/**
    *
    * 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.util.ArrayList;
  import java.util.Arrays;
  import java.util.Collection;
  import java.util.Collections;
  import java.util.Comparator;
  import java.util.HashMap;
  import java.util.Iterator;
  import java.util.List;
  import java.util.Map;
  import java.util.TreeMap;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.hadoop.conf.Configuration;
  import org.apache.hadoop.hbase.Cell;
  import org.apache.hadoop.hbase.HConstants;
  import org.apache.hadoop.hbase.KeyValue;
  import org.apache.hadoop.hbase.KeyValue.KVComparator;
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.hbase.regionserver.compactions.StripeCompactionPolicy;
  import org.apache.hadoop.hbase.util.Bytes;
  import org.apache.hadoop.hbase.util.ConcatenatedLists;
  import org.apache.hadoop.util.StringUtils.TraditionalBinaryPrefix;
  
  import com.google.common.collect.ImmutableCollection;
  import com.google.common.collect.ImmutableList;
  
  /**
   * Stripe implementation of StoreFileManager.
   * Not thread safe - relies on external locking (in HStore). Collections that this class
   * returns are immutable or unique to the call, so they should be safe.
   * Stripe store splits the key space of the region into non-overlapping stripes, as well as
   * some recent files that have all the keys (level 0). Each stripe contains a set of files.
   * When L0 is compacted, it's split into the files corresponding to existing stripe boundaries,
   * that can thus be added to stripes.
   * When scan or get happens, it only has to read the files from the corresponding stripes.
   * See StripeCompationPolicy on how the stripes are determined; this class doesn't care.
   *
   * This class should work together with StripeCompactionPolicy and StripeCompactor.
   * With regard to how they work, we make at least the following (reasonable) assumptions:
   *  - Compaction produces one file per new stripe (if any); that is easy to change.
   *  - Compaction has one contiguous set of stripes both in and out, except if L0 is involved.
   */
  @InterfaceAudience.Private
  public class StripeStoreFileManager
    implements StoreFileManager, StripeCompactionPolicy.StripeInformationProvider {
    private static final Log LOG = LogFactory.getLog(StripeStoreFileManager.class);
  
    /**
     * The file metadata fields that contain the stripe information.
     */
    public static final byte[] STRIPE_START_KEY = Bytes.toBytes("STRIPE_START_KEY");
    public static final byte[] STRIPE_END_KEY = Bytes.toBytes("STRIPE_END_KEY");
  
    private final static Bytes.RowEndKeyComparator MAP_COMPARATOR = new Bytes.RowEndKeyComparator();
  
    /**
     * The key value used for range boundary, indicating that the boundary is open (i.e. +-inf).
     */
    public final static byte[] OPEN_KEY = HConstants.EMPTY_BYTE_ARRAY;
    final static byte[] INVALID_KEY = null;
  
    /**
     * The state class. Used solely to replace results atomically during
     * compactions and avoid complicated error handling.
     */
    private static class State {
      /**
       * The end rows of each stripe. The last stripe end is always open-ended, so it's not stored
       * here. It is invariant that the start row of the stripe is the end row of the previous one
       * (and is an open boundary for the first one).
       */
      public byte[][] stripeEndRows = new byte[0][];
  
      /**
       * Files by stripe. Each element of the list corresponds to stripeEndRow element with the
       * same index, except the last one. Inside each list, the files are in reverse order by
       * seqNum. Note that the length of this is one higher than that of stripeEndKeys.
      */
     public ArrayList<ImmutableList<StoreFile>> stripeFiles
       = new ArrayList<ImmutableList<StoreFile>>();
     /** Level 0. The files are in reverse order by seqNum. */
     public ImmutableList<StoreFile> level0Files = ImmutableList.<StoreFile>of();
 
     /** Cached list of all files in the structure, to return from some calls */
     public ImmutableList<StoreFile> allFilesCached = ImmutableList.<StoreFile>of();
     private ImmutableList<StoreFile> allCompactedFilesCached = ImmutableList.<StoreFile>of();
   }
   private State state = null;
 
   /** Cached file metadata (or overrides as the case may be) */
   private HashMap<StoreFile, byte[]> fileStarts = new HashMap<StoreFile, byte[]>();
   private HashMap<StoreFile, byte[]> fileEnds = new HashMap<StoreFile, byte[]>();
   /** Normally invalid key is null, but in the map null is the result for "no key"; so use
    * the following constant value in these maps instead. Note that this is a constant and
    * we use it to compare by reference when we read from the map. */
   private static final byte[] INVALID_KEY_IN_MAP = new byte[0];
 
   private final KVComparator kvComparator;
   private StripeStoreConfig config;
 
   private final int blockingFileCount;
 
   public StripeStoreFileManager(
       KVComparator kvComparator, Configuration conf, StripeStoreConfig config) {
     this.kvComparator = kvComparator;
     this.config = config;
     this.blockingFileCount = conf.getInt(
         HStore.BLOCKING_STOREFILES_KEY, HStore.DEFAULT_BLOCKING_STOREFILE_COUNT);
   }
 
   @Override
   public void loadFiles(List<StoreFile> storeFiles) {
     loadUnclassifiedStoreFiles(storeFiles);
   }
 
   @Override
   public Collection<StoreFile> getStorefiles() {
     return state.allFilesCached;
   }
 
   @Override
   public Collection<StoreFile> getCompactedfiles() {
     return state.allCompactedFilesCached;
   }
 
   @Override
   public void insertNewFiles(Collection<StoreFile> sfs) throws IOException {
     CompactionOrFlushMergeCopy cmc = new CompactionOrFlushMergeCopy(true);
     // Passing null does not cause NPE??
     cmc.mergeResults(null, sfs);
     debugDumpState("Added new files");
   }
 
   @Override
   public ImmutableCollection<StoreFile> clearFiles() {
     ImmutableCollection<StoreFile> result = state.allFilesCached;
     this.state = new State();
     this.fileStarts.clear();
     this.fileEnds.clear();
     return result;
   }
 
   @Override
   public ImmutableCollection<StoreFile> clearCompactedFiles() {
     ImmutableCollection<StoreFile> result = state.allCompactedFilesCached;
     this.state = new State();
     return result;
   }
 
   @Override
   public int getStorefileCount() {
     return state.allFilesCached.size();
   }
 
   /** See {@link StoreFileManager#getCandidateFilesForRowKeyBefore(KeyValue)}
    * for details on this methods. */
   @Override
   public Iterator<StoreFile> getCandidateFilesForRowKeyBefore(final KeyValue targetKey) {
     KeyBeforeConcatenatedLists result = new KeyBeforeConcatenatedLists();
     // Order matters for this call.
     result.addSublist(state.level0Files);
     if (!state.stripeFiles.isEmpty()) {
       int lastStripeIndex = findStripeForRow(targetKey.getRow(), false);
       for (int stripeIndex = lastStripeIndex; stripeIndex >= 0; --stripeIndex) {
         result.addSublist(state.stripeFiles.get(stripeIndex));
       }
     }
     return result.iterator();
   }
 
   /** See {@link StoreFileManager#getCandidateFilesForRowKeyBefore(KeyValue)} and
    * {@link StoreFileManager#updateCandidateFilesForRowKeyBefore(Iterator, KeyValue, Cell)}
    * for details on this methods. */
   @Override
   public Iterator<StoreFile> updateCandidateFilesForRowKeyBefore(
       Iterator<StoreFile> candidateFiles, final KeyValue targetKey, final Cell candidate) {
     KeyBeforeConcatenatedLists.Iterator original =
         (KeyBeforeConcatenatedLists.Iterator)candidateFiles;
     assert original != null;
     ArrayList<List<StoreFile>> components = original.getComponents();
     for (int firstIrrelevant = 0; firstIrrelevant < components.size(); ++firstIrrelevant) {
       StoreFile sf = components.get(firstIrrelevant).get(0);
       byte[] endKey = endOf(sf);
       // Entries are ordered as such: L0, then stripes in reverse order. We never remove
       // level 0; we remove the stripe, and all subsequent ones, as soon as we find the
       // first one that cannot possibly have better candidates.
       if (!isInvalid(endKey) && !isOpen(endKey)
           && (nonOpenRowCompare(endKey, targetKey.getRow()) <= 0)) {
         original.removeComponents(firstIrrelevant);
         break;
       }
     }
     return original;
   }
 
   @Override
   /**
    * Override of getSplitPoint that determines the split point as the boundary between two
    * stripes, unless it causes significant imbalance between split sides' sizes. In that
    * case, the split boundary will be chosen from the middle of one of the stripes to
    * minimize imbalance.
    * @return The split point, or null if no split is possible.
    */
   public byte[] getSplitPoint() throws IOException {
     if (this.getStorefileCount() == 0) return null;
     if (state.stripeFiles.size() <= 1) {
       return getSplitPointFromAllFiles();
     }
     int leftIndex = -1, rightIndex = state.stripeFiles.size();
     long leftSize = 0, rightSize = 0;
     long lastLeftSize = 0, lastRightSize = 0;
     while (rightIndex - 1 != leftIndex) {
       if (leftSize >= rightSize) {
         --rightIndex;
         lastRightSize = getStripeFilesSize(rightIndex);
         rightSize += lastRightSize;
       } else {
         ++leftIndex;
         lastLeftSize = getStripeFilesSize(leftIndex);
         leftSize += lastLeftSize;
       }
     }
     if (leftSize == 0 || rightSize == 0) {
       String errMsg = String.format("Cannot split on a boundary - left index %d size %d, "
           + "right index %d size %d", leftIndex, leftSize, rightIndex, rightSize);
       debugDumpState(errMsg);
       LOG.warn(errMsg);
       return getSplitPointFromAllFiles();
     }
     double ratio = (double)rightSize / leftSize;
     if (ratio < 1) {
       ratio = 1 / ratio;
     }
     if (config.getMaxSplitImbalance() > ratio) return state.stripeEndRows[leftIndex];
 
     // If the difference between the sides is too large, we could get the proportional key on
     // the a stripe to equalize the difference, but there's no proportional key method at the
     // moment, and it's not extremely important.
     // See if we can achieve better ratio if we split the bigger side in half.
     boolean isRightLarger = rightSize >= leftSize;
     double newRatio = isRightLarger
         ? getMidStripeSplitRatio(leftSize, rightSize, lastRightSize)
         : getMidStripeSplitRatio(rightSize, leftSize, lastLeftSize);
     if (newRatio < 1) {
       newRatio = 1 / newRatio;
     }
     if (newRatio >= ratio)  return state.stripeEndRows[leftIndex];
     LOG.debug("Splitting the stripe - ratio w/o split " + ratio + ", ratio with split "
         + newRatio + " configured ratio " + config.getMaxSplitImbalance());
     // Ok, we may get better ratio, get it.
     return StoreUtils.getLargestFile(state.stripeFiles.get(
         isRightLarger ? rightIndex : leftIndex)).getFileSplitPoint(this.kvComparator);
   }
 
   private byte[] getSplitPointFromAllFiles() throws IOException {
     ConcatenatedLists<StoreFile> sfs = new ConcatenatedLists<StoreFile>();
     sfs.addSublist(state.level0Files);
     sfs.addAllSublists(state.stripeFiles);
     if (sfs.isEmpty()) return null;
     return StoreUtils.getLargestFile(sfs).getFileSplitPoint(this.kvComparator);
   }
 
   private double getMidStripeSplitRatio(long smallerSize, long largerSize, long lastLargerSize) {
     return (double)(largerSize - lastLargerSize / 2f) / (smallerSize + lastLargerSize / 2f);
   }
 
   @Override
   public Collection<StoreFile> getFilesForScanOrGet(byte[] startRow, boolean includeStartRow,
       byte[] stopRow, boolean includeStopRow) {
     if (state.stripeFiles.isEmpty()) {
       return state.level0Files; // There's just L0.
     }
 
     int firstStripe = findStripeForRow(startRow, true);
     int lastStripe = findStripeForRow(stopRow, false);
     assert firstStripe <= lastStripe;
     if (firstStripe == lastStripe && state.level0Files.isEmpty()) {
       return state.stripeFiles.get(firstStripe); // There's just one stripe we need.
     }
     if (firstStripe == 0 && lastStripe == (state.stripeFiles.size() - 1)) {
       return state.allFilesCached; // We need to read all files.
     }
 
     ConcatenatedLists<StoreFile> result = new ConcatenatedLists<StoreFile>();
     result.addAllSublists(state.stripeFiles.subList(firstStripe, lastStripe + 1));
     result.addSublist(state.level0Files);
     return result;
   }
 
   @Override
   public void addCompactionResults(
     Collection<StoreFile> compactedFiles, Collection<StoreFile> results) throws IOException {
     // See class comment for the assumptions we make here.
     LOG.debug("Attempting to merge compaction results: " + compactedFiles.size()
         + " files replaced by " + results.size());
     // In order to be able to fail in the middle of the operation, we'll operate on lazy
     // copies and apply the result at the end.
     CompactionOrFlushMergeCopy cmc = new CompactionOrFlushMergeCopy(false);
     cmc.mergeResults(compactedFiles, results);
     markCompactedAway(compactedFiles);
     debugDumpState("Merged compaction results");
   }
 
   // Mark the files as compactedAway once the storefiles and compactedfiles list is finalised
   // Let a background thread close the actual reader on these compacted files and also
   // ensure to evict the blocks from block cache so that they are no longer in
   // cache
   private void markCompactedAway(Collection<StoreFile> compactedFiles) {
     for (StoreFile file : compactedFiles) {
       file.markCompactedAway();
     }
   }
 
   @Override
   public void removeCompactedFiles(Collection<StoreFile> compactedFiles) throws IOException {
     // See class comment for the assumptions we make here.
     LOG.debug("Attempting to delete compaction results: " + compactedFiles.size());
     // In order to be able to fail in the middle of the operation, we'll operate on lazy
     // copies and apply the result at the end.
     CompactionOrFlushMergeCopy cmc = new CompactionOrFlushMergeCopy(false);
     cmc.deleteResults(compactedFiles);
     debugDumpState("Deleted compaction results");
   }
 
   @Override
   public int getStoreCompactionPriority() {
     // If there's only L0, do what the default store does.
     // If we are in critical priority, do the same - we don't want to trump all stores all
     // the time due to how many files we have.
     int fc = getStorefileCount();
     if (state.stripeFiles.isEmpty() || (this.blockingFileCount <= fc)) {
       return this.blockingFileCount - fc;
     }
     // If we are in good shape, we don't want to be trumped by all other stores due to how
     // many files we have, so do an approximate mapping to normal priority range; L0 counts
     // for all stripes.
     int l0 = state.level0Files.size(), sc = state.stripeFiles.size();
     int priority = (int)Math.ceil(((double)(this.blockingFileCount - fc + l0) / sc) - l0);
     return (priority <= HStore.PRIORITY_USER) ? (HStore.PRIORITY_USER + 1) : priority;
   }
 
   /**
    * Gets the total size of all files in the stripe.
    * @param stripeIndex Stripe index.
    * @return Size.
    */
   private long getStripeFilesSize(int stripeIndex) {
     long result = 0;
     for (StoreFile sf : state.stripeFiles.get(stripeIndex)) {
       result += sf.getReader().length();
     }
     return result;
   }
 
   /**
    * Loads initial store files that were picked up from some physical location pertaining to
    * this store (presumably). Unlike adding files after compaction, assumes empty initial
    * sets, and is forgiving with regard to stripe constraints - at worst, many/all files will
    * go to level 0.
    * @param storeFiles Store files to add.
    */
   private void loadUnclassifiedStoreFiles(List<StoreFile> storeFiles) {
     LOG.debug("Attempting to load " + storeFiles.size() + " store files.");
     TreeMap<byte[], ArrayList<StoreFile>> candidateStripes =
         new TreeMap<byte[], ArrayList<StoreFile>>(MAP_COMPARATOR);
     ArrayList<StoreFile> level0Files = new ArrayList<StoreFile>();
     // Separate the files into tentative stripes; then validate. Currently, we rely on metadata.
     // If needed, we could dynamically determine the stripes in future.
     for (StoreFile sf : storeFiles) {
       byte[] startRow = startOf(sf), endRow = endOf(sf);
       // Validate the range and put the files into place.
       if (isInvalid(startRow) || isInvalid(endRow)) {
         insertFileIntoStripe(level0Files, sf); // No metadata - goes to L0.
         ensureLevel0Metadata(sf);
       } else if (!isOpen(startRow) && !isOpen(endRow) &&
           nonOpenRowCompare(startRow, endRow) >= 0) {
         LOG.error("Unexpected metadata - start row [" + Bytes.toString(startRow) + "], end row ["
           + Bytes.toString(endRow) + "] in file [" + sf.getPath() + "], pushing to L0");
         insertFileIntoStripe(level0Files, sf); // Bad metadata - goes to L0 also.
         ensureLevel0Metadata(sf);
       } else {
         ArrayList<StoreFile> stripe = candidateStripes.get(endRow);
         if (stripe == null) {
           stripe = new ArrayList<StoreFile>();
           candidateStripes.put(endRow, stripe);
         }
         insertFileIntoStripe(stripe, sf);
       }
     }
     // Possible improvement - for variable-count stripes, if all the files are in L0, we can
     // instead create single, open-ended stripe with all files.
 
     boolean hasOverlaps = false;
     byte[] expectedStartRow = null; // first stripe can start wherever
     Iterator<Map.Entry<byte[], ArrayList<StoreFile>>> entryIter =
         candidateStripes.entrySet().iterator();
     while (entryIter.hasNext()) {
       Map.Entry<byte[], ArrayList<StoreFile>> entry = entryIter.next();
       ArrayList<StoreFile> files = entry.getValue();
       // Validate the file start rows, and remove the bad ones to level 0.
       for (int i = 0; i < files.size(); ++i) {
         StoreFile sf = files.get(i);
         byte[] startRow = startOf(sf);
         if (expectedStartRow == null) {
           expectedStartRow = startRow; // ensure that first stripe is still consistent
         } else if (!rowEquals(expectedStartRow, startRow)) {
           hasOverlaps = true;
           LOG.warn("Store file doesn't fit into the tentative stripes - expected to start at ["
               + Bytes.toString(expectedStartRow) + "], but starts at [" + Bytes.toString(startRow)
               + "], to L0 it goes");
           StoreFile badSf = files.remove(i);
           insertFileIntoStripe(level0Files, badSf);
           ensureLevel0Metadata(badSf);
           --i;
         }
       }
       // Check if any files from the candidate stripe are valid. If so, add a stripe.
       byte[] endRow = entry.getKey();
       if (!files.isEmpty()) {
         expectedStartRow = endRow; // Next stripe must start exactly at that key.
       } else {
         entryIter.remove();
       }
     }
 
     // In the end, there must be open ends on two sides. If not, and there were no errors i.e.
     // files are consistent, they might be coming from a split. We will treat the boundaries
     // as open keys anyway, and log the message.
     // If there were errors, we'll play it safe and dump everything into L0.
     if (!candidateStripes.isEmpty()) {
       StoreFile firstFile = candidateStripes.firstEntry().getValue().get(0);
       boolean isOpen = isOpen(startOf(firstFile)) && isOpen(candidateStripes.lastKey());
       if (!isOpen) {
         LOG.warn("The range of the loaded files does not cover full key space: from ["
             + Bytes.toString(startOf(firstFile)) + "], to ["
             + Bytes.toString(candidateStripes.lastKey()) + "]");
         if (!hasOverlaps) {
           ensureEdgeStripeMetadata(candidateStripes.firstEntry().getValue(), true);
           ensureEdgeStripeMetadata(candidateStripes.lastEntry().getValue(), false);
         } else {
           LOG.warn("Inconsistent files, everything goes to L0.");
           for (ArrayList<StoreFile> files : candidateStripes.values()) {
             for (StoreFile sf : files) {
               insertFileIntoStripe(level0Files, sf);
               ensureLevel0Metadata(sf);
             }
           }
           candidateStripes.clear();
         }
       }
     }
 
     // Copy the results into the fields.
     State state = new State();
     state.level0Files = ImmutableList.copyOf(level0Files);
     state.stripeFiles = new ArrayList<ImmutableList<StoreFile>>(candidateStripes.size());
     state.stripeEndRows = new byte[Math.max(0, candidateStripes.size() - 1)][];
     ArrayList<StoreFile> newAllFiles = new ArrayList<StoreFile>(level0Files);
     int i = candidateStripes.size() - 1;
     for (Map.Entry<byte[], ArrayList<StoreFile>> entry : candidateStripes.entrySet()) {
       state.stripeFiles.add(ImmutableList.copyOf(entry.getValue()));
       newAllFiles.addAll(entry.getValue());
       if (i > 0) {
         state.stripeEndRows[state.stripeFiles.size() - 1] = entry.getKey();
       }
       --i;
     }
     state.allFilesCached = ImmutableList.copyOf(newAllFiles);
     this.state = state;
     debugDumpState("Files loaded");
   }
 
   private void ensureEdgeStripeMetadata(ArrayList<StoreFile> stripe, boolean isFirst) {
     HashMap<StoreFile, byte[]> targetMap = isFirst ? fileStarts : fileEnds;
     for (StoreFile sf : stripe) {
       targetMap.put(sf, OPEN_KEY);
     }
   }
 
   private void ensureLevel0Metadata(StoreFile sf) {
     if (!isInvalid(startOf(sf))) this.fileStarts.put(sf, INVALID_KEY_IN_MAP);
     if (!isInvalid(endOf(sf))) this.fileEnds.put(sf, INVALID_KEY_IN_MAP);
   }
 
   private void debugDumpState(String string) {
     if (!LOG.isDebugEnabled()) return;
     StringBuilder sb = new StringBuilder();
     sb.append("\n" + string + "; current stripe state is as such:");
     sb.append("\n level 0 with ")
         .append(state.level0Files.size())
         .append(
           " files: "
               + TraditionalBinaryPrefix.long2String(
                 StripeCompactionPolicy.getTotalFileSize(state.level0Files), "", 1) + ";");
     for (int i = 0; i < state.stripeFiles.size(); ++i) {
       String endRow = (i == state.stripeEndRows.length)
           ? "(end)" : "[" + Bytes.toString(state.stripeEndRows[i]) + "]";
       sb.append("\n stripe ending in ")
           .append(endRow)
           .append(" with ")
           .append(state.stripeFiles.get(i).size())
           .append(
             " files: "
                 + TraditionalBinaryPrefix.long2String(
                   StripeCompactionPolicy.getTotalFileSize(state.stripeFiles.get(i)), "", 1) + ";");
     }
     sb.append("\n").append(state.stripeFiles.size()).append(" stripes total.");
     sb.append("\n").append(getStorefileCount()).append(" files total.");
     LOG.debug(sb.toString());
   }
 
   /**
    * Checks whether the key indicates an open interval boundary (i.e. infinity).
    */
   private static final boolean isOpen(byte[] key) {
     return key != null && key.length == 0;
   }
 
   /**
    * Checks whether the key is invalid (e.g. from an L0 file, or non-stripe-compacted files).
    */
   private static final boolean isInvalid(byte[] key) {
     return key == INVALID_KEY;
   }
 
   /**
    * Compare two keys for equality.
    */
   private final boolean rowEquals(byte[] k1, byte[] k2) {
     return kvComparator.matchingRows(k1, 0, k1.length, k2, 0, k2.length);
   }
 
   /**
    * Compare two keys. Keys must not be open (isOpen(row) == false).
    */
   private final int nonOpenRowCompare(byte[] k1, byte[] k2) {
     assert !isOpen(k1) && !isOpen(k2);
     return kvComparator.compareRows(k1, 0, k1.length, k2, 0, k2.length);
   }
 
   /**
    * Finds the stripe index by end row.
    */
   private final int findStripeIndexByEndRow(byte[] endRow) {
     assert !isInvalid(endRow);
     if (isOpen(endRow)) return state.stripeEndRows.length;
     return Arrays.binarySearch(state.stripeEndRows, endRow, Bytes.BYTES_COMPARATOR);
   }
 
   /**
    * Finds the stripe index for the stripe containing a row provided externally for get/scan.
    */
   private final int findStripeForRow(byte[] row, boolean isStart) {
     if (isStart && row == HConstants.EMPTY_START_ROW) return 0;
     if (!isStart && row == HConstants.EMPTY_END_ROW) return state.stripeFiles.size() - 1;
     // If there's an exact match below, a stripe ends at "row". Stripe right boundary is
     // exclusive, so that means the row is in the next stripe; thus, we need to add one to index.
     // If there's no match, the return value of binarySearch is (-(insertion point) - 1), where
     // insertion point is the index of the next greater element, or list size if none. The
     // insertion point happens to be exactly what we need, so we need to add one to the result.
     return Math.abs(Arrays.binarySearch(state.stripeEndRows, row, Bytes.BYTES_COMPARATOR) + 1);
   }
 
   @Override
   public final byte[] getStartRow(int stripeIndex) {
     return (stripeIndex == 0  ? OPEN_KEY : state.stripeEndRows[stripeIndex - 1]);
   }
 
   @Override
   public final byte[] getEndRow(int stripeIndex) {
     return (stripeIndex == state.stripeEndRows.length
         ? OPEN_KEY : state.stripeEndRows[stripeIndex]);
   }
 
 
   private byte[] startOf(StoreFile sf) {
     byte[] result = this.fileStarts.get(sf);
     return result == null ? sf.getMetadataValue(STRIPE_START_KEY)
         : (result == INVALID_KEY_IN_MAP ? INVALID_KEY : result);
   }
 
   private byte[] endOf(StoreFile sf) {
     byte[] result = this.fileEnds.get(sf);
     return result == null ? sf.getMetadataValue(STRIPE_END_KEY)
         : (result == INVALID_KEY_IN_MAP ? INVALID_KEY : result);
   }
 
   /**
    * Inserts a file in the correct place (by seqnum) in a stripe copy.
    * @param stripe Stripe copy to insert into.
    * @param sf File to insert.
    */
   private static void insertFileIntoStripe(ArrayList<StoreFile> stripe, StoreFile sf) {
     // The only operation for which sorting of the files matters is KeyBefore. Therefore,
     // we will store the file in reverse order by seqNum from the outset.
     for (int insertBefore = 0; ; ++insertBefore) {
       if (insertBefore == stripe.size()
           || (StoreFile.Comparators.SEQ_ID.compare(sf, stripe.get(insertBefore)) >= 0)) {
         stripe.add(insertBefore, sf);
         break;
       }
     }
   }
 
   /**
    * An extension of ConcatenatedLists that has several peculiar properties.
    * First, one can cut the tail of the logical list by removing last several sub-lists.
    * Second, items can be removed thru iterator.
    * Third, if the sub-lists are immutable, they are replaced with mutable copies when needed.
    * On average KeyBefore operation will contain half the stripes as potential candidates,
    * but will quickly cut down on them as it finds something in the more likely ones; thus,
    * the above allow us to avoid unnecessary copying of a bunch of lists.
    */
   private static class KeyBeforeConcatenatedLists extends ConcatenatedLists<StoreFile> {
     @Override
     public java.util.Iterator<StoreFile> iterator() {
       return new Iterator();
     }
 
     public class Iterator extends ConcatenatedLists<StoreFile>.Iterator {
       public ArrayList<List<StoreFile>> getComponents() {
         return components;
       }
 
       public void removeComponents(int startIndex) {
         List<List<StoreFile>> subList = components.subList(startIndex, components.size());
         for (List<StoreFile> entry : subList) {
           size -= entry.size();
         }
         assert size >= 0;
         subList.clear();
       }
 
       @Override
       public void remove() {
         if (!this.nextWasCalled) {
           throw new IllegalStateException("No element to remove");
         }
         this.nextWasCalled = false;
         List<StoreFile> src = components.get(currentComponent);
         if (src instanceof ImmutableList<?>) {
           src = new ArrayList<StoreFile>(src);
           components.set(currentComponent, src);
         }
         src.remove(indexWithinComponent);
         --size;
         --indexWithinComponent;
         if (src.isEmpty()) {
           components.remove(currentComponent); // indexWithinComponent is already -1 here.
         }
       }
     }
   }
 
   /**
    * Non-static helper class for merging compaction or flush results.
    * Since we want to merge them atomically (more or less), it operates on lazy copies,
    * then creates a new state object and puts it in place.
    */
   private class CompactionOrFlushMergeCopy {
     private ArrayList<List<StoreFile>> stripeFiles = null;
     private ArrayList<StoreFile> level0Files = null;
     private ArrayList<byte[]> stripeEndRows = null;
 
     private Collection<StoreFile> compactedFiles = null;
     private Collection<StoreFile> results = null;
 
     private List<StoreFile> l0Results = new ArrayList<StoreFile>();
     private final boolean isFlush;
 
     public CompactionOrFlushMergeCopy(boolean isFlush) {
       // Create a lazy mutable copy (other fields are so lazy they start out as nulls).
       this.stripeFiles = new ArrayList<List<StoreFile>>(
           StripeStoreFileManager.this.state.stripeFiles);
       this.isFlush = isFlush;
     }
 
     private void mergeResults(Collection<StoreFile> compactedFiles, Collection<StoreFile> results)
         throws IOException {
       assert this.compactedFiles == null && this.results == null;
       this.compactedFiles = compactedFiles;
       this.results = results;
       // Do logical processing.
       if (!isFlush) removeCompactedFiles();
       TreeMap<byte[], StoreFile> newStripes = processResults();
       if (newStripes != null) {
         processNewCandidateStripes(newStripes);
       }
       // Create new state and update parent.
       State state = createNewState(false);
       StripeStoreFileManager.this.state = state;
       updateMetadataMaps();
     }
 
     private void deleteResults(Collection<StoreFile> compactedFiles) throws IOException {
       this.compactedFiles = compactedFiles;
       // Create new state and update parent.
       State state = createNewState(true);
       StripeStoreFileManager.this.state = state;
       updateMetadataMaps();
     }
 
     private State createNewState(boolean delCompactedFiles) {
       State oldState = StripeStoreFileManager.this.state;
       // Stripe count should be the same unless the end rows changed.
       assert oldState.stripeFiles.size() == this.stripeFiles.size() || this.stripeEndRows != null;
       State newState = new State();
       newState.level0Files = (this.level0Files == null) ? oldState.level0Files
           : ImmutableList.copyOf(this.level0Files);
       newState.stripeEndRows = (this.stripeEndRows == null) ? oldState.stripeEndRows
           : this.stripeEndRows.toArray(new byte[this.stripeEndRows.size()][]);
       newState.stripeFiles = new ArrayList<ImmutableList<StoreFile>>(this.stripeFiles.size());
       for (List<StoreFile> newStripe : this.stripeFiles) {
         newState.stripeFiles.add(newStripe instanceof ImmutableList<?>
             ? (ImmutableList<StoreFile>)newStripe : ImmutableList.copyOf(newStripe));
       }
 
       List<StoreFile> newAllFiles = new ArrayList<StoreFile>(oldState.allFilesCached);
       List<StoreFile> newAllCompactedFiles =
           new ArrayList<StoreFile>(oldState.allCompactedFilesCached);
       if (!isFlush) {
         newAllFiles.removeAll(compactedFiles);
         if (delCompactedFiles) {
           newAllCompactedFiles.removeAll(compactedFiles);
         } else {
           newAllCompactedFiles.addAll(compactedFiles);
         }
       }
       if (results != null) {
         newAllFiles.addAll(results);
       }
       newState.allFilesCached = ImmutableList.copyOf(newAllFiles);
       newState.allCompactedFilesCached = ImmutableList.copyOf(newAllCompactedFiles);
       return newState;
     }
 
     private void updateMetadataMaps() {
       StripeStoreFileManager parent = StripeStoreFileManager.this;
       if (!isFlush) {
         for (StoreFile sf : this.compactedFiles) {
           parent.fileStarts.remove(sf);
           parent.fileEnds.remove(sf);
         }
       }
       if (this.l0Results != null) {
         for (StoreFile sf : this.l0Results) {
           parent.ensureLevel0Metadata(sf);
         }
       }
     }
 
     /**
      * @param index Index of the stripe we need.
      * @return A lazy stripe copy from current stripes.
      */
     private final ArrayList<StoreFile> getStripeCopy(int index) {
       List<StoreFile> stripeCopy = this.stripeFiles.get(index);
       ArrayList<StoreFile> result = null;
       if (stripeCopy instanceof ImmutableList<?>) {
         result = new ArrayList<StoreFile>(stripeCopy);
         this.stripeFiles.set(index, result);
       } else {
         result = (ArrayList<StoreFile>)stripeCopy;
       }
       return result;
     }
 
     /**
      * @return A lazy L0 copy from current state.
      */
     private final ArrayList<StoreFile> getLevel0Copy() {
       if (this.level0Files == null) {
         this.level0Files = new ArrayList<StoreFile>(StripeStoreFileManager.this.state.level0Files);
       }
       return this.level0Files;
     }
 
     /**
      * Process new files, and add them either to the structure of existing stripes,
      * or to the list of new candidate stripes.
      * @return New candidate stripes.
      */
     private TreeMap<byte[], StoreFile> processResults() throws IOException {
       TreeMap<byte[], StoreFile> newStripes = null;
       for (StoreFile sf : this.results) {
         byte[] startRow = startOf(sf), endRow = endOf(sf);
         if (isInvalid(endRow) || isInvalid(startRow)) {
           if (!isFlush) {
             LOG.warn("The newly compacted file doesn't have stripes set: " + sf.getPath());
           }
           insertFileIntoStripe(getLevel0Copy(), sf);
           this.l0Results.add(sf);
           continue;
         }
         if (!this.stripeFiles.isEmpty()) {
           int stripeIndex = findStripeIndexByEndRow(endRow);
           if ((stripeIndex >= 0) && rowEquals(getStartRow(stripeIndex), startRow)) {
             // Simple/common case - add file to an existing stripe.
             insertFileIntoStripe(getStripeCopy(stripeIndex), sf);
             continue;
           }
         }
 
         // Make a new candidate stripe.
         if (newStripes == null) {
           newStripes = new TreeMap<byte[], StoreFile>(MAP_COMPARATOR);
         }
         StoreFile oldSf = newStripes.put(endRow, sf);
         if (oldSf != null) {
           throw new IOException("Compactor has produced multiple files for the stripe ending in ["
               + Bytes.toString(endRow) + "], found " + sf.getPath() + " and " + oldSf.getPath());
         }
       }
       return newStripes;
     }
 
     /**
      * Remove compacted files.
      */
     private void removeCompactedFiles() throws IOException {
       for (StoreFile oldFile : this.compactedFiles) {
         byte[] oldEndRow = endOf(oldFile);
         List<StoreFile> source = null;
         if (isInvalid(oldEndRow)) {
           source = getLevel0Copy();
         } else {
           int stripeIndex = findStripeIndexByEndRow(oldEndRow);
           if (stripeIndex < 0) {
             throw new IOException("An allegedly compacted file [" + oldFile + "] does not belong"
                 + " to a known stripe (end row - [" + Bytes.toString(oldEndRow) + "])");
           }
           source = getStripeCopy(stripeIndex);
         }
         if (!source.remove(oldFile)) {
           throw new IOException("An allegedly compacted file [" + oldFile + "] was not found");
         }
       }
     }
 
     /**
      * See {@link #addCompactionResults(Collection, Collection)} - updates the stripe list with
      * new candidate stripes/removes old stripes; produces new set of stripe end rows.
      * @param newStripes  New stripes - files by end row.
      */
     private void processNewCandidateStripes(
         TreeMap<byte[], StoreFile> newStripes) throws IOException {
       // Validate that the removed and added aggregate ranges still make for a full key space.
       boolean hasStripes = !this.stripeFiles.isEmpty();
       this.stripeEndRows = new ArrayList<byte[]>(
           Arrays.asList(StripeStoreFileManager.this.state.stripeEndRows));
       int removeFrom = 0;
       byte[] firstStartRow = startOf(newStripes.firstEntry().getValue());
       byte[] lastEndRow = newStripes.lastKey();
       if (!hasStripes && (!isOpen(firstStartRow) || !isOpen(lastEndRow))) {
         throw new IOException("Newly created stripes do not cover the entire key space.");
       }
 
       boolean canAddNewStripes = true;
       Collection<StoreFile> filesForL0 = null;
       if (hasStripes) {
         // Determine which stripes will need to be removed because they conflict with new stripes.
         // The new boundaries should match old stripe boundaries, so we should get exact matches.
         if (isOpen(firstStartRow)) {
           removeFrom = 0;
         } else {
           removeFrom = findStripeIndexByEndRow(firstStartRow);
           if (removeFrom < 0) throw new IOException("Compaction is trying to add a bad range.");
           ++removeFrom;
         }
         int removeTo = findStripeIndexByEndRow(lastEndRow);
         if (removeTo < 0) throw new IOException("Compaction is trying to add a bad range.");
         // See if there are files in the stripes we are trying to replace.
         ArrayList<StoreFile> conflictingFiles = new ArrayList<StoreFile>();
         for (int removeIndex = removeTo; removeIndex >= removeFrom; --removeIndex) {
           conflictingFiles.addAll(this.stripeFiles.get(removeIndex));
         }
         if (!conflictingFiles.isEmpty()) {
           // This can be caused by two things - concurrent flush into stripes, or a bug.
           // Unfortunately, we cannot tell them apart without looking at timing or something
           // like that. We will assume we are dealing with a flush and dump it into L0.
           if (isFlush) {
             long newSize = StripeCompactionPolicy.getTotalFileSize(newStripes.values());
             LOG.warn("Stripes were created by a flush, but results of size " + newSize
                 + " cannot be added because the stripes have changed");
             canAddNewStripes = false;
             filesForL0 = newStripes.values();
           } else {
             long oldSize = StripeCompactionPolicy.getTotalFileSize(conflictingFiles);
             LOG.info(conflictingFiles.size() + " conflicting files (likely created by a flush) "
                 + " of size " + oldSize + " are moved to L0 due to concurrent stripe change");
             filesForL0 = conflictingFiles;
           }
           if (filesForL0 != null) {
             for (StoreFile sf : filesForL0) {
               insertFileIntoStripe(getLevel0Copy(), sf);
             }
             l0Results.addAll(filesForL0);
           }
         }
 
         if (canAddNewStripes) {
           // Remove old empty stripes.
           int originalCount = this.stripeFiles.size();
           for (int removeIndex = removeTo; removeIndex >= removeFrom; --removeIndex) {
             if (removeIndex != originalCount - 1) {
               this.stripeEndRows.remove(removeIndex);
             }
             this.stripeFiles.remove(removeIndex);
           }
         }
       }
 
       if (!canAddNewStripes) return; // Files were already put into L0.
 
       // Now, insert new stripes. The total ranges match, so we can insert where we removed.
       byte[] previousEndRow = null;
       int insertAt = removeFrom;
       for (Map.Entry<byte[], StoreFile> newStripe : newStripes.entrySet()) {
         if (previousEndRow != null) {
           // Validate that the ranges are contiguous.
           assert !isOpen(previousEndRow);
           byte[] startRow = startOf(newStripe.getValue());
           if (!rowEquals(previousEndRow, startRow)) {
             throw new IOException("The new stripes produced by "
                 + (isFlush ? "flush" : "compaction") + " are not contiguous");
           }
         }
         // Add the new stripe.
         ArrayList<StoreFile> tmp = new ArrayList<StoreFile>();
         tmp.add(newStripe.getValue());
         stripeFiles.add(insertAt, tmp);
         previousEndRow = newStripe.getKey();
         if (!isOpen(previousEndRow)) {
           stripeEndRows.add(insertAt, previousEndRow);
         }
         ++insertAt;
       }
     }
   }
 
   @Override
   public List<StoreFile> getLevel0Files() {
     return this.state.level0Files;
   }
 
   @Override
   public List<byte[]> getStripeBoundaries() {
     if (this.state.stripeFiles.isEmpty()) return new ArrayList<byte[]>();
     ArrayList<byte[]> result = new ArrayList<byte[]>(this.state.stripeEndRows.length + 2);
     result.add(OPEN_KEY);
     Collections.addAll(result, this.state.stripeEndRows);
     result.add(OPEN_KEY);
     return result;
   }
 
   @Override
   public ArrayList<ImmutableList<StoreFile>> getStripes() {
     return this.state.stripeFiles;
   }
 
   @Override
   public int getStripeCount() {
     return this.state.stripeFiles.size();
   }
 
   @Override
   public Collection<StoreFile> getUnneededFiles(long maxTs, List<StoreFile> filesCompacting) {
     // 1) We can never get rid of the last file which has the maximum seqid in a stripe.
     // 2) Files that are not the latest can't become one due to (1), so the rest are fair game.
     State state = this.state;
     Collection<StoreFile> expiredStoreFiles = null;
     for (ImmutableList<StoreFile> stripe : state.stripeFiles) {
       expiredStoreFiles = findExpiredFiles(stripe, maxTs, filesCompacting, expiredStoreFiles);
     }
     return findExpiredFiles(state.level0Files, maxTs, filesCompacting, expiredStoreFiles);
   }
 
   private Collection<StoreFile> findExpiredFiles(ImmutableList<StoreFile> stripe, long maxTs,
       List<StoreFile> filesCompacting, Collection<StoreFile> expiredStoreFiles) {
     // Order by seqnum is reversed.
     for (int i = 1; i < stripe.size(); ++i) {
       StoreFile sf = stripe.get(i);
       synchronized (sf) {
         long fileTs = sf.getReader().getMaxTimestamp();
         if (fileTs < maxTs && !filesCompacting.contains(sf)) {
           LOG.info("Found an expired store file: " + sf.getPath() + " whose maxTimeStamp is "
               + fileTs + ", which is below " + maxTs);
           if (expiredStoreFiles == null) {
             expiredStoreFiles = new ArrayList<StoreFile>();
           }
           expiredStoreFiles.add(sf);
         }
       }
     }
     return expiredStoreFiles;
   }
 
   @Override
   public double getCompactionPressure() {
     State stateLocal = this.state;
     if (stateLocal.allFilesCached.size() > blockingFileCount) {
       // just a hit to tell others that we have reached the blocking file count.
       return 2.0;
     }
     if (stateLocal.stripeFiles.isEmpty()) {
       return 0.0;
     }
     int blockingFilePerStripe = blockingFileCount / stateLocal.stripeFiles.size();
     // do not calculate L0 separately because data will be moved to stripe quickly and in most cases
     // we flush data to stripe directly.
     int delta = stateLocal.level0Files.isEmpty() ? 0 : 1;
     double max = 0.0;
     for (ImmutableList<StoreFile> stripeFile : stateLocal.stripeFiles) {
       int stripeFileCount = stripeFile.size();
       double normCount =
           (double) (stripeFileCount + delta - config.getStripeCompactMinFiles())
               / (blockingFilePerStripe - config.getStripeCompactMinFiles());
       if (normCount >= 1.0) {
         // This could happen if stripe is not split evenly. Do not return values that larger than
         // 1.0 because we have not reached the blocking file count actually.
         return 1.0;
       }
       if (normCount > max) {
         max = normCount;
       }
     }
     return max;
   }
 
   @Override
   public Comparator<StoreFile> getStoreFileComparator() {
     return StoreFile.Comparators.SEQ_ID;
   }
 }