo().getRegionName());
       if (regionAHasMergeQualifier ||
           hasMergeQualifierInMeta(services, region_b.getRegionInfo().getRegionName())) {
         LOG.debug("Region " + (regionAHasMergeQualifier ?
               region_a.getRegionInfo().getRegionNameAsString() :
                 region_b.getRegionInfo().getRegionNameAsString())
             + " is not mergeable because it has merge qualifier in META");
         return false;
       }
     } catch (IOException e) {
       LOG.warn("Failed judging whether merge transaction is available for "
               + region_a.getRegionInfo().getRegionNameAsString() + " and "
               + region_b.getRegionInfo().getRegionNameAsString(), e);
       return false;
     }
 
     // WARN: make sure there is no parent region of the two merging regions in
     // hbase:meta If exists, fixing up daughters would cause daughter regions(we
     // have merged one) online again when we restart master, so we should clear
     // the parent region to prevent the above case
     // Since HBASE-7721, we don't need fix up daughters any more. so here do
     // nothing
 
     this.mergedRegionInfo = getMergedRegionInfo(region_a.getRegionInfo(),
         region_b.getRegionInfo());
 
     transition(RegionMergeTransactionPhase.PREPARED);
     return true;
   }
 
   /**
    * Run the transaction.
    * @param server Hosting server instance. Can be null when testing
    * @param services Used to online/offline regions.
    * @throws IOException If thrown, transaction failed. Call
    *           {@link #rollback(Server, RegionServerServices)}
    * @return merged region
    * @throws IOException
    * @see #rollback(Server, RegionServerServices)
    */
   @Override
   public HRegion execute(final Server server,
       final RegionServerServices services) throws IOException {
     if (User.isHBaseSecurityEnabled(region_a.getBaseConf())) {
       LOG.warn("Should use execute(Server, RegionServerServices, User)");
     }
     return execute(server, services, null);
   }
 
   @Override
   public HRegion execute(final Server server, final RegionServerServices services, User user)
       throws IOException {
     this.server = server;
     this.rsServices = services;
     useCoordinationForAssignment =
         server == null ? true : ConfigUtil.useZKForAssignment(server.getConfiguration());
     if (rmd == null) {
       rmd = server != null && server.getCoordinatedStateManager() != null ?
           ((BaseCoordinatedStateManager) server.getCoordinatedStateManager())
             .getRegionMergeCoordination().getDefaultDetails()
         : null;
     }
     if (rsCoprocessorHost == null) {
       rsCoprocessorHost = server != null ?
         ((HRegionServer) server).getRegionServerCoprocessorHost() : null;
     }
     final HRegion mergedRegion = createMergedRegion(server, services, user);
     if (rsCoprocessorHost != null) {
       rsCoprocessorHost.postMergeCommit(this.region_a, this.region_b, mergedRegion, user);
     }
     stepsAfterPONR(server, services, mergedRegion, user);
 
     transition(RegionMergeTransactionPhase.COMPLETED);
 
     return mergedRegion;
   }
 
   @Deprecated
   public void stepsAfterPONR(final Server server, final RegionServerServices services,
       final HRegion mergedRegion) throws IOException {
     stepsAfterPONR(server, services, mergedRegion, null);
   }
 
   public void stepsAfterPONR(final Server server, final RegionServerServices services,
       final HRegion mergedRegion, User user) throws IOException {
     openMergedRegion(server, services, mergedRegion);
     if (useCoordination(server)) {
       ((BaseCoordinatedStateManager) server.getCoordinatedStateManager())
         .getRegionMergeCoordination().completeRegionMergeTransaction(services,
           mergedRegionInfo, region_a, region_b, rmd, mergedRegion);
     }
     if (rsCoprocessorHost != null) {
       rsCoprocessorHost.postMerge(region_a, region_b, mergedRegion, user);
     }
   }
 
   /**
    * Prepare the merged region and region files.
    * @param server Hosting server instance. Can be null when testing
    * @param services Used to online/offline regions.
    * @return merged region
    * @throws IOException If thrown, transaction failed. Call
    *           {@link #rollback(Server, RegionServerServices)}
    */
   HRegion createMergedRegion(final Server server,
       final RegionServerServices services, User user) throws IOException {
     LOG.info("Starting merge of " + region_a + " and "
         + region_b.getRegionInfo().getRegionNameAsString() + ", forcible=" + forcible);
     if ((server != null && server.isStopped())
         || (services != null && services.isStopping())) {
       throw new IOException("Server is stopped or stopping");
     }
 
     if (rsCoprocessorHost != null) {
       boolean ret = rsCoprocessorHost.preMerge(region_a, region_b, user);
       if (ret) {
         throw new IOException("Coprocessor bypassing regions " + this.region_a + " "
             + this.region_b + " merge.");
       }
     }
 
     // If true, no cluster to write meta edits to or to use coordination.
     boolean testing = server == null ? true : server.getConfiguration()
         .getBoolean("hbase.testing.nocluster", false);
 
     HRegion mergedRegion = stepsBeforePONR(server, services, testing);
 
     @MetaMutationAnnotation
     final List<Mutation> metaEntries = new ArrayList<Mutation>();
     if (rsCoprocessorHost != null) {
       boolean ret = rsCoprocessorHost.preMergeCommit(region_a, region_b, metaEntries, user);
 
       if (ret) {
         throw new IOException("Coprocessor bypassing regions " + this.region_a + " "
             + this.region_b + " merge.");
       }
       try {
         for (Mutation p : metaEntries) {
           HRegionInfo.parseRegionName(p.getRow());
         }
       } catch (IOException e) {
         LOG.error("Row key of mutation from coprocessor is not parsable as region name."
             + "Mutations from coprocessor should only be for hbase:meta table.", e);
         throw e;
       }
     }
 
     // This is the point of no return. Similar with SplitTransaction.
     // IF we reach the PONR then subsequent failures need to crash out this
     // regionserver
     transition(RegionMergeTransactionPhase.PONR);
 
     // Add merged region and delete region_a and region_b
     // as an atomic update. See HBASE-7721. This update to hbase:meta makes the region
     // will determine whether the region is merged or not in case of failures.
     // If it is successful, master will roll-forward, if not, master will
     // rollback
     if (!testing && useCoordinationForAssignment) {
       if (metaEntries.isEmpty()) {
         MetaTableAccessor.mergeRegions(server.getConnection(),
           mergedRegion.getRegionInfo(), region_a.getRegionInfo(), region_b.getRegionInfo(),
           server.getServerName(), region_a.getTableDesc().getRegionReplication(), masterSystemTime);
       } else {
         mergeRegionsAndPutMetaEntries(server.getConnection(),
           mergedRegion.getRegionInfo(), region_a.getRegionInfo(), region_b.getRegionInfo(),
           server.getServerName(), metaEntries, region_a.getTableDesc().getRegionReplication());
       }
     } else if (services != null && !useCoordinationForAssignment) {
       if (!services.reportRegionStateTransition(TransitionCode.MERGE_PONR,
           mergedRegionInfo, region_a.getRegionInfo(), region_b.getRegionInfo())) {
         // Passed PONR, let SSH clean it up
         throw new IOException("Failed to notify master that merge passed PONR: "
           + region_a.getRegionInfo().getRegionNameAsString() + " and "
           + region_b.getRegionInfo().getRegionNameAsString());
       }
     }
     return mergedRegion;
   }
 
   private void mergeRegionsAndPutMetaEntries(HConnection hConnection,
       HRegionInfo mergedRegion, HRegionInfo regionA, HRegionInfo regionB,
       ServerName serverName, List<Mutation> metaEntries,
       int regionReplication) throws IOException {
     prepareMutationsForMerge(mergedRegion, regionA, regionB, serverName, metaEntries,
       regionReplication);
     MetaTableAccessor.mutateMetaTable(hConnection, metaEntries);
   }
 
   public void prepareMutationsForMerge(HRegionInfo mergedRegion, HRegionInfo regionA,
       HRegionInfo regionB, ServerName serverName, List<Mutation> mutations,
       int regionReplication) throws IOException {
     HRegionInfo copyOfMerged = new HRegionInfo(mergedRegion);
 
     // use the maximum of what master passed us vs local time.
     long time = Math.max(EnvironmentEdgeManager.currentTime(), masterSystemTime);
 
     // Put for parent
     Put putOfMerged = MetaTableAccessor.makePutFromRegionInfo(copyOfMerged, time);
     putOfMerged.add(HConstants.CATALOG_FAMILY, HConstants.MERGEA_QUALIFIER,
       regionA.toByteArray());
     putOfMerged.add(HConstants.CATALOG_FAMILY, HConstants.MERGEB_QUALIFIER,
       regionB.toByteArray());
     mutations.add(putOfMerged);
     // Deletes for merging regions
     Delete deleteA = MetaTableAccessor.makeDeleteFromRegionInfo(regionA, time);
     Delete deleteB = MetaTableAccessor.makeDeleteFromRegionInfo(regionB, time);
     mutations.add(deleteA);
     mutations.add(deleteB);
 
     // Add empty locations for region replicas of the merged region so that number of replicas
     // can be cached whenever the primary region is looked up from meta
     for (int i = 1; i < regionReplication; i++) {
       addEmptyLocation(putOfMerged, i);
     }
 
     // The merged is a new region, openSeqNum = 1 is fine.
     addLocation(putOfMerged, serverName, 1);
   }
 
   public Put addLocation(final Put p, final ServerName sn, long openSeqNum) {
     p.add(HConstants.CATALOG_FAMILY, HConstants.SERVER_QUALIFIER, Bytes
         .toBytes(sn.getHostAndPort()));
     p.add(HConstants.CATALOG_FAMILY, HConstants.STARTCODE_QUALIFIER, Bytes.toBytes(sn
         .getStartcode()));
     p.add(HConstants.CATALOG_FAMILY, HConstants.SEQNUM_QUALIFIER, Bytes.toBytes(openSeqNum));
     return p;
   }
 
   private static Put addEmptyLocation(final Put p, int replicaId) {
     p.addImmutable(HConstants.CATALOG_FAMILY, MetaTableAccessor.getServerColumn(replicaId), null);
     p.addImmutable(HConstants.CATALOG_FAMILY, MetaTableAccessor.getStartCodeColumn(replicaId),
       null);
     p.addImmutable(HConstants.CATALOG_FAMILY, MetaTableAccessor.getSeqNumColumn(replicaId), null);
     return p;
   }
 
   public HRegion stepsBeforePONR(final Server server, final RegionServerServices services,
       boolean testing) throws IOException {
     if (rmd == null) {
       rmd = server != null && server.getCoordinatedStateManager() != null ?
           ((BaseCoordinatedStateManager) server.getCoordinatedStateManager())
             .getRegionMergeCoordination().getDefaultDetails()
         : null;
     }
 
     // If server doesn't have a coordination state manager, don't do coordination actions.
     if (useCoordination(server)) {
       try {
         ((BaseCoordinatedStateManager) server.getCoordinatedStateManager())
             .getRegionMergeCoordination().startRegionMergeTransaction(mergedRegionInfo,
               server.getServerName(), region_a.getRegionInfo(), region_b.getRegionInfo());
       } catch (IOException e) {
         throw new IOException("Failed to start region merge transaction for "
             + this.mergedRegionInfo.getRegionNameAsString(), e);
       }
     } else if (services != null && !useCoordinationForAssignment) {
       if (!services.reportRegionStateTransition(TransitionCode.READY_TO_MERGE,
           mergedRegionInfo, region_a.getRegionInfo(), region_b.getRegionInfo())) {
         throw new IOException("Failed to get ok from master to merge "
           + region_a.getRegionInfo().getRegionNameAsString() + " and "
           + region_b.getRegionInfo().getRegionNameAsString());
       }
     }
     transition(RegionMergeTransactionPhase.SET_MERGING);
     if (useCoordination(server)) {
       // After creating the merge node, wait for master to transition it
       // from PENDING_MERGE to MERGING so that we can move on. We want master
       // knows about it and won't transition any region which is merging.
       ((BaseCoordinatedStateManager) server.getCoordinatedStateManager())
         .getRegionMergeCoordination().waitForRegionMergeTransaction(services,
           mergedRegionInfo, region_a, region_b, rmd);
     }
 
     this.region_a.getRegionFileSystem().createMergesDir();
     transition(RegionMergeTransactionPhase.CREATED_MERGE_DIR);
 
     Map<byte[], List<StoreFile>> hstoreFilesOfRegionA = closeAndOfflineRegion(
         services, this.region_a, true, testing);
     Map<byte[], List<StoreFile>> hstoreFilesOfRegionB = closeAndOfflineRegion(
         services, this.region_b, false, testing);
 
     assert hstoreFilesOfRegionA != null && hstoreFilesOfRegionB != null;
 
 
     //
     // mergeStoreFiles creates merged region dirs under the region_a merges dir
     // Nothing to unroll here if failure -- clean up of CREATE_MERGE_DIR will
     // clean this up.
     mergeStoreFiles(hstoreFilesOfRegionA, hstoreFilesOfRegionB);
 
     if (useCoordination(server)) {
       try {
         // Do the final check in case any merging region is moved somehow. If so, the transition
         // will fail.
         ((BaseCoordinatedStateManager) server.getCoordinatedStateManager())
             .getRegionMergeCoordination().confirmRegionMergeTransaction(this.mergedRegionInfo,
               region_a.getRegionInfo(), region_b.getRegionInfo(), server.getServerName(), rmd);
       } catch (IOException e) {
         throw new IOException("Failed setting MERGING on "
             + this.mergedRegionInfo.getRegionNameAsString(), e);
       }
     }
 
     // Log to the journal that we are creating merged region. We could fail
     // halfway through. If we do, we could have left
     // stuff in fs that needs cleanup -- a storefile or two. Thats why we
     // add entry to journal BEFORE rather than AFTER the change.
     transition(RegionMergeTransactionPhase.STARTED_MERGED_REGION_CREATION);
     HRegion mergedRegion = createMergedRegionFromMerges(this.region_a,
         this.region_b, this.mergedRegionInfo);
     return mergedRegion;
   }
 
   /**
    * Create a merged region from the merges directory under region a. In order
    * to mock it for tests, place it with a new method.
    * @param a hri of region a
    * @param b hri of region b
    * @param mergedRegion hri of merged region
    * @return merged HRegion.
    * @throws IOException
    */
   HRegion createMergedRegionFromMerges(final HRegion a, final HRegion b,
       final HRegionInfo mergedRegion) throws IOException {
     return a.createMergedRegionFromMerges(mergedRegion, b);
   }
 
   /**
    * Close the merging region and offline it in regionserver
    * @param services
    * @param region
    * @param isRegionA true if it is merging region a, false if it is region b
    * @param testing true if it is testing
    * @return a map of family name to list of store files
    * @throws IOException
    */
   private Map<byte[], List<StoreFile>> closeAndOfflineRegion(
       final RegionServerServices services, final HRegion region,
       final boolean isRegionA, final boolean testing) throws IOException {
     Map<byte[], List<StoreFile>> hstoreFilesToMerge = null;
     Exception exceptionToThrow = null;
     try {
       hstoreFilesToMerge = region.close(false);
     } catch (Exception e) {
       exceptionToThrow = e;
     }
     if (exceptionToThrow == null && hstoreFilesToMerge == null) {
       // The region was closed by a concurrent thread. We can't continue
       // with the merge, instead we must just abandon the merge. If we
       // reopen or merge this could cause problems because the region has
       // probably already been moved to a different server, or is in the
       // process of moving to a different server.
       exceptionToThrow = closedByOtherException;
     }
     if (exceptionToThrow != closedByOtherException) {
       transition(isRegionA ? RegionMergeTransactionPhase.CLOSED_REGION_A
           : RegionMergeTransactionPhase.CLOSED_REGION_B);
     }
     if (exceptionToThrow != null) {
       if (exceptionToThrow instanceof IOException)
         throw (IOException) exceptionToThrow;
       throw new IOException(exceptionToThrow);
     }
 
     if (!testing) {
       services.removeFromOnlineRegions(region, null);
     }
     transition(isRegionA ? RegionMergeTransactionPhase.OFFLINED_REGION_A
         : RegionMergeTransactionPhase.OFFLINED_REGION_B);
     return hstoreFilesToMerge;
   }
 
   /**
    * Get merged region info through the specified two regions
    * @param a merging region A
    * @param b merging region B
    * @return the merged region info
    */
   public static HRegionInfo getMergedRegionInfo(final HRegionInfo a,
       final HRegionInfo b) {
     long rid = EnvironmentEdgeManager.currentTime();
     // Regionid is timestamp. Merged region's id can't be less than that of
     // merging regions else will insert at wrong location in hbase:meta
     if (rid < a.getRegionId() || rid < b.getRegionId()) {
       LOG.warn("Clock skew; merging regions id are " + a.getRegionId()
           + " and " + b.getRegionId() + ", but current time here is " + rid);
       rid = Math.max(a.getRegionId(), b.getRegionId()) + 1;
     }
 
     byte[] startKey = null;
     byte[] endKey = null;
     // Choose the smaller as start key
     if (a.compareTo(b) <= 0) {
       startKey = a.getStartKey();
     } else {
       startKey = b.getStartKey();
     }
     // Choose the bigger as end key
     if (Bytes.equals(a.getEndKey(), HConstants.EMPTY_BYTE_ARRAY)
         || (!Bytes.equals(b.getEndKey(), HConstants.EMPTY_BYTE_ARRAY)
             && Bytes.compareTo(a.getEndKey(), b.getEndKey()) > 0)) {
       endKey = a.getEndKey();
     } else {
       endKey = b.getEndKey();
     }
 
     // Merged region is sorted between two merging regions in META
     HRegionInfo mergedRegionInfo = new HRegionInfo(a.getTable(), startKey,
         endKey, false, rid);
     return mergedRegionInfo;
   }
 
   /**
    * Perform time consuming opening of the merged region.
    * @param server Hosting server instance. Can be null when testing
    * @param services Used to online/offline regions.
    * @param merged the merged region
    * @throws IOException If thrown, transaction failed. Call
    *           {@link #rollback(Server, RegionServerServices)}
    */
   void openMergedRegion(final Server server,
       final RegionServerServices services, HRegion merged) throws IOException {
     boolean stopped = server != null && server.isStopped();
     boolean stopping = services != null && services.isStopping();
     if (stopped || stopping) {
       LOG.info("Not opening merged region  " + merged.getRegionInfo().getRegionNameAsString()
           + " because stopping=" + stopping + ", stopped=" + stopped);
       return;
     }
     HRegionInfo hri = merged.getRegionInfo();
     LoggingProgressable reporter = server == null ? null
         : new LoggingProgressable(hri, server.getConfiguration().getLong(
             "hbase.regionserver.regionmerge.open.log.interval", 10000));
     merged.openHRegion(reporter);
 
     if (services != null) {
       try {
         if (useCoordinationForAssignment) {
           services.postOpenDeployTasks(merged);
         } else if (!services.reportRegionStateTransition(TransitionCode.MERGED,
             mergedRegionInfo, region_a.getRegionInfo(), region_b.getRegionInfo())) {
           throw new IOException("Failed to report merged region to master: "
             + mergedRegionInfo.getShortNameToLog());
         }
         services.addToOnlineRegions(merged);
       } catch (KeeperException ke) {
         throw new IOException(ke);
       }
     }
 
   }
 
   /**
    * Create reference file(s) of merging regions under the region_a merges dir
    * @param hstoreFilesOfRegionA
    * @param hstoreFilesOfRegionB
    * @throws IOException
    */
   private void mergeStoreFiles(
       Map<byte[], List<StoreFile>> hstoreFilesOfRegionA,
       Map<byte[], List<StoreFile>> hstoreFilesOfRegionB)
       throws IOException {
     // Create reference file(s) of region A in mergdir
     HRegionFileSystem fs_a = this.region_a.getRegionFileSystem();
     for (Map.Entry<byte[], List<StoreFile>> entry : hstoreFilesOfRegionA
         .entrySet()) {
       String familyName = Bytes.toString(entry.getKey());
       for (StoreFile storeFile : entry.getValue()) {
         fs_a.mergeStoreFile(this.mergedRegionInfo, familyName, storeFile,
             this.mergesdir);
       }
     }
     // Create reference file(s) of region B in mergedir
     HRegionFileSystem fs_b = this.region_b.getRegionFileSystem();
     for (Map.Entry<byte[], List<StoreFile>> entry : hstoreFilesOfRegionB
         .entrySet()) {
       String familyName = Bytes.toString(entry.getKey());
       for (StoreFile storeFile : entry.getValue()) {
         fs_b.mergeStoreFile(this.mergedRegionInfo, familyName, storeFile,
             this.mergesdir);
       }
     }
   }
 
   /**
    * @param server Hosting server instance (May be null when testing).
    * @param services Services of regionserver, used to online regions.
    * @throws IOException If thrown, rollback failed. Take drastic action.
    * @return True if we successfully rolled back, false if we got to the point
    *         of no return and so now need to abort the server to minimize
    *         damage.
    */
   @Override
   @SuppressWarnings("deprecation")
   public boolean rollback(final Server server,
       final RegionServerServices services) throws IOException {
     if (User.isHBaseSecurityEnabled(region_a.getBaseConf())) {
       LOG.warn("Should use execute(Server, RegionServerServices, User)");
     }
     return rollback(server, services, null);
   }
 
   @Override
   public boolean rollback(final Server server,
       final RegionServerServices services, User user) throws IOException {
     assert this.mergedRegionInfo != null;
     // Coprocessor callback
     if (rsCoprocessorHost != null) {
       rsCoprocessorHost.preRollBackMerge(region_a, region_b, user);
     }
 
     boolean result = true;
     ListIterator<JournalEntry> iterator = this.journal
         .listIterator(this.journal.size());
     // Iterate in reverse.
     while (iterator.hasPrevious()) {
       JournalEntry je = iterator.previous();
 
       transition(je.getPhase(), true);
 
       switch (je.getPhase()) {
 
         case SET_MERGING:
         if (useCoordination(server)) {
           ((BaseCoordinatedStateManager) server.getCoordinatedStateManager())
               .getRegionMergeCoordination().clean(this.mergedRegionInfo);
           } else if (services != null && !useCoordinationForAssignment
               && !services.reportRegionStateTransition(TransitionCode.MERGE_REVERTED,
                   mergedRegionInfo, region_a.getRegionInfo(), region_b.getRegionInfo())) {
             return false;
         }
           break;
 
         case CREATED_MERGE_DIR:
           this.region_a.writestate.writesEnabled = true;
           this.region_b.writestate.writesEnabled = true;
           this.region_a.getRegionFileSystem().cleanupMergesDir();
           break;
 
         case CLOSED_REGION_A:
           try {
             // So, this returns a seqid but if we just closed and then reopened,
             // we should be ok. On close, we flushed using sequenceid obtained
             // from hosting regionserver so no need to propagate the sequenceid
             // returned out of initialize below up into regionserver as we
             // normally do.
             this.region_a.initialize();
           } catch (IOException e) {
             LOG.error("Failed rollbacking CLOSED_REGION_A of region "
                 + this.region_a.getRegionInfo().getRegionNameAsString(), e);
             throw new RuntimeException(e);
           }
           break;
 
         case OFFLINED_REGION_A:
           if (services != null)
             services.addToOnlineRegions(this.region_a);
           break;
 
         case CLOSED_REGION_B:
           try {
             this.region_b.initialize();
           } catch (IOException e) {
             LOG.error("Failed rollbacking CLOSED_REGION_A of region "
                 + this.region_b.getRegionInfo().getRegionNameAsString(), e);
             throw new RuntimeException(e);
           }
           break;
 
         case OFFLINED_REGION_B:
           if (services != null)
             services.addToOnlineRegions(this.region_b);
           break;
 
         case STARTED_MERGED_REGION_CREATION:
           this.region_a.getRegionFileSystem().cleanupMergedRegion(
               this.mergedRegionInfo);
           break;
 
         case PONR:
           // We got to the point-of-no-return so we need to just abort. Return
           // immediately. Do not clean up created merged regions.
           return false;
 
         // Informational only cases
         case STARTED:
         case PREPARED:
         case COMPLETED:
           break;
 
         default:
           throw new RuntimeException("Unhandled journal entry: " + je);
       }
     }
     // Coprocessor callback
     if (rsCoprocessorHost != null) {
       rsCoprocessorHost.postRollBackMerge(region_a, region_b, user);
     }
 
     return result;
   }
 
   @Override
   public HRegionInfo getMergedRegionInfo() {
     return this.mergedRegionInfo;
   }
 
   // For unit testing.
   Path getMergesDir() {
     return this.mergesdir;
   }
 
   private boolean useCoordination(final Server server) {
     return server != null && useCoordinationForAssignment
         && server.getCoordinatedStateManager() != null;
   }
 
 
 
   /**
    * Checks if the given region has merge qualifier in hbase:meta
    * @param services
    * @param regionName name of specified region
    * @return true if the given region has merge qualifier in META.(It will be
    *         cleaned by CatalogJanitor)
    * @throws IOException
    */
   boolean hasMergeQualifierInMeta(final RegionServerServices services,
       final byte[] regionName) throws IOException {
     if (services == null) return false;
     // Get merge regions if it is a merged region and already has merge
     // qualifier
     Pair<HRegionInfo, HRegionInfo> mergeRegions = MetaTableAccessor
         .getRegionsFromMergeQualifier(services.getConnection(), regionName);
     if (mergeRegions != null &&
         (mergeRegions.getFirst() != null || mergeRegions.getSecond() != null)) {
       // It has merge qualifier
       return true;
     }
     return false;
   }
 
   @Override
   public List<JournalEntry> getJournal() {
     return journal;
   }
 
   @Override
   public RegionMergeTransaction registerTransactionListener(TransactionListener listener) {
     listeners.add(listener);
     return this;
   }
 
   @Override
   public Server getServer() {
     return server;
   }
 
   @Override
   public RegionServerServices getRegionServerServices() {
     return rsServices;
   }
 
   @Override
   public String toString() {
     StringBuilder sb = new StringBuilder();
     for (int i = 0; i < journal.size(); i++) {
       JournalEntry je = journal.get(i);
       sb.append(je.toString());
       if (i != 0) {
         JournalEntry jep = journal.get(i-1);
         long delta = je.getTimeStamp() - jep.getTimeStamp();
         if (delta != 0) {
           sb.append(" (+" + delta + " ms)");
         }
       }
       sb.append("\n");
     }
     return sb.toString();
   }
 }