/**
 *
 * 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;

import java.io.IOException;
import java.io.InterruptedIOException;
import java.net.InetSocketAddress;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.NavigableSet;
import java.util.Optional;
import java.util.OptionalDouble;
import java.util.OptionalLong;
import java.util.Set;
import java.util.concurrent.Callable;
import java.util.concurrent.CompletionService;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorCompletionService;
import java.util.concurrent.Future;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.atomic.AtomicLong;
import java.util.concurrent.locks.ReentrantLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;
import java.util.function.Predicate;
import java.util.function.ToLongFunction;
import java.util.stream.Collectors;
import java.util.stream.LongStream;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.hbase.Cell;
import org.apache.hadoop.hbase.CellComparator;
import org.apache.hadoop.hbase.CellUtil;
import org.apache.hadoop.hbase.CompoundConfiguration;
import org.apache.hadoop.hbase.HConstants;
import org.apache.hadoop.hbase.MemoryCompactionPolicy;
import org.apache.hadoop.hbase.TableName;
import org.apache.hadoop.hbase.backup.FailedArchiveException;
import org.apache.hadoop.hbase.client.ColumnFamilyDescriptor;
import org.apache.hadoop.hbase.client.RegionInfo;
import org.apache.hadoop.hbase.client.Scan;
import org.apache.hadoop.hbase.conf.ConfigurationManager;
import org.apache.hadoop.hbase.conf.PropagatingConfigurationObserver;
import org.apache.hadoop.hbase.io.HeapSize;
import org.apache.hadoop.hbase.io.compress.Compression;
import org.apache.hadoop.hbase.io.crypto.Encryption;
import org.apache.hadoop.hbase.io.hfile.CacheConfig;
import org.apache.hadoop.hbase.io.hfile.HFile;
import org.apache.hadoop.hbase.io.hfile.HFileContext;
import org.apache.hadoop.hbase.io.hfile.HFileContextBuilder;
import org.apache.hadoop.hbase.io.hfile.HFileDataBlockEncoder;
import org.apache.hadoop.hbase.io.hfile.HFileDataBlockEncoderImpl;
import org.apache.hadoop.hbase.io.hfile.HFileScanner;
import org.apache.hadoop.hbase.io.hfile.InvalidHFileException;
import org.apache.hadoop.hbase.log.HBaseMarkers;
import org.apache.hadoop.hbase.monitoring.MonitoredTask;
import org.apache.hadoop.hbase.regionserver.compactions.CompactionContext;
import org.apache.hadoop.hbase.regionserver.compactions.CompactionLifeCycleTracker;
import org.apache.hadoop.hbase.regionserver.compactions.CompactionProgress;
import org.apache.hadoop.hbase.regionserver.compactions.CompactionRequestImpl;
import org.apache.hadoop.hbase.regionserver.compactions.DefaultCompactor;
import org.apache.hadoop.hbase.regionserver.compactions.OffPeakHours;
import org.apache.hadoop.hbase.regionserver.querymatcher.ScanQueryMatcher;
import org.apache.hadoop.hbase.regionserver.throttle.ThroughputController;
import org.apache.hadoop.hbase.regionserver.wal.WALUtil;
import org.apache.hadoop.hbase.security.EncryptionUtil;
import org.apache.hadoop.hbase.security.User;
import org.apache.hadoop.hbase.util.Bytes;
import org.apache.hadoop.hbase.util.ChecksumType;
import org.apache.hadoop.hbase.util.ClassSize;
import org.apache.hadoop.hbase.util.EnvironmentEdgeManager;
import org.apache.hadoop.hbase.util.Pair;
import org.apache.hadoop.hbase.util.ReflectionUtils;
import org.apache.hadoop.util.StringUtils;
import org.apache.hadoop.util.StringUtils.TraditionalBinaryPrefix;
import org.apache.yetus.audience.InterfaceAudience;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.apache.hbase.thirdparty.com.google.common.annotations.VisibleForTesting;
import org.apache.hbase.thirdparty.com.google.common.base.Preconditions;
import org.apache.hbase.thirdparty.com.google.common.collect.ImmutableCollection;
import org.apache.hbase.thirdparty.com.google.common.collect.ImmutableList;
import org.apache.hbase.thirdparty.com.google.common.collect.Lists;
import org.apache.hbase.thirdparty.com.google.common.collect.Sets;
import org.apache.hbase.thirdparty.org.apache.commons.collections4.CollectionUtils;
import org.apache.hbase.thirdparty.org.apache.commons.collections4.IterableUtils;
import org.apache.hadoop.hbase.shaded.protobuf.ProtobufUtil;
import org.apache.hadoop.hbase.shaded.protobuf.generated.WALProtos.CompactionDescriptor;

/**
 * A Store holds a column family in a Region.  Its a memstore and a set of zero
 * or more StoreFiles, which stretch backwards over time.
 *
 * <p>There's no reason to consider append-logging at this level; all logging
 * and locking is handled at the HRegion level.  Store just provides
 * services to manage sets of StoreFiles.  One of the most important of those
 * services is compaction services where files are aggregated once they pass
 * a configurable threshold.
 *
 * <p>Locking and transactions are handled at a higher level.  This API should
 * not be called directly but by an HRegion manager.
 */
@InterfaceAudience.Private
public class HStore implements Store, HeapSize, StoreConfigInformation, PropagatingConfigurationObserver {
  public static final String MEMSTORE_CLASS_NAME = "hbase.regionserver.memstore.class";
  public static final String COMPACTCHECKER_INTERVAL_MULTIPLIER_KEY =
      "hbase.server.compactchecker.interval.multiplier";
  public static final String BLOCKING_STOREFILES_KEY = "hbase.hstore.blockingStoreFiles";
  public static final String BLOCK_STORAGE_POLICY_KEY = "hbase.hstore.block.storage.policy";
  // keep in accordance with HDFS default storage policy
  public static final String DEFAULT_BLOCK_STORAGE_POLICY = "HOT";
  public static final int DEFAULT_COMPACTCHECKER_INTERVAL_MULTIPLIER = 1000;
  public static final int DEFAULT_BLOCKING_STOREFILE_COUNT = 16;

  private static final Logger LOG = LoggerFactory.getLogger(HStore.class);

  protected final MemStore memstore;
  // This stores directory in the filesystem.
  protected final HRegion region;
  private final ColumnFamilyDescriptor family;
  private final HRegionFileSystem fs;
  protected Configuration conf;
  protected CacheConfig cacheConf;
  private long lastCompactSize = 0;
  volatile boolean forceMajor = false;
  /* how many bytes to write between status checks */
  static int closeCheckInterval = 0;
  private AtomicLong storeSize = new AtomicLong();
  private AtomicLong totalUncompressedBytes = new AtomicLong();

  /**
   * RWLock for store operations.
   * Locked in shared mode when the list of component stores is looked at:
   *   - all reads/writes to table data
   *   - checking for split
   * Locked in exclusive mode when the list of component stores is modified:
   *   - closing
   *   - completing a compaction
   */
  final ReentrantReadWriteLock lock = new ReentrantReadWriteLock();
  /**
   * Lock specific to archiving compacted store files.  This avoids races around
   * the combination of retrieving the list of compacted files and moving them to
   * the archive directory.  Since this is usually a background process (other than
   * on close), we don't want to handle this with the store write lock, which would
   * block readers and degrade performance.
   *
   * Locked by:
   *   - CompactedHFilesDispatchHandler via closeAndArchiveCompactedFiles()
   *   - close()
   */
  final ReentrantLock archiveLock = new ReentrantLock();

  private final boolean verifyBulkLoads;

  private ScanInfo scanInfo;

  // All access must be synchronized.
  // TODO: ideally, this should be part of storeFileManager, as we keep passing this to it.
  private final List<HStoreFile> filesCompacting = Lists.newArrayList();

  // All access must be synchronized.
  private final Set<ChangedReadersObserver> changedReaderObservers =
    Collections.newSetFromMap(new ConcurrentHashMap<ChangedReadersObserver, Boolean>());

  protected final int blocksize;
  private HFileDataBlockEncoder dataBlockEncoder;

  /** Checksum configuration */
  protected ChecksumType checksumType;
  protected int bytesPerChecksum;

  // Comparing KeyValues
  protected final CellComparator comparator;

  final StoreEngine<?, ?, ?, ?> storeEngine;

  private static final AtomicBoolean offPeakCompactionTracker = new AtomicBoolean();
  private volatile OffPeakHours offPeakHours;

  private static final int DEFAULT_FLUSH_RETRIES_NUMBER = 10;
  private int flushRetriesNumber;
  private int pauseTime;

  private long blockingFileCount;
  private int compactionCheckMultiplier;
  protected Encryption.Context cryptoContext = Encryption.Context.NONE;

  private AtomicLong flushedCellsCount = new AtomicLong();
  private AtomicLong compactedCellsCount = new AtomicLong();
  private AtomicLong majorCompactedCellsCount = new AtomicLong();
  private AtomicLong flushedCellsSize = new AtomicLong();
  private AtomicLong flushedOutputFileSize = new AtomicLong();
  private AtomicLong compactedCellsSize = new AtomicLong();
  private AtomicLong majorCompactedCellsSize = new AtomicLong();

  /**
   * Constructor
   * @param region
   * @param family HColumnDescriptor for this column
   * @param confParam configuration object
   * failed.  Can be null.
   * @throws IOException
   */
  protected HStore(final HRegion region, final ColumnFamilyDescriptor family,
      final Configuration confParam) throws IOException {

    this.fs = region.getRegionFileSystem();

    // Assemble the store's home directory and Ensure it exists.
    fs.createStoreDir(family.getNameAsString());
    this.region = region;
    this.family = family;
    // 'conf' renamed to 'confParam' b/c we use this.conf in the constructor
    // CompoundConfiguration will look for keys in reverse order of addition, so we'd
    // add global config first, then table and cf overrides, then cf metadata.
    this.conf = new CompoundConfiguration()
      .add(confParam)
      .addBytesMap(region.getTableDescriptor().getValues())
      .addStringMap(family.getConfiguration())
      .addBytesMap(family.getValues());
    this.blocksize = family.getBlocksize();

    // set block storage policy for store directory
    String policyName = family.getStoragePolicy();
    if (null == policyName) {
      policyName = this.conf.get(BLOCK_STORAGE_POLICY_KEY, DEFAULT_BLOCK_STORAGE_POLICY);
    }
    this.fs.setStoragePolicy(family.getNameAsString(), policyName.trim());

    this.dataBlockEncoder = new HFileDataBlockEncoderImpl(family.getDataBlockEncoding());

    this.comparator = region.getCellComparator();
    // used by ScanQueryMatcher
    long timeToPurgeDeletes =
        Math.max(conf.getLong("hbase.hstore.time.to.purge.deletes", 0), 0);
    LOG.trace("Time to purge deletes set to {}ms in store {}", timeToPurgeDeletes, this);
    // Get TTL
    long ttl = determineTTLFromFamily(family);
    // Why not just pass a HColumnDescriptor in here altogether?  Even if have
    // to clone it?
    scanInfo = new ScanInfo(conf, family, ttl, timeToPurgeDeletes, this.comparator);
    this.memstore = getMemstore();
    this.offPeakHours = OffPeakHours.getInstance(conf);

    // Setting up cache configuration for this family
    createCacheConf(family);

    this.verifyBulkLoads = conf.getBoolean("hbase.hstore.bulkload.verify", false);

    this.blockingFileCount =
        conf.getInt(BLOCKING_STOREFILES_KEY, DEFAULT_BLOCKING_STOREFILE_COUNT);
    this.compactionCheckMultiplier = conf.getInt(
        COMPACTCHECKER_INTERVAL_MULTIPLIER_KEY, DEFAULT_COMPACTCHECKER_INTERVAL_MULTIPLIER);
    if (this.compactionCheckMultiplier <= 0) {
      LOG.error("Compaction check period multiplier must be positive, setting default: {}",
          DEFAULT_COMPACTCHECKER_INTERVAL_MULTIPLIER);
      this.compactionCheckMultiplier = DEFAULT_COMPACTCHECKER_INTERVAL_MULTIPLIER;
    }

    if (HStore.closeCheckInterval == 0) {
      HStore.closeCheckInterval = conf.getInt(
          "hbase.hstore.close.check.interval", 10*1000*1000 /* 10 MB */);
    }

    this.storeEngine = createStoreEngine(this, this.conf, this.comparator);
    this.storeEngine.getStoreFileManager().loadFiles(loadStoreFiles());

    // Initialize checksum type from name. The names are CRC32, CRC32C, etc.
    this.checksumType = getChecksumType(conf);
    // Initialize bytes per checksum
    this.bytesPerChecksum = getBytesPerChecksum(conf);
    flushRetriesNumber = conf.getInt(
        "hbase.hstore.flush.retries.number", DEFAULT_FLUSH_RETRIES_NUMBER);
    pauseTime = conf.getInt(HConstants.HBASE_SERVER_PAUSE, HConstants.DEFAULT_HBASE_SERVER_PAUSE);
    if (flushRetriesNumber <= 0) {
      throw new IllegalArgumentException(
          "hbase.hstore.flush.retries.number must be > 0, not "
              + flushRetriesNumber);
    }
    cryptoContext = EncryptionUtil.createEncryptionContext(conf, family);

    LOG.info("Store={},  memstore type={}, storagePolicy={}, verifyBulkLoads={}",
        getColumnFamilyName(), this.memstore.getClass().getSimpleName(), policyName,
        this.verifyBulkLoads);
  }

  /**
   * @return MemStore Instance to use in this store.
   */
  private MemStore getMemstore() {
    MemStore ms = null;
    // Check if in-memory-compaction configured. Note MemoryCompactionPolicy is an enum!
    MemoryCompactionPolicy inMemoryCompaction = null;
    if (this.getTableName().isSystemTable()) {
      inMemoryCompaction = MemoryCompactionPolicy.valueOf(
          conf.get("hbase.systemtables.compacting.memstore.type", "NONE"));
    } else {
      inMemoryCompaction = family.getInMemoryCompaction();
    }
    if (inMemoryCompaction == null) {
      inMemoryCompaction =
          MemoryCompactionPolicy.valueOf(conf.get(CompactingMemStore.COMPACTING_MEMSTORE_TYPE_KEY,
              CompactingMemStore.COMPACTING_MEMSTORE_TYPE_DEFAULT));
    }
    switch (inMemoryCompaction) {
      case NONE:
        ms = ReflectionUtils.newInstance(DefaultMemStore.class,
            new Object[] { conf, this.comparator,
                this.getHRegion().getRegionServicesForStores()});
        break;
      default:
        Class<? extends CompactingMemStore> clz = conf.getClass(MEMSTORE_CLASS_NAME,
            CompactingMemStore.class, CompactingMemStore.class);
        ms = ReflectionUtils.newInstance(clz, new Object[]{conf, this.comparator, this,
            this.getHRegion().getRegionServicesForStores(), inMemoryCompaction});
    }
    return ms;
  }

  /**
   * Creates the cache config.
   * @param family The current column family.
   */
  protected void createCacheConf(final ColumnFamilyDescriptor family) {
    this.cacheConf = new CacheConfig(conf, family);
  }

  /**
   * Creates the store engine configured for the given Store.
   * @param store The store. An unfortunate dependency needed due to it
   *              being passed to coprocessors via the compactor.
   * @param conf Store configuration.
   * @param kvComparator KVComparator for storeFileManager.
   * @return StoreEngine to use.
   */
  protected StoreEngine<?, ?, ?, ?> createStoreEngine(HStore store, Configuration conf,
      CellComparator kvComparator) throws IOException {
    return StoreEngine.create(store, conf, comparator);
  }

  /**
   * @param family
   * @return TTL in seconds of the specified family
   */
  public static long determineTTLFromFamily(final ColumnFamilyDescriptor family) {
    // HCD.getTimeToLive returns ttl in seconds.  Convert to milliseconds.
    long ttl = family.getTimeToLive();
    if (ttl == HConstants.FOREVER) {
      // Default is unlimited ttl.
      ttl = Long.MAX_VALUE;
    } else if (ttl == -1) {
      ttl = Long.MAX_VALUE;
    } else {
      // Second -> ms adjust for user data
      ttl *= 1000;
    }
    return ttl;
  }

  @Override
  public String getColumnFamilyName() {
    return this.family.getNameAsString();
  }

  @Override
  public TableName getTableName() {
    return this.getRegionInfo().getTable();
  }

  @Override
  public FileSystem getFileSystem() {
    return this.fs.getFileSystem();
  }

  public HRegionFileSystem getRegionFileSystem() {
    return this.fs;
  }

  /* Implementation of StoreConfigInformation */
  @Override
  public long getStoreFileTtl() {
    // TTL only applies if there's no MIN_VERSIONs setting on the column.
    return (this.scanInfo.getMinVersions() == 0) ? this.scanInfo.getTtl() : Long.MAX_VALUE;
  }

  @Override
  public long getMemStoreFlushSize() {
    // TODO: Why is this in here?  The flushsize of the region rather than the store?  St.Ack
    return this.region.memstoreFlushSize;
  }

  @Override
  public MemStoreSize getFlushableSize() {
    return this.memstore.getFlushableSize();
  }

  @Override
  public MemStoreSize getSnapshotSize() {
    return this.memstore.getSnapshotSize();
  }

  @Override
  public long getCompactionCheckMultiplier() {
    return this.compactionCheckMultiplier;
  }

  @Override
  public long getBlockingFileCount() {
    return blockingFileCount;
  }
  /* End implementation of StoreConfigInformation */

  /**
   * Returns the configured bytesPerChecksum value.
   * @param conf The configuration
   * @return The bytesPerChecksum that is set in the configuration
   */
  public static int getBytesPerChecksum(Configuration conf) {
    return conf.getInt(HConstants.BYTES_PER_CHECKSUM,
                       HFile.DEFAULT_BYTES_PER_CHECKSUM);
  }

  /**
   * Returns the configured checksum algorithm.
   * @param conf The configuration
   * @return The checksum algorithm that is set in the configuration
   */
  public static ChecksumType getChecksumType(Configuration conf) {
    String checksumName = conf.get(HConstants.CHECKSUM_TYPE_NAME);
    if (checksumName == null) {
      return ChecksumType.getDefaultChecksumType();
    } else {
      return ChecksumType.nameToType(checksumName);
    }
  }

  /**
   * @return how many bytes to write between status checks
   */
  public static int getCloseCheckInterval() {
    return closeCheckInterval;
  }

  @Override
  public ColumnFamilyDescriptor getColumnFamilyDescriptor() {
    return this.family;
  }

  @Override
  public OptionalLong getMaxSequenceId() {
    return StoreUtils.getMaxSequenceIdInList(this.getStorefiles());
  }

  @Override
  public OptionalLong getMaxMemStoreTS() {
    return StoreUtils.getMaxMemStoreTSInList(this.getStorefiles());
  }

  /**
   * @param tabledir {@link Path} to where the table is being stored
   * @param hri {@link RegionInfo} for the region.
   * @param family {@link ColumnFamilyDescriptor} describing the column family
   * @return Path to family/Store home directory.
   */
  @Deprecated
  public static Path getStoreHomedir(final Path tabledir,
      final RegionInfo hri, final byte[] family) {
    return getStoreHomedir(tabledir, hri.getEncodedName(), family);
  }

  /**
   * @param tabledir {@link Path} to where the table is being stored
   * @param encodedName Encoded region name.
   * @param family {@link ColumnFamilyDescriptor} describing the column family
   * @return Path to family/Store home directory.
   */
  @Deprecated
  public static Path getStoreHomedir(final Path tabledir,
      final String encodedName, final byte[] family) {
    return new Path(tabledir, new Path(encodedName, Bytes.toString(family)));
  }

  /**
   * @return the data block encoder
   */
  public HFileDataBlockEncoder getDataBlockEncoder() {
    return dataBlockEncoder;
  }

  /**
   * Should be used only in tests.
   * @param blockEncoder the block delta encoder to use
   */
  void setDataBlockEncoderInTest(HFileDataBlockEncoder blockEncoder) {
    this.dataBlockEncoder = blockEncoder;
  }

  /**
   * Creates an unsorted list of StoreFile loaded in parallel
   * from the given directory.
   * @throws IOException
   */
  private List<HStoreFile> loadStoreFiles() throws IOException {
    Collection<StoreFileInfo> files = fs.getStoreFiles(getColumnFamilyName());
    return openStoreFiles(files);
  }

  private List<HStoreFile> openStoreFiles(Collection<StoreFileInfo> files) throws IOException {
    if (CollectionUtils.isEmpty(files)) {
      return Collections.emptyList();
    }
    // initialize the thread pool for opening store files in parallel..
    ThreadPoolExecutor storeFileOpenerThreadPool =
      this.region.getStoreFileOpenAndCloseThreadPool("StoreFileOpenerThread-" +
          this.getColumnFamilyName());
    CompletionService<HStoreFile> completionService = new ExecutorCompletionService<>(storeFileOpenerThreadPool);

    int totalValidStoreFile = 0;
    for (StoreFileInfo storeFileInfo : files) {
      // open each store file in parallel
      completionService.submit(() -> this.createStoreFileAndReader(storeFileInfo));
      totalValidStoreFile++;
    }

    ArrayList<HStoreFile> results = new ArrayList<>(files.size());
    IOException ioe = null;
    try {
      for (int i = 0; i < totalValidStoreFile; i++) {
        try {
          HStoreFile storeFile = completionService.take().get();
          if (storeFile != null) {
            long length = storeFile.getReader().length();
            this.storeSize.addAndGet(length);
            this.totalUncompressedBytes
                .addAndGet(storeFile.getReader().getTotalUncompressedBytes());
            LOG.debug("loaded {}", storeFile);
            results.add(storeFile);
          }
        } catch (InterruptedException e) {
          if (ioe == null) ioe = new InterruptedIOException(e.getMessage());
        } catch (ExecutionException e) {
          if (ioe == null) ioe = new IOException(e.getCause());
        }
      }
    } finally {
      storeFileOpenerThreadPool.shutdownNow();
    }
    if (ioe != null) {
      // close StoreFile readers
      boolean evictOnClose =
          cacheConf != null? cacheConf.shouldEvictOnClose(): true;
      for (HStoreFile file : results) {
        try {
          if (file != null) {
            file.closeStoreFile(evictOnClose);
          }
        } catch (IOException e) {
          LOG.warn("Could not close store file", e);
        }
      }
      throw ioe;
    }

    return results;
  }

  @Override
  public void refreshStoreFiles() throws IOException {
    Collection<StoreFileInfo> newFiles = fs.getStoreFiles(getColumnFamilyName());
    refreshStoreFilesInternal(newFiles);
  }

  /**
   * Replaces the store files that the store has with the given files. Mainly used by secondary
   * region replicas to keep up to date with the primary region files.
   * @throws IOException
   */
  public void refreshStoreFiles(Collection<String> newFiles) throws IOException {
    List<StoreFileInfo> storeFiles = new ArrayList<>(newFiles.size());
    for (String file : newFiles) {
      storeFiles.add(fs.getStoreFileInfo(getColumnFamilyName(), file));
    }
    refreshStoreFilesInternal(storeFiles);
  }

  /**
   * Checks the underlying store files, and opens the files that  have not
   * been opened, and removes the store file readers for store files no longer
   * available. Mainly used by secondary region replicas to keep up to date with
   * the primary region files.
   * @throws IOException
   */
  private void refreshStoreFilesInternal(Collection<StoreFileInfo> newFiles) throws IOException {
    StoreFileManager sfm = storeEngine.getStoreFileManager();
    Collection<HStoreFile> currentFiles = sfm.getStorefiles();
    Collection<HStoreFile> compactedFiles = sfm.getCompactedfiles();
    if (currentFiles == null) currentFiles = Collections.emptySet();
    if (newFiles == null) newFiles = Collections.emptySet();
    if (compactedFiles == null) compactedFiles = Collections.emptySet();

    HashMap<StoreFileInfo, HStoreFile> currentFilesSet = new HashMap<>(currentFiles.size());
    for (HStoreFile sf : currentFiles) {
      currentFilesSet.put(sf.getFileInfo(), sf);
    }
    HashMap<StoreFileInfo, HStoreFile> compactedFilesSet = new HashMap<>(compactedFiles.size());
    for (HStoreFile sf : compactedFiles) {
      compactedFilesSet.put(sf.getFileInfo(), sf);
    }

    Set<StoreFileInfo> newFilesSet = new HashSet<StoreFileInfo>(newFiles);
    // Exclude the files that have already been compacted
    newFilesSet = Sets.difference(newFilesSet, compactedFilesSet.keySet());
    Set<StoreFileInfo> toBeAddedFiles = Sets.difference(newFilesSet, currentFilesSet.keySet());
    Set<StoreFileInfo> toBeRemovedFiles = Sets.difference(currentFilesSet.keySet(), newFilesSet);

    if (toBeAddedFiles.isEmpty() && toBeRemovedFiles.isEmpty()) {
      return;
    }

    LOG.info("Refreshing store files for region " + this.getRegionInfo().getRegionNameAsString()
      + " files to add: " + toBeAddedFiles + " files to remove: " + toBeRemovedFiles);

    Set<HStoreFile> toBeRemovedStoreFiles = new HashSet<>(toBeRemovedFiles.size());
    for (StoreFileInfo sfi : toBeRemovedFiles) {
      toBeRemovedStoreFiles.add(currentFilesSet.get(sfi));
    }

    // try to open the files
    List<HStoreFile> openedFiles = openStoreFiles(toBeAddedFiles);

    // propogate the file changes to the underlying store file manager
    replaceStoreFiles(toBeRemovedStoreFiles, openedFiles); //won't throw an exception

    // Advance the memstore read point to be at least the new store files seqIds so that
    // readers might pick it up. This assumes that the store is not getting any writes (otherwise
    // in-flight transactions might be made visible)
    if (!toBeAddedFiles.isEmpty()) {
      // we must have the max sequence id here as we do have several store files
      region.getMVCC().advanceTo(this.getMaxSequenceId().getAsLong());
    }

    completeCompaction(toBeRemovedStoreFiles);
  }

  @VisibleForTesting
  protected HStoreFile createStoreFileAndReader(final Path p) throws IOException {
    StoreFileInfo info = new StoreFileInfo(conf, this.getFileSystem(), p);
    return createStoreFileAndReader(info);
  }

  private HStoreFile createStoreFileAndReader(StoreFileInfo info) throws IOException {
    info.setRegionCoprocessorHost(this.region.getCoprocessorHost());
    HStoreFile storeFile = new HStoreFile(this.getFileSystem(), info, this.conf, this.cacheConf,
        this.family.getBloomFilterType(), isPrimaryReplicaStore());
    storeFile.initReader();
    return storeFile;
  }

  /**
   * This message intends to inform the MemStore that next coming updates
   * are going to be part of the replaying edits from WAL
   */
  public void startReplayingFromWAL(){
    this.memstore.startReplayingFromWAL();
  }

  /**
   * This message intends to inform the MemStore that the replaying edits from WAL
   * are done
   */
  public void stopReplayingFromWAL(){
    this.memstore.stopReplayingFromWAL();
  }

  /**
   * Adds a value to the memstore
   */
  public void add(final Cell cell, MemStoreSizing memstoreSizing) {
    lock.readLock().lock();
    try {
       this.memstore.add(cell, memstoreSizing);
    } finally {
      lock.readLock().unlock();
    }
  }

  /**
   * Adds the specified value to the memstore
   */
  public void add(final Iterable<Cell> cells, MemStoreSizing memstoreSizing) {
    lock.readLock().lock();
    try {
      memstore.add(cells, memstoreSizing);
    } finally {
      lock.readLock().unlock();
    }
  }

  @Override
  public long timeOfOldestEdit() {
    return memstore.timeOfOldestEdit();
  }

  /**
   * @return All store files.
   */
  @Override
  public Collection<HStoreFile> getStorefiles() {
    return this.storeEngine.getStoreFileManager().getStorefiles();
  }

  @Override
  public Collection<HStoreFile> getCompactedFiles() {
    return this.storeEngine.getStoreFileManager().getCompactedfiles();
  }

  /**
   * This throws a WrongRegionException if the HFile does not fit in this region, or an
   * InvalidHFileException if the HFile is not valid.
   */
  public void assertBulkLoadHFileOk(Path srcPath) throws IOException {
    HFile.Reader reader  = null;
    try {
      LOG.info("Validating hfile at " + srcPath + " for inclusion in "
          + "store " + this + " region " + this.getRegionInfo().getRegionNameAsString());
      reader = HFile.createReader(srcPath.getFileSystem(conf), srcPath, cacheConf,
        isPrimaryReplicaStore(), conf);
      reader.loadFileInfo();

      Optional<byte[]> firstKey = reader.getFirstRowKey();
      Preconditions.checkState(firstKey.isPresent(), "First key can not be null");
      Optional<Cell> lk = reader.getLastKey();
      Preconditions.checkState(lk.isPresent(), "Last key can not be null");
      byte[] lastKey =  CellUtil.cloneRow(lk.get());

      if (LOG.isDebugEnabled()) {
        LOG.debug("HFile bounds: first=" + Bytes.toStringBinary(firstKey.get()) +
            " last=" + Bytes.toStringBinary(lastKey));
        LOG.debug("Region bounds: first=" +
            Bytes.toStringBinary(getRegionInfo().getStartKey()) +
            " last=" + Bytes.toStringBinary(getRegionInfo().getEndKey()));
      }

      if (!this.getRegionInfo().containsRange(firstKey.get(), lastKey)) {
        throw new WrongRegionException(
            "Bulk load file " + srcPath.toString() + " does not fit inside region "
            + this.getRegionInfo().getRegionNameAsString());
      }

      if(reader.length() > conf.getLong(HConstants.HREGION_MAX_FILESIZE,
          HConstants.DEFAULT_MAX_FILE_SIZE)) {
        LOG.warn("Trying to bulk load hfile " + srcPath + " with size: " +
            reader.length() + " bytes can be problematic as it may lead to oversplitting.");
      }

      if (verifyBulkLoads) {
        long verificationStartTime = EnvironmentEdgeManager.currentTime();
        LOG.info("Full verification started for bulk load hfile: {}", srcPath);
        Cell prevCell = null;
        HFileScanner scanner = reader.getScanner(false, false, false);
        scanner.seekTo();
        do {
          Cell cell = scanner.getCell();
          if (prevCell != null) {
            if (comparator.compareRows(prevCell, cell) > 0) {
              throw new InvalidHFileException("Previous row is greater than"
                  + " current row: path=" + srcPath + " previous="
                  + CellUtil.getCellKeyAsString(prevCell) + " current="
                  + CellUtil.getCellKeyAsString(cell));
            }
            if (CellComparator.getInstance().compareFamilies(prevCell, cell) != 0) {
              throw new InvalidHFileException("Previous key had different"
                  + " family compared to current key: path=" + srcPath
                  + " previous="
                  + Bytes.toStringBinary(prevCell.getFamilyArray(), prevCell.getFamilyOffset(),
                      prevCell.getFamilyLength())
                  + " current="
                  + Bytes.toStringBinary(cell.getFamilyArray(), cell.getFamilyOffset(),
                      cell.getFamilyLength()));
            }
          }
          prevCell = cell;
        } while (scanner.next());
      LOG.info("Full verification complete for bulk load hfile: " + srcPath.toString()
         + " took " + (EnvironmentEdgeManager.currentTime() - verificationStartTime)
         + " ms");
      }
    } finally {
      if (reader != null) reader.close();
    }
  }

  /**
   * This method should only be called from Region. It is assumed that the ranges of values in the
   * HFile fit within the stores assigned region. (assertBulkLoadHFileOk checks this)
   *
   * @param srcPathStr
   * @param seqNum sequence Id associated with the HFile
   */
  public Pair<Path, Path> preBulkLoadHFile(String srcPathStr, long seqNum) throws IOException {
    Path srcPath = new Path(srcPathStr);
    return fs.bulkLoadStoreFile(getColumnFamilyName(), srcPath, seqNum);
  }

  public Path bulkLoadHFile(byte[] family, String srcPathStr, Path dstPath) throws IOException {
    Path srcPath = new Path(srcPathStr);
    try {
      fs.commitStoreFile(srcPath, dstPath);
    } finally {
      if (this.getCoprocessorHost() != null) {
        this.getCoprocessorHost().postCommitStoreFile(family, srcPath, dstPath);
      }
    }

    LOG.info("Loaded HFile " + srcPath + " into store '" + getColumnFamilyName() + "' as "
        + dstPath + " - updating store file list.");

    HStoreFile sf = createStoreFileAndReader(dstPath);
    bulkLoadHFile(sf);

    LOG.info("Successfully loaded store file {} into store {} (new location: {})",
        srcPath, this, dstPath);

    return dstPath;
  }

  public void bulkLoadHFile(StoreFileInfo fileInfo) throws IOException {
    HStoreFile sf = createStoreFileAndReader(fileInfo);
    bulkLoadHFile(sf);
  }

  private void bulkLoadHFile(HStoreFile sf) throws IOException {
    StoreFileReader r = sf.getReader();
    this.storeSize.addAndGet(r.length());
    this.totalUncompressedBytes.addAndGet(r.getTotalUncompressedBytes());

    // Append the new storefile into the list
    this.lock.writeLock().lock();
    try {
      this.storeEngine.getStoreFileManager().insertNewFiles(Lists.newArrayList(sf));
    } finally {
      // We need the lock, as long as we are updating the storeFiles
      // or changing the memstore. Let us release it before calling
      // notifyChangeReadersObservers. See HBASE-4485 for a possible
      // deadlock scenario that could have happened if continue to hold
      // the lock.
      this.lock.writeLock().unlock();
    }
    LOG.info("Loaded HFile " + sf.getFileInfo() + " into store '" + getColumnFamilyName());
    if (LOG.isTraceEnabled()) {
      String traceMessage = "BULK LOAD time,size,store size,store files ["
          + EnvironmentEdgeManager.currentTime() + "," + r.length() + "," + storeSize
          + "," + storeEngine.getStoreFileManager().getStorefileCount() + "]";
      LOG.trace(traceMessage);
    }
  }

  /**
   * Close all the readers We don't need to worry about subsequent requests because the Region holds
   * a write lock that will prevent any more reads or writes.
   * @return the {@link StoreFile StoreFiles} that were previously being used.
   * @throws IOException on failure
   */
  public ImmutableCollection<HStoreFile> close() throws IOException {
    this.archiveLock.lock();
    this.lock.writeLock().lock();
    try {
      // Clear so metrics doesn't find them.
      ImmutableCollection<HStoreFile> result = storeEngine.getStoreFileManager().clearFiles();
      Collection<HStoreFile> compactedfiles =
          storeEngine.getStoreFileManager().clearCompactedFiles();
      // clear the compacted files
      if (CollectionUtils.isNotEmpty(compactedfiles)) {
        removeCompactedfiles(compactedfiles);
      }
      if (!result.isEmpty()) {
        // initialize the thread pool for closing store files in parallel.
        ThreadPoolExecutor storeFileCloserThreadPool = this.region
            .getStoreFileOpenAndCloseThreadPool("StoreFileCloserThread-"
                + this.getColumnFamilyName());

        // close each store file in parallel
        CompletionService<Void> completionService =
          new ExecutorCompletionService<>(storeFileCloserThreadPool);
        for (HStoreFile f : result) {
          completionService.submit(new Callable<Void>() {
            @Override
            public Void call() throws IOException {
              boolean evictOnClose =
                  cacheConf != null? cacheConf.shouldEvictOnClose(): true;
              f.closeStoreFile(evictOnClose);
              return null;
            }
          });
        }

        IOException ioe = null;
        try {
          for (int i = 0; i < result.size(); i++) {
            try {
              Future<Void> future = completionService.take();
              future.get();
            } catch (InterruptedException e) {
              if (ioe == null) {
                ioe = new InterruptedIOException();
                ioe.initCause(e);
              }
            } catch (ExecutionException e) {
              if (ioe == null) ioe = new IOException(e.getCause());
            }
          }
        } finally {
          storeFileCloserThreadPool.shutdownNow();
        }
        if (ioe != null) throw ioe;
      }
      LOG.trace("Closed {}", this);
      return result;
    } finally {
      this.lock.writeLock().unlock();
      this.archiveLock.unlock();
    }
  }

  /**
   * Snapshot this stores memstore. Call before running
   * {@link #flushCache(long, MemStoreSnapshot, MonitoredTask, ThroughputController,
   * FlushLifeCycleTracker)}
   *  so it has some work to do.
   */
  void snapshot() {
    this.lock.writeLock().lock();
    try {
      this.memstore.snapshot();
    } finally {
      this.lock.writeLock().unlock();
    }
  }

  /**
   * Write out current snapshot. Presumes {@link #snapshot()} has been called previously.
   * @param logCacheFlushId flush sequence number
   * @param snapshot
   * @param status
   * @param throughputController
   * @return The path name of the tmp file to which the store was flushed
   * @throws IOException if exception occurs during process
   */
  protected List<Path> flushCache(final long logCacheFlushId, MemStoreSnapshot snapshot,
      MonitoredTask status, ThroughputController throughputController,
      FlushLifeCycleTracker tracker) throws IOException {
    // If an exception happens flushing, we let it out without clearing
    // the memstore snapshot.  The old snapshot will be returned when we say
    // 'snapshot', the next time flush comes around.
    // Retry after catching exception when flushing, otherwise server will abort
    // itself
    StoreFlusher flusher = storeEngine.getStoreFlusher();
    IOException lastException = null;
    for (int i = 0; i < flushRetriesNumber; i++) {
      try {
        List<Path> pathNames =
            flusher.flushSnapshot(snapshot, logCacheFlushId, status, throughputController, tracker);
        Path lastPathName = null;
        try {
          for (Path pathName : pathNames) {
            lastPathName = pathName;
            validateStoreFile(pathName);
          }
          return pathNames;
        } catch (Exception e) {
          LOG.warn("Failed validating store file {}, retrying num={}", lastPathName, i, e);
          if (e instanceof IOException) {
            lastException = (IOException) e;
          } else {
            lastException = new IOException(e);
          }
        }
      } catch (IOException e) {
        LOG.warn("Failed flushing store file, retrying num={}", i, e);
        lastException = e;
      }
      if (lastException != null && i < (flushRetriesNumber - 1)) {
        try {
          Thread.sleep(pauseTime);
        } catch (InterruptedException e) {
          IOException iie = new InterruptedIOException();
          iie.initCause(e);
          throw iie;
        }
      }
    }
    throw lastException;
  }

  /**
   * @param path The pathname of the tmp file into which the store was flushed
   * @param logCacheFlushId
   * @param status
   * @return store file created.
   * @throws IOException
   */
  private HStoreFile commitFile(Path path, long logCacheFlushId, MonitoredTask status)
      throws IOException {
    // Write-out finished successfully, move into the right spot
    Path dstPath = fs.commitStoreFile(getColumnFamilyName(), path);

    status.setStatus("Flushing " + this + ": reopening flushed file");
    HStoreFile sf = createStoreFileAndReader(dstPath);

    StoreFileReader r = sf.getReader();
    this.storeSize.addAndGet(r.length());
    this.totalUncompressedBytes.addAndGet(r.getTotalUncompressedBytes());

    if (LOG.isInfoEnabled()) {
      LOG.info("Added " + sf + ", entries=" + r.getEntries() +
        ", sequenceid=" + logCacheFlushId +
        ", filesize=" + TraditionalBinaryPrefix.long2String(r.length(), "", 1));
    }
    return sf;
  }

  /**
   * @param maxKeyCount
   * @param compression Compression algorithm to use
   * @param isCompaction whether we are creating a new file in a compaction
   * @param includeMVCCReadpoint - whether to include MVCC or not
   * @param includesTag - includesTag or not
   * @return Writer for a new StoreFile in the tmp dir.
   */
  // TODO : allow the Writer factory to create Writers of ShipperListener type only in case of
  // compaction
  public StoreFileWriter createWriterInTmp(long maxKeyCount, Compression.Algorithm compression,
      boolean isCompaction, boolean includeMVCCReadpoint, boolean includesTag,
      boolean shouldDropBehind) throws IOException {
    final CacheConfig writerCacheConf;
    if (isCompaction) {
      // Don't cache data on write on compactions.
      writerCacheConf = new CacheConfig(cacheConf);
      writerCacheConf.setCacheDataOnWrite(false);
    } else {
      writerCacheConf = cacheConf;
    }
    InetSocketAddress[] favoredNodes = null;
    if (region.getRegionServerServices() != null) {
      favoredNodes = region.getRegionServerServices().getFavoredNodesForRegion(
          region.getRegionInfo().getEncodedName());
    }
    HFileContext hFileContext = createFileContext(compression, includeMVCCReadpoint, includesTag,
      cryptoContext);
    Path familyTempDir = new Path(fs.getTempDir(), family.getNameAsString());
    StoreFileWriter.Builder builder = new StoreFileWriter.Builder(conf, writerCacheConf,
        this.getFileSystem())
            .withOutputDir(familyTempDir)
            .withComparator(comparator)
            .withBloomType(family.getBloomFilterType())
            .withMaxKeyCount(maxKeyCount)
            .withFavoredNodes(favoredNodes)
            .withFileContext(hFileContext)
            .withShouldDropCacheBehind(shouldDropBehind);
    return builder.build();
  }

  private HFileContext createFileContext(Compression.Algorithm compression,
      boolean includeMVCCReadpoint, boolean includesTag, Encryption.Context cryptoContext) {
    if (compression == null) {
      compression = HFile.DEFAULT_COMPRESSION_ALGORITHM;
    }
    HFileContext hFileContext = new HFileContextBuilder()
                                .withIncludesMvcc(includeMVCCReadpoint)
                                .withIncludesTags(includesTag)
                                .withCompression(compression)
                                .withCompressTags(family.isCompressTags())
                                .withChecksumType(checksumType)
                                .withBytesPerCheckSum(bytesPerChecksum)
                                .withBlockSize(blocksize)
                                .withHBaseCheckSum(true)
                                .withDataBlockEncoding(family.getDataBlockEncoding())
                                .withEncryptionContext(cryptoContext)
                                .withCreateTime(EnvironmentEdgeManager.currentTime())
                                .build();
    return hFileContext;
  }


  private long getTotalSize(Collection<HStoreFile> sfs) {
    return sfs.stream().mapToLong(sf -> sf.getReader().length()).sum();
  }

  /**
   * Change storeFiles adding into place the Reader produced by this new flush.
   * @param sfs Store files
   * @param snapshotId
   * @throws IOException
   * @return Whether compaction is required.
   */
  private boolean updateStorefiles(List<HStoreFile> sfs, long snapshotId) throws IOException {
    this.lock.writeLock().lock();
    try {
      this.storeEngine.getStoreFileManager().insertNewFiles(sfs);
      if (snapshotId > 0) {
        this.memstore.clearSnapshot(snapshotId);
      }
    } finally {
      // We need the lock, as long as we are updating the storeFiles
      // or changing the memstore. Let us release it before calling
      // notifyChangeReadersObservers. See HBASE-4485 for a possible
      // deadlock scenario that could have happened if continue to hold
      // the lock.
      this.lock.writeLock().unlock();
    }
    // notify to be called here - only in case of flushes
    notifyChangedReadersObservers(sfs);
    if (LOG.isTraceEnabled()) {
      long totalSize = getTotalSize(sfs);
      String traceMessage = "FLUSH time,count,size,store size,store files ["
          + EnvironmentEdgeManager.currentTime() + "," + sfs.size() + "," + totalSize
          + "," + storeSize + "," + storeEngine.getStoreFileManager().getStorefileCount() + "]";
      LOG.trace(traceMessage);
    }
    return needsCompaction();
  }

  /**
   * Notify all observers that set of Readers has changed.
   * @throws IOException
   */
  private void notifyChangedReadersObservers(List<HStoreFile> sfs) throws IOException {
    for (ChangedReadersObserver o : this.changedReaderObservers) {
      List<KeyValueScanner> memStoreScanners;
      this.lock.readLock().lock();
      try {
        memStoreScanners = this.memstore.getScanners(o.getReadPoint());
      } finally {
        this.lock.readLock().unlock();
      }
      o.updateReaders(sfs, memStoreScanners);
    }
  }

  /**
   * Get all scanners with no filtering based on TTL (that happens further down the line).
   * @param cacheBlocks cache the blocks or not
   * @param usePread true to use pread, false if not
   * @param isCompaction true if the scanner is created for compaction
   * @param matcher the scan query matcher
   * @param startRow the start row
   * @param stopRow the stop row
   * @param readPt the read point of the current scan
   * @return all scanners for this store
   */
  public List<KeyValueScanner> getScanners(boolean cacheBlocks, boolean isGet, boolean usePread,
      boolean isCompaction, ScanQueryMatcher matcher, byte[] startRow, byte[] stopRow, long readPt)
      throws IOException {
    return getScanners(cacheBlocks, usePread, isCompaction, matcher, startRow, true, stopRow, false,
      readPt);
  }

  /**
   * Get all scanners with no filtering based on TTL (that happens further down the line).
   * @param cacheBlocks cache the blocks or not
   * @param usePread true to use pread, false if not
   * @param isCompaction true if the scanner is created for compaction
   * @param matcher the scan query matcher
   * @param startRow the start row
   * @param includeStartRow true to include start row, false if not
   * @param stopRow the stop row
   * @param includeStopRow true to include stop row, false if not
   * @param readPt the read point of the current scan
   * @return all scanners for this store
   */
  public List<KeyValueScanner> getScanners(boolean cacheBlocks, boolean usePread,
      boolean isCompaction, ScanQueryMatcher matcher, byte[] startRow, boolean includeStartRow,
      byte[] stopRow, boolean includeStopRow, long readPt) throws IOException {
    Collection<HStoreFile> storeFilesToScan;
    List<KeyValueScanner> memStoreScanners;
    this.lock.readLock().lock();
    try {
      storeFilesToScan = this.storeEngine.getStoreFileManager().getFilesForScan(startRow,
        includeStartRow, stopRow, includeStopRow);
      memStoreScanners = this.memstore.getScanners(readPt);
    } finally {
      this.lock.readLock().unlock();
    }

    // First the store file scanners

    // TODO this used to get the store files in descending order,
    // but now we get them in ascending order, which I think is
    // actually more correct, since memstore get put at the end.
    List<StoreFileScanner> sfScanners = StoreFileScanner.getScannersForStoreFiles(storeFilesToScan,
      cacheBlocks, usePread, isCompaction, false, matcher, readPt);
    List<KeyValueScanner> scanners = new ArrayList<>(sfScanners.size() + 1);
    scanners.addAll(sfScanners);
    // Then the memstore scanners
    scanners.addAll(memStoreScanners);
    return scanners;
  }

  /**
   * Create scanners on the given files and if needed on the memstore with no filtering based on TTL
   * (that happens further down the line).
   * @param files the list of files on which the scanners has to be created
   * @param cacheBlocks cache the blocks or not
   * @param usePread true to use pread, false if not
   * @param isCompaction true if the scanner is created for compaction
   * @param matcher the scan query matcher
   * @param startRow the start row
   * @param stopRow the stop row
   * @param readPt the read point of the current scan
   * @param includeMemstoreScanner true if memstore has to be included
   * @return scanners on the given files and on the memstore if specified
   */
  public List<KeyValueScanner> getScanners(List<HStoreFile> files, boolean cacheBlocks,
      boolean isGet, boolean usePread, boolean isCompaction, ScanQueryMatcher matcher,
      byte[] startRow, byte[] stopRow, long readPt, boolean includeMemstoreScanner)
      throws IOException {
    return getScanners(files, cacheBlocks, usePread, isCompaction, matcher, startRow, true, stopRow,
      false, readPt, includeMemstoreScanner);
  }

  /**
   * Create scanners on the given files and if needed on the memstore with no filtering based on TTL
   * (that happens further down the line).
   * @param files the list of files on which the scanners has to be created
   * @param cacheBlocks ache the blocks or not
   * @param usePread true to use pread, false if not
   * @param isCompaction true if the scanner is created for compaction
   * @param matcher the scan query matcher
   * @param startRow the start row
   * @param includeStartRow true to include start row, false if not
   * @param stopRow the stop row
   * @param includeStopRow true to include stop row, false if not
   * @param readPt the read point of the current scan
   * @param includeMemstoreScanner true if memstore has to be included
   * @return scanners on the given files and on the memstore if specified
   */
  public List<KeyValueScanner> getScanners(List<HStoreFile> files, boolean cacheBlocks,
      boolean usePread, boolean isCompaction, ScanQueryMatcher matcher, byte[] startRow,
      boolean includeStartRow, byte[] stopRow, boolean includeStopRow, long readPt,
      boolean includeMemstoreScanner) throws IOException {
    List<KeyValueScanner> memStoreScanners = null;
    if (includeMemstoreScanner) {
      this.lock.readLock().lock();
      try {
        memStoreScanners = this.memstore.getScanners(readPt);
      } finally {
        this.lock.readLock().unlock();
      }
    }
    List<StoreFileScanner> sfScanners = StoreFileScanner.getScannersForStoreFiles(files,
      cacheBlocks, usePread, isCompaction, false, matcher, readPt);
    List<KeyValueScanner> scanners = new ArrayList<>(sfScanners.size() + 1);
    scanners.addAll(sfScanners);
    // Then the memstore scanners
    if (memStoreScanners != null) {
      scanners.addAll(memStoreScanners);
    }
    return scanners;
  }

  /**
   * @param o Observer who wants to know about changes in set of Readers
   */
  public void addChangedReaderObserver(ChangedReadersObserver o) {
    this.changedReaderObservers.add(o);
  }

  /**
   * @param o Observer no longer interested in changes in set of Readers.
   */
  public void deleteChangedReaderObserver(ChangedReadersObserver o) {
    // We don't check if observer present; it may not be (legitimately)
    this.changedReaderObservers.remove(o);
  }

  //////////////////////////////////////////////////////////////////////////////
  // Compaction
  //////////////////////////////////////////////////////////////////////////////

  /**
   * Compact the StoreFiles.  This method may take some time, so the calling
   * thread must be able to block for long periods.
   *
   * <p>During this time, the Store can work as usual, getting values from
   * StoreFiles and writing new StoreFiles from the memstore.
   *
   * Existing StoreFiles are not destroyed until the new compacted StoreFile is
   * completely written-out to disk.
   *
   * <p>The compactLock prevents multiple simultaneous compactions.
   * The structureLock prevents us from interfering with other write operations.
   *
   * <p>We don't want to hold the structureLock for the whole time, as a compact()
   * can be lengthy and we want to allow cache-flushes during this period.
   *
   * <p> Compaction event should be idempotent, since there is no IO Fencing for
   * the region directory in hdfs. A region server might still try to complete the
   * compaction after it lost the region. That is why the following events are carefully
   * ordered for a compaction:
   *  1. Compaction writes new files under region/.tmp directory (compaction output)
   *  2. Compaction atomically moves the temporary file under region directory
   *  3. Compaction appends a WAL edit containing the compaction input and output files.
   *  Forces sync on WAL.
   *  4. Compaction deletes the input files from the region directory.
   *
   * Failure conditions are handled like this:
   *  - If RS fails before 2, compaction wont complete. Even if RS lives on and finishes
   *  the compaction later, it will only write the new data file to the region directory.
   *  Since we already have this data, this will be idempotent but we will have a redundant
   *  copy of the data.
   *  - If RS fails between 2 and 3, the region will have a redundant copy of the data. The
   *  RS that failed won't be able to finish snyc() for WAL because of lease recovery in WAL.
   *  - If RS fails after 3, the region region server who opens the region will pick up the
   *  the compaction marker from the WAL and replay it by removing the compaction input files.
   *  Failed RS can also attempt to delete those files, but the operation will be idempotent
   *
   * See HBASE-2231 for details.
   *
   * @param compaction compaction details obtained from requestCompaction()
   * @throws IOException
   * @return Storefile we compacted into or null if we failed or opted out early.
   */
  public List<HStoreFile> compact(CompactionContext compaction,
    ThroughputController throughputController, User user) throws IOException {
    assert compaction != null;
    List<HStoreFile> sfs = null;
    CompactionRequestImpl cr = compaction.getRequest();
    try {
      // Do all sanity checking in here if we have a valid CompactionRequestImpl
      // because we need to clean up after it on the way out in a finally
      // block below
      long compactionStartTime = EnvironmentEdgeManager.currentTime();
      assert compaction.hasSelection();
      Collection<HStoreFile> filesToCompact = cr.getFiles();
      assert !filesToCompact.isEmpty();
      synchronized (filesCompacting) {
        // sanity check: we're compacting files that this store knows about
        // TODO: change this to LOG.error() after more debugging
        Preconditions.checkArgument(filesCompacting.containsAll(filesToCompact));
      }

      // Ready to go. Have list of files to compact.
      LOG.info("Starting compaction of " + filesToCompact +
        " into tmpdir=" + fs.getTempDir() + ", totalSize=" +
          TraditionalBinaryPrefix.long2String(cr.getSize(), "", 1));

      return doCompaction(cr, filesToCompact, user, compactionStartTime,
          compaction.compact(throughputController, user));
    } finally {
      finishCompactionRequest(cr);
    }
  }

  @VisibleForTesting
  protected List<HStoreFile> doCompaction(CompactionRequestImpl cr,
      Collection<HStoreFile> filesToCompact, User user, long compactionStartTime,
      List<Path> newFiles) throws IOException {
    // Do the steps necessary to complete the compaction.
    List<HStoreFile> sfs = moveCompactedFilesIntoPlace(cr, newFiles, user);
    writeCompactionWalRecord(filesToCompact, sfs);
    replaceStoreFiles(filesToCompact, sfs);
    if (cr.isMajor()) {
      majorCompactedCellsCount.addAndGet(getCompactionProgress().getTotalCompactingKVs());
      majorCompactedCellsSize.addAndGet(getCompactionProgress().totalCompactedSize);
    } else {
      compactedCellsCount.addAndGet(getCompactionProgress().getTotalCompactingKVs());
      compactedCellsSize.addAndGet(getCompactionProgress().totalCompactedSize);
    }
    long outputBytes = getTotalSize(sfs);

    // At this point the store will use new files for all new scanners.
    completeCompaction(filesToCompact); // update store size.

    long now = EnvironmentEdgeManager.currentTime();
    if (region.getRegionServerServices() != null
        && region.getRegionServerServices().getMetrics() != null) {
      region.getRegionServerServices().getMetrics().updateCompaction(cr.isMajor(),
          now - compactionStartTime, cr.getFiles().size(), newFiles.size(), cr.getSize(),
          outputBytes);
    }

    logCompactionEndMessage(cr, sfs, now, compactionStartTime);
    return sfs;
  }

  private List<HStoreFile> moveCompactedFilesIntoPlace(CompactionRequestImpl cr, List<Path> newFiles,
      User user) throws IOException {
    List<HStoreFile> sfs = new ArrayList<>(newFiles.size());
    for (Path newFile : newFiles) {
      assert newFile != null;
      HStoreFile sf = moveFileIntoPlace(newFile);
      if (this.getCoprocessorHost() != null) {
        getCoprocessorHost().postCompact(this, sf, cr.getTracker(), cr, user);
      }
      assert sf != null;
      sfs.add(sf);
    }
    return sfs;
  }

  // Package-visible for tests
  HStoreFile moveFileIntoPlace(Path newFile) throws IOException {
    validateStoreFile(newFile);
    // Move the file into the right spot
    Path destPath = fs.commitStoreFile(getColumnFamilyName(), newFile);
    return createStoreFileAndReader(destPath);
  }

  /**
   * Writes the compaction WAL record.
   * @param filesCompacted Files compacted (input).
   * @param newFiles Files from compaction.
   */
  private void writeCompactionWalRecord(Collection<HStoreFile> filesCompacted,
      Collection<HStoreFile> newFiles) throws IOException {
    if (region.getWAL() == null) {
      return;
    }
    List<Path> inputPaths =
        filesCompacted.stream().map(HStoreFile::getPath).collect(Collectors.toList());
    List<Path> outputPaths =
        newFiles.stream().map(HStoreFile::getPath).collect(Collectors.toList());
    RegionInfo info = this.region.getRegionInfo();
    CompactionDescriptor compactionDescriptor = ProtobufUtil.toCompactionDescriptor(info,
        family.getName(), inputPaths, outputPaths, fs.getStoreDir(getColumnFamilyDescriptor().getNameAsString()));
    // Fix reaching into Region to get the maxWaitForSeqId.
    // Does this method belong in Region altogether given it is making so many references up there?
    // Could be Region#writeCompactionMarker(compactionDescriptor);
    WALUtil.writeCompactionMarker(this.region.getWAL(), this.region.getReplicationScope(),
        this.region.getRegionInfo(), compactionDescriptor, this.region.getMVCC());
  }

  @VisibleForTesting
  void replaceStoreFiles(Collection<HStoreFile> compactedFiles, Collection<HStoreFile> result)
      throws IOException {
    this.lock.writeLock().lock();
    try {
      this.storeEngine.getStoreFileManager().addCompactionResults(compactedFiles, result);
      synchronized (filesCompacting) {
        filesCompacting.removeAll(compactedFiles);
      }
    } finally {
      this.lock.writeLock().unlock();
    }
  }

  /**
   * Log a very elaborate compaction completion message.
   * @param cr Request.
   * @param sfs Resulting files.
   * @param compactionStartTime Start time.
   */
  private void logCompactionEndMessage(
      CompactionRequestImpl cr, List<HStoreFile> sfs, long now, long compactionStartTime) {
    StringBuilder message = new StringBuilder(
      "Completed" + (cr.isMajor() ? " major" : "") + " compaction of "
      + cr.getFiles().size() + (cr.isAllFiles() ? " (all)" : "") + " file(s) in "
      + this + " of " + this.getRegionInfo().getShortNameToLog() + " into ");
    if (sfs.isEmpty()) {
      message.append("none, ");
    } else {
      for (HStoreFile sf: sfs) {
        message.append(sf.getPath().getName());
        message.append("(size=");
        message.append(TraditionalBinaryPrefix.long2String(sf.getReader().length(), "", 1));
        message.append("), ");
      }
    }
    message.append("total size for store is ")
      .append(StringUtils.TraditionalBinaryPrefix.long2String(storeSize.get(), "", 1))
      .append(". This selection was in queue for ")
      .append(StringUtils.formatTimeDiff(compactionStartTime, cr.getSelectionTime()))
      .append(", and took ").append(StringUtils.formatTimeDiff(now, compactionStartTime))
      .append(" to execute.");
    LOG.info(message.toString());
    if (LOG.isTraceEnabled()) {
      int fileCount = storeEngine.getStoreFileManager().getStorefileCount();
      long resultSize = getTotalSize(sfs);
      String traceMessage = "COMPACTION start,end,size out,files in,files out,store size,"
        + "store files [" + compactionStartTime + "," + now + "," + resultSize + ","
          + cr.getFiles().size() + "," + sfs.size() + "," +  storeSize + "," + fileCount + "]";
      LOG.trace(traceMessage);
    }
  }

  /**
   * Call to complete a compaction. Its for the case where we find in the WAL a compaction
   * that was not finished.  We could find one recovering a WAL after a regionserver crash.
   * See HBASE-2231.
   * @param compaction
   */
  public void replayCompactionMarker(CompactionDescriptor compaction, boolean pickCompactionFiles,
      boolean removeFiles) throws IOException {
    LOG.debug("Completing compaction from the WAL marker");
    List<String> compactionInputs = compaction.getCompactionInputList();
    List<String> compactionOutputs = Lists.newArrayList(compaction.getCompactionOutputList());

    // The Compaction Marker is written after the compaction is completed,
    // and the files moved into the region/family folder.
    //
    // If we crash after the entry is written, we may not have removed the
    // input files, but the output file is present.
    // (The unremoved input files will be removed by this function)
    //
    // If we scan the directory and the file is not present, it can mean that:
    //   - The file was manually removed by the user
    //   - The file was removed as consequence of subsequent compaction
    // so, we can't do anything with the "compaction output list" because those
    // files have already been loaded when opening the region (by virtue of
    // being in the store's folder) or they may be missing due to a compaction.

    String familyName = this.getColumnFamilyName();
    Set<String> inputFiles = new HashSet<>();
    for (String compactionInput : compactionInputs) {
      Path inputPath = fs.getStoreFilePath(familyName, compactionInput);
      inputFiles.add(inputPath.getName());
    }

    //some of the input files might already be deleted
    List<HStoreFile> inputStoreFiles = new ArrayList<>(compactionInputs.size());
    for (HStoreFile sf : this.getStorefiles()) {
      if (inputFiles.contains(sf.getPath().getName())) {
        inputStoreFiles.add(sf);
      }
    }

    // check whether we need to pick up the new files
    List<HStoreFile> outputStoreFiles = new ArrayList<>(compactionOutputs.size());

    if (pickCompactionFiles) {
      for (HStoreFile sf : this.getStorefiles()) {
        compactionOutputs.remove(sf.getPath().getName());
      }
      for (String compactionOutput : compactionOutputs) {
        StoreFileInfo storeFileInfo = fs.getStoreFileInfo(getColumnFamilyName(), compactionOutput);
        HStoreFile storeFile = createStoreFileAndReader(storeFileInfo);
        outputStoreFiles.add(storeFile);
      }
    }

    if (!inputStoreFiles.isEmpty() || !outputStoreFiles.isEmpty()) {
      LOG.info("Replaying compaction marker, replacing input files: " +
          inputStoreFiles + " with output files : " + outputStoreFiles);
      this.replaceStoreFiles(inputStoreFiles, outputStoreFiles);
      this.completeCompaction(inputStoreFiles);
    }
  }

  /**
   * This method tries to compact N recent files for testing.
   * Note that because compacting "recent" files only makes sense for some policies,
   * e.g. the default one, it assumes default policy is used. It doesn't use policy,
   * but instead makes a compaction candidate list by itself.
   * @param N Number of files.
   */
  @VisibleForTesting
  public void compactRecentForTestingAssumingDefaultPolicy(int N) throws IOException {
    List<HStoreFile> filesToCompact;
    boolean isMajor;

    this.lock.readLock().lock();
    try {
      synchronized (filesCompacting) {
        filesToCompact = Lists.newArrayList(storeEngine.getStoreFileManager().getStorefiles());
        if (!filesCompacting.isEmpty()) {
          // exclude all files older than the newest file we're currently
          // compacting. this allows us to preserve contiguity (HBASE-2856)
          HStoreFile last = filesCompacting.get(filesCompacting.size() - 1);
          int idx = filesToCompact.indexOf(last);
          Preconditions.checkArgument(idx != -1);
          filesToCompact.subList(0, idx + 1).clear();
        }
        int count = filesToCompact.size();
        if (N > count) {
          throw new RuntimeException("Not enough files");
        }

        filesToCompact = filesToCompact.subList(count - N, count);
        isMajor = (filesToCompact.size() == storeEngine.getStoreFileManager().getStorefileCount());
        filesCompacting.addAll(filesToCompact);
        Collections.sort(filesCompacting, storeEngine.getStoreFileManager()
            .getStoreFileComparator());
      }
    } finally {
      this.lock.readLock().unlock();
    }

    try {
      // Ready to go. Have list of files to compact.
      List<Path> newFiles = ((DefaultCompactor)this.storeEngine.getCompactor())
          .compactForTesting(filesToCompact, isMajor);
      for (Path newFile: newFiles) {
        // Move the compaction into place.
        HStoreFile sf = moveFileIntoPlace(newFile);
        if (this.getCoprocessorHost() != null) {
          this.getCoprocessorHost().postCompact(this, sf, null, null, null);
        }
        replaceStoreFiles(filesToCompact, Collections.singletonList(sf));
        completeCompaction(filesToCompact);
      }
    } finally {
      synchronized (filesCompacting) {
        filesCompacting.removeAll(filesToCompact);
      }
    }
  }

  @Override
  public boolean hasReferences() {
    List<HStoreFile> reloadedStoreFiles = null;
    try {
      // Reloading the store files from file system due to HBASE-20940. As split can happen with an
      // region which has references
      reloadedStoreFiles = loadStoreFiles();
      return StoreUtils.hasReferences(reloadedStoreFiles);
    } catch (IOException ioe) {
      LOG.error("Error trying to determine if store has references, assuming references exists",
        ioe);
      return true;
    } finally {
      if (reloadedStoreFiles != null) {
        for (HStoreFile storeFile : reloadedStoreFiles) {
          try {
            storeFile.closeStoreFile(false);
          } catch (IOException ioe) {
            LOG.warn("Encountered exception closing " + storeFile + ": " + ioe.getMessage());
            // continue with closing the remaining store files
          }
        }
      }
    }
  }

  /**
   * getter for CompactionProgress object
   * @return CompactionProgress object; can be null
   */
  public CompactionProgress getCompactionProgress() {
    return this.storeEngine.getCompactor().getProgress();
  }

  @Override
  public boolean shouldPerformMajorCompaction() throws IOException {
    for (HStoreFile sf : this.storeEngine.getStoreFileManager().getStorefiles()) {
      // TODO: what are these reader checks all over the place?
      if (sf.getReader() == null) {
        LOG.debug("StoreFile {} has null Reader", sf);
        return false;
      }
    }
    return storeEngine.getCompactionPolicy().shouldPerformMajorCompaction(
        this.storeEngine.getStoreFileManager().getStorefiles());
  }

  public Optional<CompactionContext> requestCompaction() throws IOException {
    return requestCompaction(NO_PRIORITY, CompactionLifeCycleTracker.DUMMY, null);
  }

  public Optional<CompactionContext> requestCompaction(int priority,
      CompactionLifeCycleTracker tracker, User user) throws IOException {
    // don't even select for compaction if writes are disabled
    if (!this.areWritesEnabled()) {
      return Optional.empty();
    }
    // Before we do compaction, try to get rid of unneeded files to simplify things.
    removeUnneededFiles();

    final CompactionContext compaction = storeEngine.createCompaction();
    CompactionRequestImpl request = null;
    this.lock.readLock().lock();
    try {
      synchronized (filesCompacting) {
        // First, see if coprocessor would want to override selection.
        if (this.getCoprocessorHost() != null) {
          final List<HStoreFile> candidatesForCoproc = compaction.preSelect(this.filesCompacting);
          boolean override = getCoprocessorHost().preCompactSelection(this,
              candidatesForCoproc, tracker, user);
          if (override) {
            // Coprocessor is overriding normal file selection.
            compaction.forceSelect(new CompactionRequestImpl(candidatesForCoproc));
          }
        }

        // Normal case - coprocessor is not overriding file selection.
        if (!compaction.hasSelection()) {
          boolean isUserCompaction = priority == Store.PRIORITY_USER;
          boolean mayUseOffPeak = offPeakHours.isOffPeakHour() &&
              offPeakCompactionTracker.compareAndSet(false, true);
          try {
            compaction.select(this.filesCompacting, isUserCompaction,
              mayUseOffPeak, forceMajor && filesCompacting.isEmpty());
          } catch (IOException e) {
            if (mayUseOffPeak) {
              offPeakCompactionTracker.set(false);
            }
            throw e;
          }
          assert compaction.hasSelection();
          if (mayUseOffPeak && !compaction.getRequest().isOffPeak()) {
            // Compaction policy doesn't want to take advantage of off-peak.
            offPeakCompactionTracker.set(false);
          }
        }
        if (this.getCoprocessorHost() != null) {
          this.getCoprocessorHost().postCompactSelection(
              this, ImmutableList.copyOf(compaction.getRequest().getFiles()), tracker,
              compaction.getRequest(), user);
        }
        // Finally, we have the resulting files list. Check if we have any files at all.
        request = compaction.getRequest();
        Collection<HStoreFile> selectedFiles = request.getFiles();
        if (selectedFiles.isEmpty()) {
          return Optional.empty();
        }

        addToCompactingFiles(selectedFiles);

        // If we're enqueuing a major, clear the force flag.
        this.forceMajor = this.forceMajor && !request.isMajor();

        // Set common request properties.
        // Set priority, either override value supplied by caller or from store.
        request.setPriority((priority != Store.NO_PRIORITY) ? priority : getCompactPriority());
        request.setDescription(getRegionInfo().getRegionNameAsString(), getColumnFamilyName());
        request.setTracker(tracker);
      }
    } finally {
      this.lock.readLock().unlock();
    }

    if (LOG.isDebugEnabled()) {
      LOG.debug(getRegionInfo().getEncodedName() + " - " + getColumnFamilyName()
          + ": Initiating " + (request.isMajor() ? "major" : "minor") + " compaction"
          + (request.isAllFiles() ? " (all files)" : ""));
    }
    this.region.reportCompactionRequestStart(request.isMajor());
    return Optional.of(compaction);
  }

  /** Adds the files to compacting files. filesCompacting must be locked. */
  private void addToCompactingFiles(Collection<HStoreFile> filesToAdd) {
    if (CollectionUtils.isEmpty(filesToAdd)) {
      return;
    }
    // Check that we do not try to compact the same StoreFile twice.
    if (!Collections.disjoint(filesCompacting, filesToAdd)) {
      Preconditions.checkArgument(false, "%s overlaps with %s", filesToAdd, filesCompacting);
    }
    filesCompacting.addAll(filesToAdd);
    Collections.sort(filesCompacting, storeEngine.getStoreFileManager().getStoreFileComparator());
  }

  private void removeUnneededFiles() throws IOException {
    if (!conf.getBoolean("hbase.store.delete.expired.storefile", true)) return;
    if (getColumnFamilyDescriptor().getMinVersions() > 0) {
      LOG.debug("Skipping expired store file removal due to min version being {}",
          getColumnFamilyDescriptor().getMinVersions());
      return;
    }
    this.lock.readLock().lock();
    Collection<HStoreFile> delSfs = null;
    try {
      synchronized (filesCompacting) {
        long cfTtl = getStoreFileTtl();
        if (cfTtl != Long.MAX_VALUE) {
          delSfs = storeEngine.getStoreFileManager().getUnneededFiles(
              EnvironmentEdgeManager.currentTime() - cfTtl, filesCompacting);
          addToCompactingFiles(delSfs);
        }
      }
    } finally {
      this.lock.readLock().unlock();
    }

    if (CollectionUtils.isEmpty(delSfs)) {
      return;
    }

    Collection<HStoreFile> newFiles = Collections.emptyList(); // No new files.
    writeCompactionWalRecord(delSfs, newFiles);
    replaceStoreFiles(delSfs, newFiles);
    completeCompaction(delSfs);
    LOG.info("Completed removal of " + delSfs.size() + " unnecessary (expired) file(s) in "
        + this + " of " + this.getRegionInfo().getRegionNameAsString()
        + "; total size for store is "
        + TraditionalBinaryPrefix.long2String(storeSize.get(), "", 1));
  }

  public void cancelRequestedCompaction(CompactionContext compaction) {
    finishCompactionRequest(compaction.getRequest());
  }

  private void finishCompactionRequest(CompactionRequestImpl cr) {
    this.region.reportCompactionRequestEnd(cr.isMajor(), cr.getFiles().size(), cr.getSize());
    if (cr.isOffPeak()) {
      offPeakCompactionTracker.set(false);
      cr.setOffPeak(false);
    }
    synchronized (filesCompacting) {
      filesCompacting.removeAll(cr.getFiles());
    }
  }

  /**
   * Validates a store file by opening and closing it. In HFileV2 this should not be an expensive
   * operation.
   * @param path the path to the store file
   */
  private void validateStoreFile(Path path) throws IOException {
    HStoreFile storeFile = null;
    try {
      storeFile = createStoreFileAndReader(path);
    } catch (IOException e) {
      LOG.error("Failed to open store file : {}, keeping it in tmp location", path, e);
      throw e;
    } finally {
      if (storeFile != null) {
        storeFile.closeStoreFile(false);
      }
    }
  }

  /**
   * <p>It works by processing a compaction that's been written to disk.
   *
   * <p>It is usually invoked at the end of a compaction, but might also be
   * invoked at HStore startup, if the prior execution died midway through.
   *
   * <p>Moving the compacted TreeMap into place means:
   * <pre>
   * 1) Unload all replaced StoreFile, close and collect list to delete.
   * 2) Compute new store size
   * </pre>
   *
   * @param compactedFiles list of files that were compacted
   */
  @VisibleForTesting
  protected void completeCompaction(Collection<HStoreFile> compactedFiles)
    throws IOException {
    this.storeSize.set(0L);
    this.totalUncompressedBytes.set(0L);
    for (HStoreFile hsf : this.storeEngine.getStoreFileManager().getStorefiles()) {
      StoreFileReader r = hsf.getReader();
      if (r == null) {
        LOG.warn("StoreFile {} has a null Reader", hsf);
        continue;
      }
      this.storeSize.addAndGet(r.length());
      this.totalUncompressedBytes.addAndGet(r.getTotalUncompressedBytes());
    }
  }

  /*
   * @param wantedVersions How many versions were asked for.
   * @return wantedVersions or this families' {@link HConstants#VERSIONS}.
   */
  int versionsToReturn(final int wantedVersions) {
    if (wantedVersions <= 0) {
      throw new IllegalArgumentException("Number of versions must be > 0");
    }
    // Make sure we do not return more than maximum versions for this store.
    int maxVersions = this.family.getMaxVersions();
    return wantedVersions > maxVersions ? maxVersions: wantedVersions;
  }

  @Override
  public boolean canSplit() {
    this.lock.readLock().lock();
    try {
      // Not split-able if we find a reference store file present in the store.
      boolean result = !hasReferences();
      if (!result) {
        LOG.trace("Not splittable; has references: {}", this);
      }
      return result;
    } finally {
      this.lock.readLock().unlock();
    }
  }

  /**
   * Determines if Store should be split.
   */
  public Optional<byte[]> getSplitPoint() {
    this.lock.readLock().lock();
    try {
      // Should already be enforced by the split policy!
      assert !this.getRegionInfo().isMetaRegion();
      // Not split-able if we find a reference store file present in the store.
      if (hasReferences()) {
        LOG.trace("Not splittable; has references: {}", this);
        return Optional.empty();
      }
      return this.storeEngine.getStoreFileManager().getSplitPoint();
    } catch(IOException e) {
      LOG.warn("Failed getting store size for {}", this, e);
    } finally {
      this.lock.readLock().unlock();
    }
    return Optional.empty();
  }

  @Override
  public long getLastCompactSize() {
    return this.lastCompactSize;
  }

  @Override
  public long getSize() {
    return storeSize.get();
  }

  public void triggerMajorCompaction() {
    this.forceMajor = true;
  }

  //////////////////////////////////////////////////////////////////////////////
  // File administration
  //////////////////////////////////////////////////////////////////////////////

  /**
   * Return a scanner for both the memstore and the HStore files. Assumes we are not in a
   * compaction.
   * @param scan Scan to apply when scanning the stores
   * @param targetCols columns to scan
   * @return a scanner over the current key values
   * @throws IOException on failure
   */
  public KeyValueScanner getScanner(Scan scan, final NavigableSet<byte[]> targetCols, long readPt)
      throws IOException {
    lock.readLock().lock();
    try {
      ScanInfo scanInfo;
      if (this.getCoprocessorHost() != null) {
        scanInfo = this.getCoprocessorHost().preStoreScannerOpen(this);
      } else {
        scanInfo = getScanInfo();
      }
      return createScanner(scan, scanInfo, targetCols, readPt);
    } finally {
      lock.readLock().unlock();
    }
  }

  // HMobStore will override this method to return its own implementation.
  protected KeyValueScanner createScanner(Scan scan, ScanInfo scanInfo,
      NavigableSet<byte[]> targetCols, long readPt) throws IOException {
    return scan.isReversed() ? new ReversedStoreScanner(this, scanInfo, scan, targetCols, readPt)
        : new StoreScanner(this, scanInfo, scan, targetCols, readPt);
  }

  /**
   * Recreates the scanners on the current list of active store file scanners
   * @param currentFileScanners the current set of active store file scanners
   * @param cacheBlocks cache the blocks or not
   * @param usePread use pread or not
   * @param isCompaction is the scanner for compaction
   * @param matcher the scan query matcher
   * @param startRow the scan's start row
   * @param includeStartRow should the scan include the start row
   * @param stopRow the scan's stop row
   * @param includeStopRow should the scan include the stop row
   * @param readPt the read point of the current scane
   * @param includeMemstoreScanner whether the current scanner should include memstorescanner
   * @return list of scanners recreated on the current Scanners
   * @throws IOException
   */
  public List<KeyValueScanner> recreateScanners(List<KeyValueScanner> currentFileScanners,
      boolean cacheBlocks, boolean usePread, boolean isCompaction, ScanQueryMatcher matcher,
      byte[] startRow, boolean includeStartRow, byte[] stopRow, boolean includeStopRow, long readPt,
      boolean includeMemstoreScanner) throws IOException {
    this.lock.readLock().lock();
    try {
      Map<String, HStoreFile> name2File =
          new HashMap<>(getStorefilesCount() + getCompactedFilesCount());
      for (HStoreFile file : getStorefiles()) {
        name2File.put(file.getFileInfo().getActiveFileName(), file);
      }
      Collection<HStoreFile> compactedFiles = getCompactedFiles();
      for (HStoreFile file : IterableUtils.emptyIfNull(compactedFiles)) {
        name2File.put(file.getFileInfo().getActiveFileName(), file);
      }
      List<HStoreFile> filesToReopen = new ArrayList<>();
      for (KeyValueScanner kvs : currentFileScanners) {
        assert kvs.isFileScanner();
        if (kvs.peek() == null) {
          continue;
        }
        filesToReopen.add(name2File.get(kvs.getFilePath().getName()));
      }
      if (filesToReopen.isEmpty()) {
        return null;
      }
      return getScanners(filesToReopen, cacheBlocks, false, false, matcher, startRow,
        includeStartRow, stopRow, includeStopRow, readPt, false);
    } finally {
      this.lock.readLock().unlock();
    }
  }

  @Override
  public String toString() {
    return this.getColumnFamilyName();
  }

  @Override
  public int getStorefilesCount() {
    return this.storeEngine.getStoreFileManager().getStorefileCount();
  }

  @Override
  public int getCompactedFilesCount() {
    return this.storeEngine.getStoreFileManager().getCompactedFilesCount();
  }

  private LongStream getStoreFileAgeStream() {
    return this.storeEngine.getStoreFileManager().getStorefiles().stream().filter(sf -> {
      if (sf.getReader() == null) {
        LOG.warn("StoreFile {} has a null Reader", sf);
        return false;
      } else {
        return true;
      }
    }).filter(HStoreFile::isHFile).mapToLong(sf -> sf.getFileInfo().getCreatedTimestamp())
        .map(t -> EnvironmentEdgeManager.currentTime() - t);
  }

  @Override
  public OptionalLong getMaxStoreFileAge() {
    return getStoreFileAgeStream().max();
  }

  @Override
  public OptionalLong getMinStoreFileAge() {
    return getStoreFileAgeStream().min();
  }

  @Override
  public OptionalDouble getAvgStoreFileAge() {
    return getStoreFileAgeStream().average();
  }

  @Override
  public long getNumReferenceFiles() {
    return this.storeEngine.getStoreFileManager().getStorefiles().stream()
        .filter(HStoreFile::isReference).count();
  }

  @Override
  public long getNumHFiles() {
    return this.storeEngine.getStoreFileManager().getStorefiles().stream()
        .filter(HStoreFile::isHFile).count();
  }

  @Override
  public long getStoreSizeUncompressed() {
    return this.totalUncompressedBytes.get();
  }

  @Override
  public long getStorefilesSize() {
    // Include all StoreFiles
    return getStorefilesSize(storeFile -> true);
  }

  @Override
  public long getHFilesSize() {
    // Include only StoreFiles which are HFiles
    return getStorefilesSize(storeFile -> storeFile.isHFile());
  }

  private long getStorefilesSize(Predicate<HStoreFile> predicate) {
    return this.storeEngine.getStoreFileManager().getStorefiles().stream().filter(sf -> {
      if (sf.getReader() == null) {
        LOG.warn("StoreFile {} has a null Reader", sf);
        return false;
      } else {
        return true;
      }
    }).filter(predicate).mapToLong(sf -> sf.getReader().length()).sum();
  }

  private long getStoreFileFieldSize(ToLongFunction<StoreFileReader> f) {
    return this.storeEngine.getStoreFileManager().getStorefiles().stream().filter(sf -> {
      if (sf.getReader() == null) {
        LOG.warn("StoreFile {} has a null Reader", sf);
        return false;
      } else {
        return true;
      }
    }).map(HStoreFile::getReader).mapToLong(f).sum();
  }

  @Override
  public long getStorefilesRootLevelIndexSize() {
    return getStoreFileFieldSize(StoreFileReader::indexSize);
  }

  @Override
  public long getTotalStaticIndexSize() {
    return getStoreFileFieldSize(StoreFileReader::getUncompressedDataIndexSize);
  }

  @Override
  public long getTotalStaticBloomSize() {
    return getStoreFileFieldSize(StoreFileReader::getTotalBloomSize);
  }

  @Override
  public MemStoreSize getMemStoreSize() {
    return this.memstore.size();
  }

  @Override
  public int getCompactPriority() {
    int priority = this.storeEngine.getStoreFileManager().getStoreCompactionPriority();
    if (priority == PRIORITY_USER) {
      LOG.warn("Compaction priority is USER despite there being no user compaction");
    }
    return priority;
  }

  public boolean throttleCompaction(long compactionSize) {
    return storeEngine.getCompactionPolicy().throttleCompaction(compactionSize);
  }

  public HRegion getHRegion() {
    return this.region;
  }

  public RegionCoprocessorHost getCoprocessorHost() {
    return this.region.getCoprocessorHost();
  }

  @Override
  public RegionInfo getRegionInfo() {
    return this.fs.getRegionInfo();
  }

  @Override
  public boolean areWritesEnabled() {
    return this.region.areWritesEnabled();
  }

  @Override
  public long getSmallestReadPoint() {
    return this.region.getSmallestReadPoint();
  }

  /**
   * Adds or replaces the specified KeyValues.
   * <p>
   * For each KeyValue specified, if a cell with the same row, family, and qualifier exists in
   * MemStore, it will be replaced. Otherwise, it will just be inserted to MemStore.
   * <p>
   * This operation is atomic on each KeyValue (row/family/qualifier) but not necessarily atomic
   * across all of them.
   * @param readpoint readpoint below which we can safely remove duplicate KVs
   * @throws IOException
   */
  public void upsert(Iterable<Cell> cells, long readpoint, MemStoreSizing memstoreSizing)
      throws IOException {
    this.lock.readLock().lock();
    try {
      this.memstore.upsert(cells, readpoint, memstoreSizing);
    } finally {
      this.lock.readLock().unlock();
    }
  }

  public StoreFlushContext createFlushContext(long cacheFlushId, FlushLifeCycleTracker tracker) {
    return new StoreFlusherImpl(cacheFlushId, tracker);
  }

  private final class StoreFlusherImpl implements StoreFlushContext {

    private final FlushLifeCycleTracker tracker;
    private final long cacheFlushSeqNum;
    private MemStoreSnapshot snapshot;
    private List<Path> tempFiles;
    private List<Path> committedFiles;
    private long cacheFlushCount;
    private long cacheFlushSize;
    private long outputFileSize;

    private StoreFlusherImpl(long cacheFlushSeqNum, FlushLifeCycleTracker tracker) {
      this.cacheFlushSeqNum = cacheFlushSeqNum;
      this.tracker = tracker;
    }

    /**
     * This is not thread safe. The caller should have a lock on the region or the store.
     * If necessary, the lock can be added with the patch provided in HBASE-10087
     */
    @Override
    public MemStoreSize prepare() {
      // passing the current sequence number of the wal - to allow bookkeeping in the memstore
      this.snapshot = memstore.snapshot();
      this.cacheFlushCount = snapshot.getCellsCount();
      this.cacheFlushSize = snapshot.getDataSize();
      committedFiles = new ArrayList<>(1);
      return snapshot.getMemStoreSize();
    }

    @Override
    public void flushCache(MonitoredTask status) throws IOException {
      RegionServerServices rsService = region.getRegionServerServices();
      ThroughputController throughputController =
          rsService == null ? null : rsService.getFlushThroughputController();
      tempFiles =
          HStore.this.flushCache(cacheFlushSeqNum, snapshot, status, throughputController, tracker);
    }

    @Override
    public boolean commit(MonitoredTask status) throws IOException {
      if (CollectionUtils.isEmpty(this.tempFiles)) {
        return false;
      }
      List<HStoreFile> storeFiles = new ArrayList<>(this.tempFiles.size());
      for (Path storeFilePath : tempFiles) {
        try {
          HStoreFile sf = HStore.this.commitFile(storeFilePath, cacheFlushSeqNum, status);
          outputFileSize += sf.getReader().length();
          storeFiles.add(sf);
        } catch (IOException ex) {
          LOG.error("Failed to commit store file {}", storeFilePath, ex);
          // Try to delete the files we have committed before.
          for (HStoreFile sf : storeFiles) {
            Path pathToDelete = sf.getPath();
            try {
              sf.deleteStoreFile();
            } catch (IOException deleteEx) {
              LOG.error(HBaseMarkers.FATAL, "Failed to delete store file we committed, "
                  + "halting {}", pathToDelete, ex);
              Runtime.getRuntime().halt(1);
            }
          }
          throw new IOException("Failed to commit the flush", ex);
        }
      }

      for (HStoreFile sf : storeFiles) {
        if (HStore.this.getCoprocessorHost() != null) {
          HStore.this.getCoprocessorHost().postFlush(HStore.this, sf, tracker);
        }
        committedFiles.add(sf.getPath());
      }

      HStore.this.flushedCellsCount.addAndGet(cacheFlushCount);
      HStore.this.flushedCellsSize.addAndGet(cacheFlushSize);
      HStore.this.flushedOutputFileSize.addAndGet(outputFileSize);

      // Add new file to store files.  Clear snapshot too while we have the Store write lock.
      return HStore.this.updateStorefiles(storeFiles, snapshot.getId());
    }

    @Override
    public long getOutputFileSize() {
      return outputFileSize;
    }

    @Override
    public List<Path> getCommittedFiles() {
      return committedFiles;
    }

    /**
     * Similar to commit, but called in secondary region replicas for replaying the
     * flush cache from primary region. Adds the new files to the store, and drops the
     * snapshot depending on dropMemstoreSnapshot argument.
     * @param fileNames names of the flushed files
     * @param dropMemstoreSnapshot whether to drop the prepared memstore snapshot
     * @throws IOException
     */
    @Override
    public void replayFlush(List<String> fileNames, boolean dropMemstoreSnapshot)
        throws IOException {
      List<HStoreFile> storeFiles = new ArrayList<>(fileNames.size());
      for (String file : fileNames) {
        // open the file as a store file (hfile link, etc)
        StoreFileInfo storeFileInfo = fs.getStoreFileInfo(getColumnFamilyName(), file);
        HStoreFile storeFile = createStoreFileAndReader(storeFileInfo);
        storeFiles.add(storeFile);
        HStore.this.storeSize.addAndGet(storeFile.getReader().length());
        HStore.this.totalUncompressedBytes
            .addAndGet(storeFile.getReader().getTotalUncompressedBytes());
        if (LOG.isInfoEnabled()) {
          LOG.info("Region: " + HStore.this.getRegionInfo().getEncodedName() +
            " added " + storeFile + ", entries=" + storeFile.getReader().getEntries() +
              ", sequenceid=" + +storeFile.getReader().getSequenceID() + ", filesize="
              + TraditionalBinaryPrefix.long2String(storeFile.getReader().length(), "", 1));
        }
      }

      long snapshotId = -1; // -1 means do not drop
      if (dropMemstoreSnapshot && snapshot != null) {
        snapshotId = snapshot.getId();
        snapshot.close();
      }
      HStore.this.updateStorefiles(storeFiles, snapshotId);
    }

    /**
     * Abort the snapshot preparation. Drops the snapshot if any.
     * @throws IOException
     */
    @Override
    public void abort() throws IOException {
      if (snapshot != null) {
        //We need to close the snapshot when aborting, otherwise, the segment scanner
        //won't be closed. If we are using MSLAB, the chunk referenced by those scanners
        //can't be released, thus memory leak
        snapshot.close();
        HStore.this.updateStorefiles(Collections.emptyList(), snapshot.getId());
      }
    }
  }

  @Override
  public boolean needsCompaction() {
    List<HStoreFile> filesCompactingClone = null;
    synchronized (filesCompacting) {
      filesCompactingClone = Lists.newArrayList(filesCompacting);
    }
    return this.storeEngine.needsCompaction(filesCompactingClone);
  }

  /**
   * Used for tests.
   * @return cache configuration for this Store.
   */
  @VisibleForTesting
  public CacheConfig getCacheConfig() {
    return this.cacheConf;
  }

  public static final long FIXED_OVERHEAD =
      ClassSize.align(ClassSize.OBJECT + (26 * ClassSize.REFERENCE) + (2 * Bytes.SIZEOF_LONG)
              + (5 * Bytes.SIZEOF_INT) + (2 * Bytes.SIZEOF_BOOLEAN));

  public static final long DEEP_OVERHEAD = ClassSize.align(FIXED_OVERHEAD
      + ClassSize.OBJECT + ClassSize.REENTRANT_LOCK
      + ClassSize.CONCURRENT_SKIPLISTMAP
      + ClassSize.CONCURRENT_SKIPLISTMAP_ENTRY + ClassSize.OBJECT
      + ScanInfo.FIXED_OVERHEAD);

  @Override
  public long heapSize() {
    MemStoreSize memstoreSize = this.memstore.size();
    return DEEP_OVERHEAD + memstoreSize.getHeapSize();
  }

  @Override
  public CellComparator getComparator() {
    return comparator;
  }

  public ScanInfo getScanInfo() {
    return scanInfo;
  }

  /**
   * Set scan info, used by test
   * @param scanInfo new scan info to use for test
   */
  void setScanInfo(ScanInfo scanInfo) {
    this.scanInfo = scanInfo;
  }

  @Override
  public boolean hasTooManyStoreFiles() {
    return getStorefilesCount() > this.blockingFileCount;
  }

  @Override
  public long getFlushedCellsCount() {
    return flushedCellsCount.get();
  }

  @Override
  public long getFlushedCellsSize() {
    return flushedCellsSize.get();
  }

  @Override
  public long getFlushedOutputFileSize() {
    return flushedOutputFileSize.get();
  }

  @Override
  public long getCompactedCellsCount() {
    return compactedCellsCount.get();
  }

  @Override
  public long getCompactedCellsSize() {
    return compactedCellsSize.get();
  }

  @Override
  public long getMajorCompactedCellsCount() {
    return majorCompactedCellsCount.get();
  }

  @Override
  public long getMajorCompactedCellsSize() {
    return majorCompactedCellsSize.get();
  }

  /**
   * Returns the StoreEngine that is backing this concrete implementation of Store.
   * @return Returns the {@link StoreEngine} object used internally inside this HStore object.
   */
  @VisibleForTesting
  public StoreEngine<?, ?, ?, ?> getStoreEngine() {
    return this.storeEngine;
  }

  protected OffPeakHours getOffPeakHours() {
    return this.offPeakHours;
  }

  /**
   * {@inheritDoc}
   */
  @Override
  public void onConfigurationChange(Configuration conf) {
    this.conf = new CompoundConfiguration()
            .add(conf)
            .addBytesMap(family.getValues());
    this.storeEngine.compactionPolicy.setConf(conf);
    this.offPeakHours = OffPeakHours.getInstance(conf);
  }

  /**
   * {@inheritDoc}
   */
  @Override
  public void registerChildren(ConfigurationManager manager) {
    // No children to register
  }

  /**
   * {@inheritDoc}
   */
  @Override
  public void deregisterChildren(ConfigurationManager manager) {
    // No children to deregister
  }

  @Override
  public double getCompactionPressure() {
    return storeEngine.getStoreFileManager().getCompactionPressure();
  }

  @Override
  public boolean isPrimaryReplicaStore() {
    return getRegionInfo().getReplicaId() == RegionInfo.DEFAULT_REPLICA_ID;
  }

  /**
   * Sets the store up for a region level snapshot operation.
   * @see #postSnapshotOperation()
   */
  public void preSnapshotOperation() {
    archiveLock.lock();
  }

  /**
   * Perform tasks needed after the completion of snapshot operation.
   * @see #preSnapshotOperation()
   */
  public void postSnapshotOperation() {
    archiveLock.unlock();
  }

  /**
   * Closes and archives the compacted files under this store
   */
  public synchronized void closeAndArchiveCompactedFiles() throws IOException {
    // ensure other threads do not attempt to archive the same files on close()
    archiveLock.lock();
    try {
      lock.readLock().lock();
      Collection<HStoreFile> copyCompactedfiles = null;
      try {
        Collection<HStoreFile> compactedfiles =
            this.getStoreEngine().getStoreFileManager().getCompactedfiles();
        if (CollectionUtils.isNotEmpty(compactedfiles)) {
          // Do a copy under read lock
          copyCompactedfiles = new ArrayList<>(compactedfiles);
        } else {
          LOG.trace("No compacted files to archive");
        }
      } finally {
        lock.readLock().unlock();
      }
      if (CollectionUtils.isNotEmpty(copyCompactedfiles)) {
        removeCompactedfiles(copyCompactedfiles);
      }
    } finally {
      archiveLock.unlock();
    }
  }

  /**
   * Archives and removes the compacted files
   * @param compactedfiles The compacted files in this store that are not active in reads
   * @throws IOException
   */
  private void removeCompactedfiles(Collection<HStoreFile> compactedfiles)
      throws IOException {
    final List<HStoreFile> filesToRemove = new ArrayList<>(compactedfiles.size());
    for (final HStoreFile file : compactedfiles) {
      synchronized (file) {
        try {
          StoreFileReader r = file.getReader();
          if (r == null) {
            LOG.debug("The file {} was closed but still not archived", file);
            filesToRemove.add(file);
            continue;
          }
          if (file.isCompactedAway() && !file.isReferencedInReads()) {
            // Even if deleting fails we need not bother as any new scanners won't be
            // able to use the compacted file as the status is already compactedAway
            LOG.trace("Closing and archiving the file {}", file);
            r.close(true);
            // Just close and return
            filesToRemove.add(file);
          } else {
            LOG.info("Can't archive compacted file " + file.getPath()
                + " because of either isCompactedAway = " + file.isCompactedAway()
                + " or file has reference, isReferencedInReads = " + file.isReferencedInReads()
                + ", skipping for now.");
          }
        } catch (Exception e) {
          LOG.error("Exception while trying to close the compacted store file {}",
            file.getPath(), e);
        }
      }
    }
    if (this.isPrimaryReplicaStore()) {
      // Only the primary region is allowed to move the file to archive.
      // The secondary region does not move the files to archive. Any active reads from
      // the secondary region will still work because the file as such has active readers on it.
      if (!filesToRemove.isEmpty()) {
        LOG.debug("Moving the files {} to archive", filesToRemove);
        // Only if this is successful it has to be removed
        try {
          this.fs.removeStoreFiles(this.getColumnFamilyDescriptor().getNameAsString(), filesToRemove);
        } catch (FailedArchiveException fae) {
          // Even if archiving some files failed, we still need to clear out any of the
          // files which were successfully archived.  Otherwise we will receive a
          // FileNotFoundException when we attempt to re-archive them in the next go around.
          Collection<Path> failedFiles = fae.getFailedFiles();
          Iterator<HStoreFile> iter = filesToRemove.iterator();
          while (iter.hasNext()) {
            if (failedFiles.contains(iter.next().getPath())) {
              iter.remove();
            }
          }
          if (!filesToRemove.isEmpty()) {
            clearCompactedfiles(filesToRemove);
          }
          throw fae;
        }
      }
    }
    if (!filesToRemove.isEmpty()) {
      // Clear the compactedfiles from the store file manager
      clearCompactedfiles(filesToRemove);
    }
  }

  public Long preFlushSeqIDEstimation() {
    return memstore.preFlushSeqIDEstimation();
  }

  @Override
  public boolean isSloppyMemStore() {
    return this.memstore.isSloppy();
  }

  private void clearCompactedfiles(List<HStoreFile> filesToRemove) throws IOException {
    LOG.trace("Clearing the compacted file {} from this store", filesToRemove);
    try {
      lock.writeLock().lock();
      this.getStoreEngine().getStoreFileManager().removeCompactedFiles(filesToRemove);
    } finally {
      lock.writeLock().unlock();
    }
  }
}