/**
    *
    * 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 static org.junit.Assert.assertEquals;
  import static org.junit.Assert.assertNotNull;
  import static org.junit.Assert.assertNull;
  import static org.junit.Assert.assertTrue;
  
  import java.nio.ByteBuffer;
  import java.util.Random;
  
  import org.apache.hadoop.hbase.testclassification.SmallTests;
  import org.apache.hadoop.hbase.io.HeapSize;
  import org.apache.hadoop.hbase.io.hfile.LruBlockCache.EvictionThread;
  import org.apache.hadoop.hbase.util.ClassSize;
  import org.junit.Test;
  import org.junit.experimental.categories.Category;
  
  /**
   * Tests the concurrent LruBlockCache.<p>
   *
   * Tests will ensure it grows and shrinks in size properly,
   * evictions run when they're supposed to and do what they should,
   * and that cached blocks are accessible when expected to be.
   */
  @Category(SmallTests.class)
  public class TestLruBlockCache {
  
  
    @Test
    public void testBackgroundEvictionThread() throws Exception {
      long maxSize = 100000;
      int numBlocks = 9;
      long blockSize = calculateBlockSizeDefault(maxSize, numBlocks);
      assertTrue("calculateBlockSize appears broken.", blockSize * numBlocks <= maxSize);
  
      LruBlockCache cache = new LruBlockCache(maxSize,blockSize);
      EvictionThread evictionThread = cache.getEvictionThread();
      assertTrue(evictionThread != null);
  
      CachedItem[] blocks = generateFixedBlocks(numBlocks + 1, blockSize, "block");
  
      // Make sure eviction thread has entered run method
      while (!evictionThread.isEnteringRun()) {
        Thread.sleep(1);
      }
  
      // Add all the blocks
      for (CachedItem block : blocks) {
        cache.cacheBlock(block.cacheKey, block);
      }
  
      // wait until at least one eviction has run
      int n = 0;
      while(cache.getStats().getEvictionCount() == 0) {
        Thread.sleep(200);
        assertTrue("Eviction never happened.", n++ < 20);
      }
  
      // let cache stabilize
      // On some systems, the cache will run multiple evictions before it attains
      // steady-state. For instance, after populating the cache with 10 blocks,
      // the first eviction evicts a single block and then a second eviction
      // evicts another. I think this is due to the delta between minSize and
      // acceptableSize, combined with variance between object overhead on
      // different environments.
      n = 0;
      for (long prevCnt = 0 /* < number of blocks added */,
                curCnt = cache.getBlockCount();
          prevCnt != curCnt; prevCnt = curCnt, curCnt = cache.getBlockCount()) {
        Thread.sleep(200);
        assertTrue("Cache never stabilized.", n++ < 20);
      }
  
      long evictionCount = cache.getStats().getEvictionCount();
      assertTrue(evictionCount >= 1);
      System.out.println("Background Evictions run: " + evictionCount);
    }
  
    @Test
    public void testCacheSimple() throws Exception {
  
     long maxSize = 1000000;
     long blockSize = calculateBlockSizeDefault(maxSize, 101);
 
     LruBlockCache cache = new LruBlockCache(maxSize, blockSize);
 
     CachedItem [] blocks = generateRandomBlocks(100, blockSize);
 
     long expectedCacheSize = cache.heapSize();
 
     // Confirm empty
     for (CachedItem block : blocks) {
       assertTrue(cache.getBlock(block.cacheKey, true, false, true) == null);
     }
 
     // Add blocks
     for (CachedItem block : blocks) {
       cache.cacheBlock(block.cacheKey, block);
       expectedCacheSize += block.cacheBlockHeapSize();
     }
 
     // Verify correctly calculated cache heap size
     assertEquals(expectedCacheSize, cache.heapSize());
 
     // Check if all blocks are properly cached and retrieved
     for (CachedItem block : blocks) {
       HeapSize buf = cache.getBlock(block.cacheKey, true, false, true);
       assertTrue(buf != null);
       assertEquals(buf.heapSize(), block.heapSize());
     }
 
     // Re-add same blocks and ensure nothing has changed
     long expectedBlockCount = cache.getBlockCount();
     for (CachedItem block : blocks) {
       cache.cacheBlock(block.cacheKey, block);
     }
     assertEquals(
             "Cache should ignore cache requests for blocks already in cache",
             expectedBlockCount, cache.getBlockCount());
     
     // Verify correctly calculated cache heap size
     assertEquals(expectedCacheSize, cache.heapSize());
 
     // Check if all blocks are properly cached and retrieved
     for (CachedItem block : blocks) {
       HeapSize buf = cache.getBlock(block.cacheKey, true, false, true);
       assertTrue(buf != null);
       assertEquals(buf.heapSize(), block.heapSize());
     }
 
     // Expect no evictions
     assertEquals(0, cache.getStats().getEvictionCount());
     Thread t = new LruBlockCache.StatisticsThread(cache);
     t.start();
     t.join();
   }
 
   @Test
   public void testCacheEvictionSimple() throws Exception {
 
     long maxSize = 100000;
     long blockSize = calculateBlockSizeDefault(maxSize, 10);
 
     LruBlockCache cache = new LruBlockCache(maxSize,blockSize,false);
 
     CachedItem [] blocks = generateFixedBlocks(10, blockSize, "block");
 
     long expectedCacheSize = cache.heapSize();
 
     // Add all the blocks
     for (CachedItem block : blocks) {
       cache.cacheBlock(block.cacheKey, block);
       expectedCacheSize += block.cacheBlockHeapSize();
     }
 
     // A single eviction run should have occurred
     assertEquals(1, cache.getStats().getEvictionCount());
 
     // Our expected size overruns acceptable limit
     assertTrue(expectedCacheSize >
       (maxSize * LruBlockCache.DEFAULT_ACCEPTABLE_FACTOR));
 
     // But the cache did not grow beyond max
     assertTrue(cache.heapSize() < maxSize);
 
     // And is still below the acceptable limit
     assertTrue(cache.heapSize() <
         (maxSize * LruBlockCache.DEFAULT_ACCEPTABLE_FACTOR));
 
     // All blocks except block 0  should be in the cache
     assertTrue(cache.getBlock(blocks[0].cacheKey, true, false, true) == null);
     for(int i=1;i<blocks.length;i++) {
       assertEquals(cache.getBlock(blocks[i].cacheKey, true, false, true),
           blocks[i]);
     }
   }
 
   @Test
   public void testCacheEvictionTwoPriorities() throws Exception {
 
     long maxSize = 100000;
     long blockSize = calculateBlockSizeDefault(maxSize, 10);
 
     LruBlockCache cache = new LruBlockCache(maxSize,blockSize,false);
 
     CachedItem [] singleBlocks = generateFixedBlocks(5, 10000, "single");
     CachedItem [] multiBlocks = generateFixedBlocks(5, 10000, "multi");
 
     long expectedCacheSize = cache.heapSize();
 
     // Add and get the multi blocks
     for (CachedItem block : multiBlocks) {
       cache.cacheBlock(block.cacheKey, block);
       expectedCacheSize += block.cacheBlockHeapSize();
       assertEquals(cache.getBlock(block.cacheKey, true, false, true), block);
     }
 
     // Add the single blocks (no get)
     for (CachedItem block : singleBlocks) {
       cache.cacheBlock(block.cacheKey, block);
       expectedCacheSize += block.heapSize();
     }
 
     // A single eviction run should have occurred
     assertEquals(cache.getStats().getEvictionCount(), 1);
 
     // We expect two entries evicted
     assertEquals(cache.getStats().getEvictedCount(), 2);
 
     // Our expected size overruns acceptable limit
     assertTrue(expectedCacheSize >
       (maxSize * LruBlockCache.DEFAULT_ACCEPTABLE_FACTOR));
 
     // But the cache did not grow beyond max
     assertTrue(cache.heapSize() <= maxSize);
 
     // And is now below the acceptable limit
     assertTrue(cache.heapSize() <=
         (maxSize * LruBlockCache.DEFAULT_ACCEPTABLE_FACTOR));
 
     // We expect fairness across the two priorities.
     // This test makes multi go barely over its limit, in-memory
     // empty, and the rest in single.  Two single evictions and
     // one multi eviction expected.
     assertTrue(cache.getBlock(singleBlocks[0].cacheKey, true, false, true) == null);
     assertTrue(cache.getBlock(multiBlocks[0].cacheKey, true, false, true) == null);
 
     // And all others to be cached
     for(int i=1;i<4;i++) {
       assertEquals(cache.getBlock(singleBlocks[i].cacheKey, true, false, true),
           singleBlocks[i]);
       assertEquals(cache.getBlock(multiBlocks[i].cacheKey, true, false, true),
           multiBlocks[i]);
     }
   }
 
   @Test
   public void testCacheEvictionThreePriorities() throws Exception {
 
     long maxSize = 100000;
     long blockSize = calculateBlockSize(maxSize, 10);
 
     LruBlockCache cache = new LruBlockCache(maxSize, blockSize, false,
         (int)Math.ceil(1.2*maxSize/blockSize),
         LruBlockCache.DEFAULT_LOAD_FACTOR,
         LruBlockCache.DEFAULT_CONCURRENCY_LEVEL,
         0.98f, // min
         0.99f, // acceptable
         0.33f, // single
         0.33f, // multi
         0.34f, // memory
         1.2f,  // limit
         false,
         16 * 1024 * 1024);
 
     CachedItem [] singleBlocks = generateFixedBlocks(5, blockSize, "single");
     CachedItem [] multiBlocks = generateFixedBlocks(5, blockSize, "multi");
     CachedItem [] memoryBlocks = generateFixedBlocks(5, blockSize, "memory");
 
     long expectedCacheSize = cache.heapSize();
 
     // Add 3 blocks from each priority
     for(int i=0;i<3;i++) {
 
       // Just add single blocks
       cache.cacheBlock(singleBlocks[i].cacheKey, singleBlocks[i]);
       expectedCacheSize += singleBlocks[i].cacheBlockHeapSize();
 
       // Add and get multi blocks
       cache.cacheBlock(multiBlocks[i].cacheKey, multiBlocks[i]);
       expectedCacheSize += multiBlocks[i].cacheBlockHeapSize();
       cache.getBlock(multiBlocks[i].cacheKey, true, false, true);
 
       // Add memory blocks as such
       cache.cacheBlock(memoryBlocks[i].cacheKey, memoryBlocks[i], true, false);
       expectedCacheSize += memoryBlocks[i].cacheBlockHeapSize();
 
     }
 
     // Do not expect any evictions yet
     assertEquals(0, cache.getStats().getEvictionCount());
 
     // Verify cache size
     assertEquals(expectedCacheSize, cache.heapSize());
 
     // Insert a single block, oldest single should be evicted
     cache.cacheBlock(singleBlocks[3].cacheKey, singleBlocks[3]);
 
     // Single eviction, one thing evicted
     assertEquals(1, cache.getStats().getEvictionCount());
     assertEquals(1, cache.getStats().getEvictedCount());
 
     // Verify oldest single block is the one evicted
     assertEquals(null, cache.getBlock(singleBlocks[0].cacheKey, true, false, true));
 
     // Change the oldest remaining single block to a multi
     cache.getBlock(singleBlocks[1].cacheKey, true, false, true);
 
     // Insert another single block
     cache.cacheBlock(singleBlocks[4].cacheKey, singleBlocks[4]);
 
     // Two evictions, two evicted.
     assertEquals(2, cache.getStats().getEvictionCount());
     assertEquals(2, cache.getStats().getEvictedCount());
 
     // Oldest multi block should be evicted now
     assertEquals(null, cache.getBlock(multiBlocks[0].cacheKey, true, false, true));
 
     // Insert another memory block
     cache.cacheBlock(memoryBlocks[3].cacheKey, memoryBlocks[3], true, false);
 
     // Three evictions, three evicted.
     assertEquals(3, cache.getStats().getEvictionCount());
     assertEquals(3, cache.getStats().getEvictedCount());
 
     // Oldest memory block should be evicted now
     assertEquals(null, cache.getBlock(memoryBlocks[0].cacheKey, true, false, true));
 
     // Add a block that is twice as big (should force two evictions)
     CachedItem [] bigBlocks = generateFixedBlocks(3, blockSize*3, "big");
     cache.cacheBlock(bigBlocks[0].cacheKey, bigBlocks[0]);
 
     // Four evictions, six evicted (inserted block 3X size, expect +3 evicted)
     assertEquals(4, cache.getStats().getEvictionCount());
     assertEquals(6, cache.getStats().getEvictedCount());
 
     // Expect three remaining singles to be evicted
     assertEquals(null, cache.getBlock(singleBlocks[2].cacheKey, true, false, true));
     assertEquals(null, cache.getBlock(singleBlocks[3].cacheKey, true, false, true));
     assertEquals(null, cache.getBlock(singleBlocks[4].cacheKey, true, false, true));
 
     // Make the big block a multi block
     cache.getBlock(bigBlocks[0].cacheKey, true, false, true);
 
     // Cache another single big block
     cache.cacheBlock(bigBlocks[1].cacheKey, bigBlocks[1]);
 
     // Five evictions, nine evicted (3 new)
     assertEquals(5, cache.getStats().getEvictionCount());
     assertEquals(9, cache.getStats().getEvictedCount());
 
     // Expect three remaining multis to be evicted
     assertEquals(null, cache.getBlock(singleBlocks[1].cacheKey, true, false, true));
     assertEquals(null, cache.getBlock(multiBlocks[1].cacheKey, true, false, true));
     assertEquals(null, cache.getBlock(multiBlocks[2].cacheKey, true, false, true));
 
     // Cache a big memory block
     cache.cacheBlock(bigBlocks[2].cacheKey, bigBlocks[2], true, false);
 
     // Six evictions, twelve evicted (3 new)
     assertEquals(6, cache.getStats().getEvictionCount());
     assertEquals(12, cache.getStats().getEvictedCount());
 
     // Expect three remaining in-memory to be evicted
     assertEquals(null, cache.getBlock(memoryBlocks[1].cacheKey, true, false, true));
     assertEquals(null, cache.getBlock(memoryBlocks[2].cacheKey, true, false, true));
     assertEquals(null, cache.getBlock(memoryBlocks[3].cacheKey, true, false, true));
   }
 
   @Test
   public void testCacheEvictionInMemoryForceMode() throws Exception {
     long maxSize = 100000;
     long blockSize = calculateBlockSize(maxSize, 10);
 
     LruBlockCache cache = new LruBlockCache(maxSize, blockSize, false,
         (int)Math.ceil(1.2*maxSize/blockSize),
         LruBlockCache.DEFAULT_LOAD_FACTOR,
         LruBlockCache.DEFAULT_CONCURRENCY_LEVEL,
         0.98f, // min
         0.99f, // acceptable
         0.2f, // single
         0.3f, // multi
         0.5f, // memory
         1.2f, // limit
         true,
         16 * 1024 * 1024);
 
     CachedItem [] singleBlocks = generateFixedBlocks(10, blockSize, "single");
     CachedItem [] multiBlocks = generateFixedBlocks(10, blockSize, "multi");
     CachedItem [] memoryBlocks = generateFixedBlocks(10, blockSize, "memory");
 
     long expectedCacheSize = cache.heapSize();
 
     // 0. Add 5 single blocks and 4 multi blocks to make cache full, si:mu:me = 5:4:0
     for(int i = 0; i < 4; i++) {
       // Just add single blocks
       cache.cacheBlock(singleBlocks[i].cacheKey, singleBlocks[i]);
       expectedCacheSize += singleBlocks[i].cacheBlockHeapSize();
       // Add and get multi blocks
       cache.cacheBlock(multiBlocks[i].cacheKey, multiBlocks[i]);
       expectedCacheSize += multiBlocks[i].cacheBlockHeapSize();
       cache.getBlock(multiBlocks[i].cacheKey, true, false, true);
     }
     // 5th single block
     cache.cacheBlock(singleBlocks[4].cacheKey, singleBlocks[4]);
     expectedCacheSize += singleBlocks[4].cacheBlockHeapSize();
     // Do not expect any evictions yet
     assertEquals(0, cache.getStats().getEvictionCount());
     // Verify cache size
     assertEquals(expectedCacheSize, cache.heapSize());
 
     // 1. Insert a memory block, oldest single should be evicted, si:mu:me = 4:4:1
     cache.cacheBlock(memoryBlocks[0].cacheKey, memoryBlocks[0], true, false);
     // Single eviction, one block evicted
     assertEquals(1, cache.getStats().getEvictionCount());
     assertEquals(1, cache.getStats().getEvictedCount());
     // Verify oldest single block (index = 0) is the one evicted
     assertEquals(null, cache.getBlock(singleBlocks[0].cacheKey, true, false, true));
 
     // 2. Insert another memory block, another single evicted, si:mu:me = 3:4:2
     cache.cacheBlock(memoryBlocks[1].cacheKey, memoryBlocks[1], true, false);
     // Two evictions, two evicted.
     assertEquals(2, cache.getStats().getEvictionCount());
     assertEquals(2, cache.getStats().getEvictedCount());
     // Current oldest single block (index = 1) should be evicted now
     assertEquals(null, cache.getBlock(singleBlocks[1].cacheKey, true, false, true));
 
     // 3. Insert 4 memory blocks, 2 single and 2 multi evicted, si:mu:me = 1:2:6
     cache.cacheBlock(memoryBlocks[2].cacheKey, memoryBlocks[2], true, false);
     cache.cacheBlock(memoryBlocks[3].cacheKey, memoryBlocks[3], true, false);
     cache.cacheBlock(memoryBlocks[4].cacheKey, memoryBlocks[4], true, false);
     cache.cacheBlock(memoryBlocks[5].cacheKey, memoryBlocks[5], true, false);
     // Three evictions, three evicted.
     assertEquals(6, cache.getStats().getEvictionCount());
     assertEquals(6, cache.getStats().getEvictedCount());
     // two oldest single blocks and two oldest multi blocks evicted
     assertEquals(null, cache.getBlock(singleBlocks[2].cacheKey, true, false, true));
     assertEquals(null, cache.getBlock(singleBlocks[3].cacheKey, true, false, true));
     assertEquals(null, cache.getBlock(multiBlocks[0].cacheKey, true, false, true));
     assertEquals(null, cache.getBlock(multiBlocks[1].cacheKey, true, false, true));
 
     // 4. Insert 3 memory blocks, the remaining 1 single and 2 multi evicted
     // si:mu:me = 0:0:9
     cache.cacheBlock(memoryBlocks[6].cacheKey, memoryBlocks[6], true, false);
     cache.cacheBlock(memoryBlocks[7].cacheKey, memoryBlocks[7], true, false);
     cache.cacheBlock(memoryBlocks[8].cacheKey, memoryBlocks[8], true, false);
     // Three evictions, three evicted.
     assertEquals(9, cache.getStats().getEvictionCount());
     assertEquals(9, cache.getStats().getEvictedCount());
     // one oldest single block and two oldest multi blocks evicted
     assertEquals(null, cache.getBlock(singleBlocks[4].cacheKey, true, false, true));
     assertEquals(null, cache.getBlock(multiBlocks[2].cacheKey, true, false, true));
     assertEquals(null, cache.getBlock(multiBlocks[3].cacheKey, true, false, true));
 
     // 5. Insert one memory block, the oldest memory evicted
     // si:mu:me = 0:0:9
     cache.cacheBlock(memoryBlocks[9].cacheKey, memoryBlocks[9], true, false);
     // one eviction, one evicted.
     assertEquals(10, cache.getStats().getEvictionCount());
     assertEquals(10, cache.getStats().getEvictedCount());
     // oldest memory block evicted
     assertEquals(null, cache.getBlock(memoryBlocks[0].cacheKey, true, false, true));
 
     // 6. Insert one new single block, itself evicted immediately since
     //    all blocks in cache are memory-type which have higher priority
     // si:mu:me = 0:0:9 (no change)
     cache.cacheBlock(singleBlocks[9].cacheKey, singleBlocks[9]);
     // one eviction, one evicted.
     assertEquals(11, cache.getStats().getEvictionCount());
     assertEquals(11, cache.getStats().getEvictedCount());
     // the single block just cached now evicted (can't evict memory)
     assertEquals(null, cache.getBlock(singleBlocks[9].cacheKey, true, false, true));
   }
 
   // test scan resistance
   @Test
   public void testScanResistance() throws Exception {
 
     long maxSize = 100000;
     long blockSize = calculateBlockSize(maxSize, 10);
 
     LruBlockCache cache = new LruBlockCache(maxSize, blockSize, false,
         (int)Math.ceil(1.2*maxSize/blockSize),
         LruBlockCache.DEFAULT_LOAD_FACTOR,
         LruBlockCache.DEFAULT_CONCURRENCY_LEVEL,
         0.66f, // min
         0.99f, // acceptable
         0.33f, // single
         0.33f, // multi
         0.34f, // memory
         1.2f,  // limit
         false,
         16 * 1024 * 1024);
 
     CachedItem [] singleBlocks = generateFixedBlocks(20, blockSize, "single");
     CachedItem [] multiBlocks = generateFixedBlocks(5, blockSize, "multi");
 
     // Add 5 multi blocks
     for (CachedItem block : multiBlocks) {
       cache.cacheBlock(block.cacheKey, block);
       cache.getBlock(block.cacheKey, true, false, true);
     }
 
     // Add 5 single blocks
     for(int i=0;i<5;i++) {
       cache.cacheBlock(singleBlocks[i].cacheKey, singleBlocks[i]);
     }
 
     // An eviction ran
     assertEquals(1, cache.getStats().getEvictionCount());
 
     // To drop down to 2/3 capacity, we'll need to evict 4 blocks
     assertEquals(4, cache.getStats().getEvictedCount());
 
     // Should have been taken off equally from single and multi
     assertEquals(null, cache.getBlock(singleBlocks[0].cacheKey, true, false, true));
     assertEquals(null, cache.getBlock(singleBlocks[1].cacheKey, true, false, true));
     assertEquals(null, cache.getBlock(multiBlocks[0].cacheKey, true, false, true));
     assertEquals(null, cache.getBlock(multiBlocks[1].cacheKey, true, false, true));
 
     // Let's keep "scanning" by adding single blocks.  From here on we only
     // expect evictions from the single bucket.
 
     // Every time we reach 10 total blocks (every 4 inserts) we get 4 single
     // blocks evicted.  Inserting 13 blocks should yield 3 more evictions and
     // 12 more evicted.
 
     for(int i=5;i<18;i++) {
       cache.cacheBlock(singleBlocks[i].cacheKey, singleBlocks[i]);
     }
 
     // 4 total evictions, 16 total evicted
     assertEquals(4, cache.getStats().getEvictionCount());
     assertEquals(16, cache.getStats().getEvictedCount());
 
     // Should now have 7 total blocks
     assertEquals(7, cache.getBlockCount());
 
   }
 
   @Test
   public void testMaxBlockSize() throws Exception {
     long maxSize = 100000;
     long blockSize = calculateBlockSize(maxSize, 10);
 
     LruBlockCache cache = new LruBlockCache(maxSize, blockSize, false,
         (int)Math.ceil(1.2*maxSize/blockSize),
         LruBlockCache.DEFAULT_LOAD_FACTOR,
         LruBlockCache.DEFAULT_CONCURRENCY_LEVEL,
         0.66f, // min
         0.99f, // acceptable
         0.33f, // single
         0.33f, // multi
         0.34f, // memory
         1.2f,  // limit
         false,
         1024);
     CachedItem [] tooLong = generateFixedBlocks(10, 1024+5, "long");
     CachedItem [] small = generateFixedBlocks(15, 600, "small");
 
 
     for (CachedItem i:tooLong) {
       cache.cacheBlock(i.cacheKey, i);
     }
     for (CachedItem i:small) {
       cache.cacheBlock(i.cacheKey, i);
     }
     assertEquals(15,cache.getBlockCount());
     for (CachedItem i:small) {
       assertNotNull(cache.getBlock(i.cacheKey, true, false, false));
     }
     for (CachedItem i:tooLong) {
       assertNull(cache.getBlock(i.cacheKey, true, false, false));
     }
 
     assertEquals(10, cache.getStats().getFailedInserts());
   }
 
   // test setMaxSize
   @Test
   public void testResizeBlockCache() throws Exception {
 
     long maxSize = 300000;
     long blockSize = calculateBlockSize(maxSize, 31);
 
     LruBlockCache cache = new LruBlockCache(maxSize, blockSize, false,
         (int)Math.ceil(1.2*maxSize/blockSize),
         LruBlockCache.DEFAULT_LOAD_FACTOR,
         LruBlockCache.DEFAULT_CONCURRENCY_LEVEL,
         0.98f, // min
         0.99f, // acceptable
         0.33f, // single
         0.33f, // multi
         0.34f, // memory
         1.2f,  // limit
         false,
         16 * 1024 * 1024);
 
     CachedItem [] singleBlocks = generateFixedBlocks(10, blockSize, "single");
     CachedItem [] multiBlocks = generateFixedBlocks(10, blockSize, "multi");
     CachedItem [] memoryBlocks = generateFixedBlocks(10, blockSize, "memory");
 
     // Add all blocks from all priorities
     for(int i=0;i<10;i++) {
 
       // Just add single blocks
       cache.cacheBlock(singleBlocks[i].cacheKey, singleBlocks[i]);
 
       // Add and get multi blocks
       cache.cacheBlock(multiBlocks[i].cacheKey, multiBlocks[i]);
       cache.getBlock(multiBlocks[i].cacheKey, true, false, true);
 
       // Add memory blocks as such
       cache.cacheBlock(memoryBlocks[i].cacheKey, memoryBlocks[i], true, false);
     }
 
     // Do not expect any evictions yet
     assertEquals(0, cache.getStats().getEvictionCount());
 
     // Resize to half capacity plus an extra block (otherwise we evict an extra)
     cache.setMaxSize((long)(maxSize * 0.5f));
 
     // Should have run a single eviction
     assertEquals(1, cache.getStats().getEvictionCount());
 
     // And we expect 1/2 of the blocks to be evicted
     assertEquals(15, cache.getStats().getEvictedCount());
 
     // And the oldest 5 blocks from each category should be gone
     for(int i=0;i<5;i++) {
       assertEquals(null, cache.getBlock(singleBlocks[i].cacheKey, true, false, true));
       assertEquals(null, cache.getBlock(multiBlocks[i].cacheKey, true, false, true));
       assertEquals(null, cache.getBlock(memoryBlocks[i].cacheKey, true, false, true));
     }
 
     // And the newest 5 blocks should still be accessible
     for(int i=5;i<10;i++) {
       assertEquals(singleBlocks[i], cache.getBlock(singleBlocks[i].cacheKey, true, false, true));
       assertEquals(multiBlocks[i], cache.getBlock(multiBlocks[i].cacheKey, true, false, true));
       assertEquals(memoryBlocks[i], cache.getBlock(memoryBlocks[i].cacheKey, true, false, true));
     }
   }
 
   // test metricsPastNPeriods
   @Test
   public void testPastNPeriodsMetrics() throws Exception {
    double delta = 0.01;
 
     // 3 total periods
     CacheStats stats = new CacheStats("test", 3);
 
     // No accesses, should be 0
     stats.rollMetricsPeriod();
     assertEquals(0.0, stats.getHitRatioPastNPeriods(), delta);
     assertEquals(0.0, stats.getHitCachingRatioPastNPeriods(), delta);
 
     // period 1, 1 hit caching, 1 hit non-caching, 2 miss non-caching
     // should be (2/4)=0.5 and (1/1)=1
     stats.hit(false, true, BlockType.DATA);
     stats.hit(true, true, BlockType.DATA);
     stats.miss(false, false, BlockType.DATA);
     stats.miss(false, false, BlockType.DATA);
     stats.rollMetricsPeriod();
     assertEquals(0.5, stats.getHitRatioPastNPeriods(), delta);
     assertEquals(1.0, stats.getHitCachingRatioPastNPeriods(), delta);
 
     // period 2, 1 miss caching, 3 miss non-caching
     // should be (2/8)=0.25 and (1/2)=0.5
     stats.miss(true, false, BlockType.DATA);
     stats.miss(false, false, BlockType.DATA);
     stats.miss(false, false, BlockType.DATA);
     stats.miss(false, false, BlockType.DATA);
     stats.rollMetricsPeriod();
     assertEquals(0.25, stats.getHitRatioPastNPeriods(), delta);
     assertEquals(0.5, stats.getHitCachingRatioPastNPeriods(), delta);
 
     // period 3, 2 hits of each type
     // should be (6/12)=0.5 and (3/4)=0.75
     stats.hit(false, true, BlockType.DATA);
     stats.hit(true, true, BlockType.DATA);
     stats.hit(false, true, BlockType.DATA);
     stats.hit(true, true, BlockType.DATA);
     stats.rollMetricsPeriod();
     assertEquals(0.5, stats.getHitRatioPastNPeriods(), delta);
     assertEquals(0.75, stats.getHitCachingRatioPastNPeriods(), delta);
 
     // period 4, evict period 1, two caching misses
     // should be (4/10)=0.4 and (2/5)=0.4
     stats.miss(true, false, BlockType.DATA);
     stats.miss(true, false, BlockType.DATA);
     stats.rollMetricsPeriod();
     assertEquals(0.4, stats.getHitRatioPastNPeriods(), delta);
     assertEquals(0.4, stats.getHitCachingRatioPastNPeriods(), delta);
 
     // period 5, evict period 2, 2 caching misses, 2 non-caching hit
     // should be (6/10)=0.6 and (2/6)=1/3
     stats.miss(true, false, BlockType.DATA);
     stats.miss(true, false, BlockType.DATA);
     stats.hit(false, true, BlockType.DATA);
     stats.hit(false, true, BlockType.DATA);
     stats.rollMetricsPeriod();
     assertEquals(0.6, stats.getHitRatioPastNPeriods(), delta);
     assertEquals((double)1/3, stats.getHitCachingRatioPastNPeriods(), delta);
 
     // period 6, evict period 3
     // should be (2/6)=1/3 and (0/4)=0
     stats.rollMetricsPeriod();
     assertEquals((double)1/3, stats.getHitRatioPastNPeriods(), delta);
     assertEquals(0.0, stats.getHitCachingRatioPastNPeriods(), delta);
 
     // period 7, evict period 4
     // should be (2/4)=0.5 and (0/2)=0
     stats.rollMetricsPeriod();
     assertEquals(0.5, stats.getHitRatioPastNPeriods(), delta);
     assertEquals(0.0, stats.getHitCachingRatioPastNPeriods(), delta);
 
     // period 8, evict period 5
     // should be 0 and 0
     stats.rollMetricsPeriod();
     assertEquals(0.0, stats.getHitRatioPastNPeriods(), delta);
     assertEquals(0.0, stats.getHitCachingRatioPastNPeriods(), delta);
 
     // period 9, one of each
     // should be (2/4)=0.5 and (1/2)=0.5
     stats.miss(true, false, BlockType.DATA);
     stats.miss(false, false, BlockType.DATA);
     stats.hit(true, true, BlockType.DATA);
     stats.hit(false, true, BlockType.DATA);
     stats.rollMetricsPeriod();
     assertEquals(0.5, stats.getHitRatioPastNPeriods(), delta);
     assertEquals(0.5, stats.getHitCachingRatioPastNPeriods(), delta);
   }
 
   private CachedItem [] generateFixedBlocks(int numBlocks, int size, String pfx) {
     CachedItem [] blocks = new CachedItem[numBlocks];
     for(int i=0;i<numBlocks;i++) {
       blocks[i] = new CachedItem(pfx + i, size);
     }
     return blocks;
   }
 
   private CachedItem [] generateFixedBlocks(int numBlocks, long size, String pfx) {
     return generateFixedBlocks(numBlocks, (int)size, pfx);
   }
 
   private CachedItem [] generateRandomBlocks(int numBlocks, long maxSize) {
     CachedItem [] blocks = new CachedItem[numBlocks];
     Random r = new Random();
     for(int i=0;i<numBlocks;i++) {
       blocks[i] = new CachedItem("block" + i, r.nextInt((int)maxSize)+1);
     }
     return blocks;
   }
 
   private long calculateBlockSize(long maxSize, int numBlocks) {
     long roughBlockSize = maxSize / numBlocks;
     int numEntries = (int)Math.ceil((1.2)*maxSize/roughBlockSize);
     long totalOverhead = LruBlockCache.CACHE_FIXED_OVERHEAD +
         ClassSize.CONCURRENT_HASHMAP +
         (numEntries * ClassSize.CONCURRENT_HASHMAP_ENTRY) +
         (LruBlockCache.DEFAULT_CONCURRENCY_LEVEL * ClassSize.CONCURRENT_HASHMAP_SEGMENT);
     long negateBlockSize = (long)(totalOverhead/numEntries);
     negateBlockSize += LruCachedBlock.PER_BLOCK_OVERHEAD;
     return ClassSize.align((long)Math.floor((roughBlockSize - negateBlockSize)*0.99f));
   }
 
   private long calculateBlockSizeDefault(long maxSize, int numBlocks) {
     long roughBlockSize = maxSize / numBlocks;
     int numEntries = (int)Math.ceil((1.2)*maxSize/roughBlockSize);
     long totalOverhead = LruBlockCache.CACHE_FIXED_OVERHEAD +
         ClassSize.CONCURRENT_HASHMAP +
         (numEntries * ClassSize.CONCURRENT_HASHMAP_ENTRY) +
         (LruBlockCache.DEFAULT_CONCURRENCY_LEVEL * ClassSize.CONCURRENT_HASHMAP_SEGMENT);
     long negateBlockSize = totalOverhead / numEntries;
     negateBlockSize += LruCachedBlock.PER_BLOCK_OVERHEAD;
     return ClassSize.align((long)Math.floor((roughBlockSize - negateBlockSize)*
         LruBlockCache.DEFAULT_ACCEPTABLE_FACTOR));
   }
 
   private static class CachedItem implements Cacheable {
     BlockCacheKey cacheKey;
     int size;
 
     CachedItem(String blockName, int size) {
       this.cacheKey = new BlockCacheKey(blockName, 0);
       this.size = size;
     }
 
     /** The size of this item reported to the block cache layer */
     @Override
     public long heapSize() {
       return ClassSize.align(size);
     }
 
     /** Size of the cache block holding this item. Used for verification. */
     public long cacheBlockHeapSize() {
       return LruCachedBlock.PER_BLOCK_OVERHEAD
           + ClassSize.align(cacheKey.heapSize())
           + ClassSize.align(size);
     }
 
     @Override
     public int getSerializedLength() {
       return 0;
     }
 
     @Override
     public CacheableDeserializer<Cacheable> getDeserializer() {
       return null;
     }
 
     @Override
     public void serialize(ByteBuffer destination) {
     }
     
     @Override
     public BlockType getBlockType() {
       return BlockType.DATA;
     }
 
   }
 
 }