/**
    *
    * 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.compactions;
  
  import com.google.common.collect.Iterators;
  import com.google.common.collect.Lists;
  import com.google.common.collect.PeekingIterator;
  import com.google.common.math.LongMath;
  
  import java.io.IOException;
  import java.util.ArrayList;
  import java.util.Collection;
  import java.util.Collections;
  import java.util.List;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.hadoop.conf.Configuration;
  import org.apache.hadoop.hbase.HBaseInterfaceAudience;
  import org.apache.hadoop.hbase.HDFSBlocksDistribution;
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.hbase.regionserver.RSRpcServices;
  import org.apache.hadoop.hbase.regionserver.StoreConfigInformation;
  import org.apache.hadoop.hbase.regionserver.StoreFile;
  import org.apache.hadoop.hbase.regionserver.StoreUtils;
  import org.apache.hadoop.hbase.util.EnvironmentEdgeManager;
  import org.apache.hadoop.hbase.util.Pair;
  import org.apache.hadoop.hbase.util.ReflectionUtils;
  
  /**
   * HBASE-15181 This is a simple implementation of date-based tiered compaction similar to
   * Cassandra's for the following benefits:
   * <ol>
   * <li>Improve date-range-based scan by structuring store files in date-based tiered layout.</li>
   * <li>Reduce compaction overhead.</li>
   * <li>Improve TTL efficiency.</li>
   * </ol>
   * Perfect fit for the use cases that:
   * <ol>
   * <li>has mostly date-based data write and scan and a focus on the most recent data.</li>
   * </ol>
   * Out-of-order writes are handled gracefully. Time range overlapping among store files is tolerated
   * and the performance impact is minimized. Configuration can be set at hbase-site or overridden at
   * per-table or per-column-family level by hbase shell. Design spec is at
   * https://docs.google.com/document/d/1_AmlNb2N8Us1xICsTeGDLKIqL6T-oHoRLZ323MG_uy8/
   */
  @InterfaceAudience.LimitedPrivate(HBaseInterfaceAudience.CONFIG)
  public class DateTieredCompactionPolicy extends SortedCompactionPolicy {
  
    private static final Log LOG = LogFactory.getLog(DateTieredCompactionPolicy.class);
  
    private final RatioBasedCompactionPolicy compactionPolicyPerWindow;
  
    private final CompactionWindowFactory windowFactory;
  
    public DateTieredCompactionPolicy(Configuration conf, StoreConfigInformation storeConfigInfo)
        throws IOException {
      super(conf, storeConfigInfo);
      try {
        compactionPolicyPerWindow = ReflectionUtils.instantiateWithCustomCtor(
          comConf.getCompactionPolicyForDateTieredWindow(),
          new Class[] { Configuration.class, StoreConfigInformation.class },
          new Object[] { conf, storeConfigInfo });
      } catch (Exception e) {
        throw new IOException("Unable to load configured compaction policy '"
            + comConf.getCompactionPolicyForDateTieredWindow() + "'", e);
      }
      try {
        windowFactory = ReflectionUtils.instantiateWithCustomCtor(
          comConf.getDateTieredCompactionWindowFactory(),
          new Class[] { CompactionConfiguration.class }, new Object[] { comConf });
      } catch (Exception e) {
        throw new IOException("Unable to load configured window factory '"
            + comConf.getDateTieredCompactionWindowFactory() + "'", e);
      }
    }
  
    /**
     * Heuristics for guessing whether we need minor compaction.
     */
    @Override
    @InterfaceAudience.Private
    public boolean needsCompaction(final Collection<StoreFile> storeFiles,
       final List<StoreFile> filesCompacting) {
     ArrayList<StoreFile> candidates = new ArrayList<StoreFile>(storeFiles);
     try {
       return !selectMinorCompaction(candidates, false, true).getFiles().isEmpty();
     } catch (Exception e) {
       LOG.error("Can not check for compaction: ", e);
       return false;
     }
   }
 
   public boolean shouldPerformMajorCompaction(final Collection<StoreFile> filesToCompact)
     throws IOException {
     long mcTime = getNextMajorCompactTime(filesToCompact);
     if (filesToCompact == null || mcTime == 0) {
       if (LOG.isDebugEnabled()) {
         LOG.debug("filesToCompact: " + filesToCompact + " mcTime: " + mcTime);
       }
       return false;
     }
 
     // TODO: Use better method for determining stamp of last major (HBASE-2990)
     long lowTimestamp = StoreUtils.getLowestTimestamp(filesToCompact);
     long now = EnvironmentEdgeManager.currentTime();
     if (lowTimestamp <= 0L || lowTimestamp >= (now - mcTime)) {
       if (LOG.isDebugEnabled()) {
         LOG.debug("lowTimestamp: " + lowTimestamp + " lowTimestamp: " + lowTimestamp + " now: " +
             now + " mcTime: " + mcTime); 
       }
       return false;
     }
 
     long cfTTL = this.storeConfigInfo.getStoreFileTtl();
     HDFSBlocksDistribution hdfsBlocksDistribution = new HDFSBlocksDistribution();
     List<Long> boundaries = getCompactBoundariesForMajor(filesToCompact, now);
     boolean[] filesInWindow = new boolean[boundaries.size()];
 
     for (StoreFile file: filesToCompact) {
       Long minTimestamp = file.getMinimumTimestamp();
       long oldest = (minTimestamp == null) ? Long.MIN_VALUE : now - minTimestamp.longValue();
       if (cfTTL != Long.MAX_VALUE && oldest >= cfTTL) {
         LOG.debug("Major compaction triggered on store " + this
           + "; for TTL maintenance");
         return true;
       }
       if (!file.isMajorCompaction() || file.isBulkLoadResult()) {
         LOG.debug("Major compaction triggered on store " + this
           + ", because there are new files and time since last major compaction "
           + (now - lowTimestamp) + "ms");
         return true;
       }
 
       int lowerWindowIndex = Collections.binarySearch(boundaries,
         minTimestamp == null ? (Long)Long.MAX_VALUE : minTimestamp);
       int upperWindowIndex = Collections.binarySearch(boundaries,
         file.getMaximumTimestamp() == null ? (Long)Long.MAX_VALUE : file.getMaximumTimestamp());
       // Handle boundary conditions and negative values of binarySearch
       lowerWindowIndex = (lowerWindowIndex < 0) ? Math.abs(lowerWindowIndex + 2) : lowerWindowIndex;
       upperWindowIndex = (upperWindowIndex < 0) ? Math.abs(upperWindowIndex + 2) : upperWindowIndex;
       if (lowerWindowIndex != upperWindowIndex) {
         LOG.debug("Major compaction triggered on store " + this + "; because file "
           + file.getPath() + " has data with timestamps cross window boundaries");
         return true;
       } else if (filesInWindow[upperWindowIndex]) {
         LOG.debug("Major compaction triggered on store " + this +
           "; because there are more than one file in some windows");
         return true;
       } else {
         filesInWindow[upperWindowIndex] = true;
       }
       hdfsBlocksDistribution.add(file.getHDFSBlockDistribution());
     }
 
     float blockLocalityIndex = hdfsBlocksDistribution
         .getBlockLocalityIndex(RSRpcServices.getHostname(comConf.conf, false));
     if (blockLocalityIndex < comConf.getMinLocalityToForceCompact()) {
       LOG.debug("Major compaction triggered on store " + this
         + "; to make hdfs blocks local, current blockLocalityIndex is "
         + blockLocalityIndex + " (min " + comConf.getMinLocalityToForceCompact() + ")");
       return true;
     }
 
     LOG.debug("Skipping major compaction of " + this +
       ", because the files are already major compacted");
     return false;
   }
 
   @Override
   protected CompactionRequest createCompactionRequest(ArrayList<StoreFile> candidateSelection,
     boolean tryingMajor, boolean mayUseOffPeak, boolean mayBeStuck) throws IOException {
     CompactionRequest result = tryingMajor ? selectMajorCompaction(candidateSelection)
       : selectMinorCompaction(candidateSelection, mayUseOffPeak, mayBeStuck);
     if (LOG.isDebugEnabled()) {
       LOG.debug("Generated compaction request: " + result);
     }
     return result;
   }
 
   public CompactionRequest selectMajorCompaction(ArrayList<StoreFile> candidateSelection) {
     long now = EnvironmentEdgeManager.currentTime();
     return new DateTieredCompactionRequest(candidateSelection,
       this.getCompactBoundariesForMajor(candidateSelection, now));
   }
 
   /**
    * We receive store files sorted in ascending order by seqId then scan the list of files. If the
    * current file has a maxTimestamp older than last known maximum, treat this file as it carries
    * the last known maximum. This way both seqId and timestamp are in the same order. If files carry
    * the same maxTimestamps, they are ordered by seqId. We then reverse the list so they are ordered
    * by seqId and maxTimestamp in descending order and build the time windows. All the out-of-order
    * data into the same compaction windows, guaranteeing contiguous compaction based on sequence id.
    */
   public CompactionRequest selectMinorCompaction(ArrayList<StoreFile> candidateSelection,
       boolean mayUseOffPeak, boolean mayBeStuck) throws IOException {
     long now = EnvironmentEdgeManager.currentTime();
     long oldestToCompact = getOldestToCompact(comConf.getDateTieredMaxStoreFileAgeMillis(), now);
 
     List<Pair<StoreFile, Long>> storefileMaxTimestampPairs =
         Lists.newArrayListWithCapacity(candidateSelection.size());
     long maxTimestampSeen = Long.MIN_VALUE;
     for (StoreFile storeFile : candidateSelection) {
       // if there is out-of-order data,
       // we put them in the same window as the last file in increasing order
       maxTimestampSeen = Math.max(maxTimestampSeen,
         storeFile.getMaximumTimestamp() == null? Long.MIN_VALUE : storeFile.getMaximumTimestamp());
       storefileMaxTimestampPairs.add(new Pair<StoreFile, Long>(storeFile, maxTimestampSeen));
     }
     Collections.reverse(storefileMaxTimestampPairs);
 
     CompactionWindow window = getIncomingWindow(now);
     int minThreshold = comConf.getDateTieredIncomingWindowMin();
     PeekingIterator<Pair<StoreFile, Long>> it =
         Iterators.peekingIterator(storefileMaxTimestampPairs.iterator());
     while (it.hasNext()) {
       if (window.compareToTimestamp(oldestToCompact) < 0) {
         break;
       }
       int compResult = window.compareToTimestamp(it.peek().getSecond());
       if (compResult > 0) {
         // If the file is too old for the window, switch to the next window
         window = window.nextEarlierWindow();
         minThreshold = comConf.getMinFilesToCompact();
       } else {
         // The file is within the target window
         ArrayList<StoreFile> fileList = Lists.newArrayList();
         // Add all files in the same window. For incoming window
         // we tolerate files with future data although it is sub-optimal
         while (it.hasNext() && window.compareToTimestamp(it.peek().getSecond()) <= 0) {
           fileList.add(it.next().getFirst());
         }
         if (fileList.size() >= minThreshold) {
           if (LOG.isDebugEnabled()) {
             LOG.debug("Processing files: " + fileList + " for window: " + window);
           }
           DateTieredCompactionRequest request = generateCompactionRequest(fileList, window,
             mayUseOffPeak, mayBeStuck, minThreshold);
           if (request != null) {
             return request;
           }
         }
       }
     }
     // A non-null file list is expected by HStore
     return new CompactionRequest(Collections.<StoreFile> emptyList());
   }
 
   private DateTieredCompactionRequest generateCompactionRequest(ArrayList<StoreFile> storeFiles,
       CompactionWindow window, boolean mayUseOffPeak, boolean mayBeStuck, int minThreshold)
       throws IOException {
     // The files has to be in ascending order for ratio-based compaction to work right
     // and removeExcessFile to exclude youngest files.
     Collections.reverse(storeFiles);
 
     // Compact everything in the window if have more files than comConf.maxBlockingFiles
     compactionPolicyPerWindow.setMinThreshold(minThreshold);
     ArrayList<StoreFile> storeFileSelection = mayBeStuck ? storeFiles
       : compactionPolicyPerWindow.applyCompactionPolicy(storeFiles, mayUseOffPeak, false);
     if (storeFileSelection != null && !storeFileSelection.isEmpty()) {
       // If there is any file in the window excluded from compaction,
       // only one file will be output from compaction.
       boolean singleOutput = storeFiles.size() != storeFileSelection.size() ||
         comConf.useDateTieredSingleOutputForMinorCompaction();
       List<Long> boundaries = getCompactionBoundariesForMinor(window, singleOutput);
       DateTieredCompactionRequest result = new DateTieredCompactionRequest(storeFileSelection,
         boundaries);
       return result;
     }
     return null;
   }
 
   /**
    * Return a list of boundaries for multiple compaction output
    *   in ascending order.
    */
   private List<Long> getCompactBoundariesForMajor(Collection<StoreFile> filesToCompact, long now) {
     long minTimestamp = Long.MAX_VALUE;
     for (StoreFile file : filesToCompact) {
       minTimestamp =
         Math.min(minTimestamp,
           file.getMinimumTimestamp() == null ? Long.MAX_VALUE : file.getMinimumTimestamp());
     }
 
     List<Long> boundaries = new ArrayList<Long>();
 
     // Add startMillis of all windows between now and min timestamp
     for (CompactionWindow window = getIncomingWindow(now);
         window.compareToTimestamp(minTimestamp) > 0;
         window = window.nextEarlierWindow()) {
       boundaries.add(window.startMillis());
     }
     boundaries.add(Long.MIN_VALUE);
     Collections.reverse(boundaries);
     return boundaries;
   }
 
   /**
    * @return a list of boundaries for multiple compaction output from minTimestamp to maxTimestamp.
    */
   private static List<Long> getCompactionBoundariesForMinor(CompactionWindow window,
       boolean singleOutput) {
     List<Long> boundaries = new ArrayList<Long>();
     boundaries.add(Long.MIN_VALUE);
     if (!singleOutput) {
       boundaries.add(window.startMillis());
     }
     return boundaries;
   }
 
   private CompactionWindow getIncomingWindow(long now) {
     return windowFactory.newIncomingWindow(now);
   }
 
   private static long getOldestToCompact(long maxAgeMillis, long now) {
     try {
       return LongMath.checkedSubtract(now, maxAgeMillis);
     } catch (ArithmeticException ae) {
       LOG.warn("Value for " + CompactionConfiguration.DATE_TIERED_MAX_AGE_MILLIS_KEY + ": "
           + maxAgeMillis + ". All the files will be eligible for minor compaction.");
       return Long.MIN_VALUE;
     }
   }
 }