/**
    * 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.io.hfile;
  
  import java.io.IOException;
  import java.nio.ByteBuffer;
  import java.util.NavigableMap;
  import java.util.NavigableSet;
  import java.util.concurrent.ConcurrentSkipListMap;
  import java.util.concurrent.ConcurrentSkipListSet;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.conf.Configuration;
  import org.apache.hadoop.hbase.metrics.impl.FastLongHistogram;
  import org.apache.hadoop.hbase.util.Bytes;
  import org.apache.hadoop.hbase.util.GsonUtil;
  
  
  import org.apache.hbase.thirdparty.com.google.gson.Gson;
  import org.apache.hbase.thirdparty.com.google.gson.TypeAdapter;
  import org.apache.hbase.thirdparty.com.google.gson.stream.JsonReader;
  import org.apache.hbase.thirdparty.com.google.gson.stream.JsonWriter;
  
  /**
   * Utilty for aggregating counts in CachedBlocks and toString/toJSON CachedBlocks and BlockCaches.
   * No attempt has been made at making this thread safe.
   */
  @InterfaceAudience.Private
  public class BlockCacheUtil {
  
    private static final Log LOG = LogFactory.getLog(BlockCacheUtil.class);
  
    public static final long NANOS_PER_SECOND = 1000000000;
  
    /**
     * Needed generating JSON.
     */
    private static final Gson GSON = GsonUtil.createGson()
      .registerTypeAdapter(FastLongHistogram.class, new TypeAdapter<FastLongHistogram>() {
  
        @Override
        public void write(JsonWriter out, FastLongHistogram value) throws IOException {
          AgeSnapshot snapshot = new AgeSnapshot(value);
          out.beginObject();
          out.name("mean").value(snapshot.getMean());
          out.name("min").value(snapshot.getMin());
          out.name("max").value(snapshot.getMax());
          out.name("75thPercentile").value(snapshot.get75thPercentile());
          out.name("95thPercentile").value(snapshot.get95thPercentile());
          out.name("98thPercentile").value(snapshot.get98thPercentile());
          out.name("99thPercentile").value(snapshot.get99thPercentile());
          out.name("999thPercentile").value(snapshot.get999thPercentile());
          out.endObject();
        }
  
        @Override
        public FastLongHistogram read(JsonReader in) throws IOException {
          throw new UnsupportedOperationException();
        }
      }).setPrettyPrinting().create();
  
    /**
     * @param cb
     * @return The block content as String.
     */
    public static String toString(final CachedBlock cb, final long now) {
      return "filename=" + cb.getFilename() + ", " + toStringMinusFileName(cb, now);
    }
  
    /**
     * Little data structure to hold counts for a file.
     * Used doing a toJSON.
     */
    static class CachedBlockCountsPerFile {
      private int count = 0;
      private long size = 0;
      private int countData = 0;
      private long sizeData = 0;
      private final String filename;
  
      CachedBlockCountsPerFile(final String filename) {
        this.filename = filename;
     }
 
     public int getCount() {
       return count;
     }
 
     public long getSize() {
       return size;
     }
 
     public int getCountData() {
       return countData;
     }
 
     public long getSizeData() {
       return sizeData;
     }
 
     public String getFilename() {
       return filename;
     }
   }
 
   /**
    * @return A JSON String of <code>filename</code> and counts of <code>blocks</code>
    */
   public static String toJSON(final String filename, final NavigableSet<CachedBlock> blocks)
       throws IOException {
     CachedBlockCountsPerFile counts = new CachedBlockCountsPerFile(filename);
     for (CachedBlock cb: blocks) {
       counts.count++;
       counts.size += cb.getSize();
       BlockType bt = cb.getBlockType();
       if (bt != null && bt.isData()) {
         counts.countData++;
         counts.sizeData += cb.getSize();
       }
     }
     return GSON.toJson(counts);
   }
 
   /**
    * @return JSON string of <code>cbsf</code> aggregated
    */
   public static String toJSON(final CachedBlocksByFile cbsbf) throws IOException {
     return GSON.toJson(cbsbf);
   }
 
   /**
    * @return JSON string of <code>bc</code> content.
    */
   public static String toJSON(final BlockCache bc) throws IOException {
     return GSON.toJson(bc);
   }
 
   /**
    * @param cb
    * @return The block content of <code>bc</code> as a String minus the filename.
    */
   public static String toStringMinusFileName(final CachedBlock cb, final long now) {
     return "offset=" + cb.getOffset() +
       ", size=" + cb.getSize() +
       ", age=" + (now - cb.getCachedTime()) +
       ", type=" + cb.getBlockType() +
       ", priority=" + cb.getBlockPriority();
   }
 
   /**
    * Get a {@link CachedBlocksByFile} instance and load it up by iterating content in
    * {@link BlockCache}.
    * @param conf Used to read configurations
    * @param bc Block Cache to iterate.
    * @return Laoded up instance of CachedBlocksByFile
    */
   public static CachedBlocksByFile getLoadedCachedBlocksByFile(final Configuration conf,
       final BlockCache bc) {
     CachedBlocksByFile cbsbf = new CachedBlocksByFile(conf);
     for (CachedBlock cb: bc) {
       if (cbsbf.update(cb)) break;
     }
     return cbsbf;
   }
 
   private static int compareCacheBlock(Cacheable left, Cacheable right,
                                        boolean includeNextBlockOnDiskSize) {
     ByteBuffer l = ByteBuffer.allocate(left.getSerializedLength());
     left.serialize(l, includeNextBlockOnDiskSize);
     ByteBuffer r = ByteBuffer.allocate(right.getSerializedLength());
     right.serialize(r, includeNextBlockOnDiskSize);
     return Bytes.compareTo(l.array(), l.arrayOffset(), l.limit(),
              r.array(), r.arrayOffset(), r.limit());
   }
 
   /**
    * Validate that the existing and newBlock are the same without including the nextBlockMetadata,
    * if not, throw an exception. If they are the same without the nextBlockMetadata, return the
    * comparison.
    * @param existing block that is existing in the cache.
    * @param newBlock block that is trying to be cached.
    * @param cacheKey the cache key of the blocks.
    * @return comparison of the existing block to the newBlock.
    */
   public static int validateBlockAddition(Cacheable existing, Cacheable newBlock,
       BlockCacheKey cacheKey) {
     int comparison = compareCacheBlock(existing, newBlock, false);
     if (comparison != 0) {
       throw new RuntimeException(
           "Cached block contents differ, which should not have happened." + "cacheKey:" + cacheKey);
     }
     if ((existing instanceof HFileBlock) && (newBlock instanceof HFileBlock)) {
       comparison = ((HFileBlock) existing).getNextBlockOnDiskSize()
           - ((HFileBlock) newBlock).getNextBlockOnDiskSize();
     }
     return comparison;
   }
 
   /**
    * Because of the region splitting, it's possible that the split key locate in the middle of a
    * block. So it's possible that both the daughter regions load the same block from their parent
    * HFile. When pread, we don't force the read to read all of the next block header. So when two
    * threads try to cache the same block, it's possible that one thread read all of the next block
    * header but the other one didn't. if the already cached block hasn't next block header but the
    * new block to cache has, then we can replace the existing block with the new block for better
    * performance.(HBASE-20447)
    * @param blockCache BlockCache to check
    * @param cacheKey the block cache key
    * @param newBlock the new block which try to put into the block cache.
    * @return true means need to replace existing block with new block for the same block cache key.
    *         false means just keep the existing block.
    */
   public static boolean shouldReplaceExistingCacheBlock(BlockCache blockCache,
       BlockCacheKey cacheKey, Cacheable newBlock) {
     Cacheable existingBlock = blockCache.getBlock(cacheKey, false, false, false);
     if (existingBlock == null) {
       return true;
     }
     int comparison = BlockCacheUtil.validateBlockAddition(existingBlock, newBlock, cacheKey);
     if (comparison < 0) {
       LOG.warn("Cached block contents differ by nextBlockOnDiskSize, the new block has "
           + "nextBlockOnDiskSize set. Caching new block.");
       return true;
     } else if (comparison > 0) {
       LOG.warn("Cached block contents differ by nextBlockOnDiskSize, the existing block has "
           + "nextBlockOnDiskSize set, Keeping cached block.");
       return false;
     } else {
       LOG.warn("Caching an already cached block: " + cacheKey
           + ". This is harmless and can happen in rare " + "cases (see HBASE-8547)");
       return false;
     }
   }
 
   /**
    * Use one of these to keep a running account of cached blocks by file.  Throw it away when done.
    * This is different than metrics in that it is stats on current state of a cache.
    * See getLoadedCachedBlocksByFile
    */
   public static class CachedBlocksByFile {
     private int count;
     private int dataBlockCount;
     private long size;
     private long dataSize;
     private final long now = System.nanoTime();
     /**
      * How many blocks to look at before we give up.
      * There could be many millions of blocks. We don't want the
      * ui to freeze while we run through 1B blocks... users will
      * think hbase dead. UI displays warning in red when stats
      * are incomplete.
      */
     private final int max;
     public static final int DEFAULT_MAX = 1000000;
 
     CachedBlocksByFile() {
       this(null);
     }
 
     CachedBlocksByFile(final Configuration c) {
       this.max = c == null? DEFAULT_MAX: c.getInt("hbase.ui.blockcache.by.file.max", DEFAULT_MAX);
     }
 
     /**
      * Map by filename. use concurent utils because we want our Map and contained blocks sorted.
      */
     private transient NavigableMap<String, NavigableSet<CachedBlock>> cachedBlockByFile =
       new ConcurrentSkipListMap<String, NavigableSet<CachedBlock>>();
     FastLongHistogram hist = new FastLongHistogram();
 
     /**
      * @param cb
      * @return True if full.... if we won't be adding any more.
      */
     public boolean update(final CachedBlock cb) {
       if (isFull()) return true;
       NavigableSet<CachedBlock> set = this.cachedBlockByFile.get(cb.getFilename());
       if (set == null) {
         set = new ConcurrentSkipListSet<CachedBlock>();
         this.cachedBlockByFile.put(cb.getFilename(), set);
       }
       set.add(cb);
       this.size += cb.getSize();
       this.count++;
       BlockType bt = cb.getBlockType();
       if (bt != null && bt.isData()) {
         this.dataBlockCount++;
         this.dataSize += cb.getSize();
       }
       long age = (this.now - cb.getCachedTime())/NANOS_PER_SECOND;
       this.hist.add(age, 1);
       return false;
     }
 
     /**
      * @return True if full; i.e. there are more items in the cache but we only loaded up
      * the maximum set in configuration <code>hbase.ui.blockcache.by.file.max</code>
      * (Default: DEFAULT_MAX).
      */
     public boolean isFull() {
       return this.count >= this.max;
     }
 
     public NavigableMap<String, NavigableSet<CachedBlock>> getCachedBlockStatsByFile() {
       return this.cachedBlockByFile;
     }
 
     /**
      * @return count of blocks in the cache
      */
     public int getCount() {
       return count;
     }
 
     public int getDataCount() {
       return dataBlockCount;
     }
 
     /**
      * @return size of blocks in the cache
      */
     public long getSize() {
       return size;
     }
 
     /**
      * @return Size of data.
      */
     public long getDataSize() {
       return dataSize;
     }
 
     public AgeSnapshot getAgeInCacheSnapshot() {
       return new AgeSnapshot(this.hist);
     }
 
     @Override
     public String toString() {
       AgeSnapshot snapshot = getAgeInCacheSnapshot();
       return "count=" + count + ", dataBlockCount=" + dataBlockCount + ", size=" + size +
           ", dataSize=" + getDataSize() +
           ", mean age=" + snapshot.getMean() +
           ", min age=" + snapshot.getMin() +
           ", max age=" + snapshot.getMax() +
           ", 75th percentile age="   + snapshot.get75thPercentile() +
           ", 95th percentile age="   + snapshot.get95thPercentile() +
           ", 98th percentile age="   + snapshot.get98thPercentile() +
           ", 99th percentile age="   + snapshot.get99thPercentile() +
           ", 99.9th percentile age=" + snapshot.get99thPercentile();
     }
   }
 }