LruAdaptiveBlockCache (Apache HBase 2.5.0 API)

java.lang.Object
- org.apache.hadoop.hbase.io.hfile.LruAdaptiveBlockCache

All Implemented Interfaces:

Iterable<CachedBlock>, HeapSize, BlockCache, FirstLevelBlockCache, ResizableBlockCache
```
@InterfaceAudience.Private
public class LruAdaptiveBlockCache
extends Object
implements FirstLevelBlockCache
```
This realisation improve performance of classical LRU cache up to 3 times via reduce GC job.
The classical block cache implementation that is memory-aware using HeapSize, memory-bound using an LRU eviction algorithm, and concurrent: backed by a ConcurrentHashMap and with a non-blocking eviction thread giving constant-time cacheBlock(org.apache.hadoop.hbase.io.hfile.BlockCacheKey, org.apache.hadoop.hbase.io.hfile.Cacheable, boolean) and getBlock(org.apache.hadoop.hbase.io.hfile.BlockCacheKey, boolean, boolean, boolean) operations.
Contains three levels of block priority to allow for scan-resistance and in-memory families ColumnFamilyDescriptorBuilder.setInMemory(boolean) (An in-memory column family is a column family that should be served from memory if possible): single-access, multiple-accesses, and in-memory priority. A block is added with an in-memory priority flag if ColumnFamilyDescriptor.isInMemory(), otherwise a block becomes a single access priority the first time it is read into this block cache. If a block is accessed again while in cache, it is marked as a multiple access priority block. This delineation of blocks is used to prevent scans from thrashing the cache adding a least-frequently-used element to the eviction algorithm.
Each priority is given its own chunk of the total cache to ensure fairness during eviction. Each priority will retain close to its maximum size, however, if any priority is not using its entire chunk the others are able to grow beyond their chunk size.
Instantiated at a minimum with the total size and average block size. All sizes are in bytes. The block size is not especially important as this cache is fully dynamic in its sizing of blocks. It is only used for pre-allocating data structures and in initial heap estimation of the map.
The detailed constructor defines the sizes for the three priorities (they should total to the maximum size defined). It also sets the levels that trigger and control the eviction thread.
The acceptable size is the cache size level which triggers the eviction process to start. It evicts enough blocks to get the size below the minimum size specified.
Eviction happens in a separate thread and involves a single full-scan of the map. It determines how many bytes must be freed to reach the minimum size, and then while scanning determines the fewest least-recently-used blocks necessary from each of the three priorities (would be 3 times bytes to free). It then uses the priority chunk sizes to evict fairly according to the relative sizes and usage.
Adaptive LRU cache lets speed up performance while we are reading much more data than can fit into BlockCache and it is the cause of a high rate of evictions. This in turn leads to heavy Garbage Collector works. So a lot of blocks put into BlockCache but never read, but spending a lot of CPU resources for cleaning. We could avoid this situation via parameters:
hbase.lru.cache.heavy.eviction.count.limit - set how many times we have to run the eviction process that starts to avoid putting data to BlockCache. By default it is 0 and it meats the feature will start at the beginning. But if we have some times short reading the same data and some times long-term reading - we can divide it by this parameter. For example we know that our short reading used to be about 1 minutes, then we have to set the parameter about 10 and it will enable the feature only for long time massive reading (after ~100 seconds). So when we use short-reading and want all of them in the cache we will have it (except for eviction of course). When we use long-term heavy reading the feature will be enabled after some time and bring better performance.
hbase.lru.cache.heavy.eviction.mb.size.limit - set how many bytes in 10 seconds desirable putting into BlockCache (and evicted from it). The feature will try to reach this value and maintain it. Don't try to set it too small because it leads to premature exit from this mode. For powerful CPUs (about 20-40 physical cores) it could be about 400-500 MB. Average system (~10 cores) 200-300 MB. Some weak systems (2-5 cores) may be good with 50-100 MB. How it works: we set the limit and after each ~10 second calculate how many bytes were freed. Overhead = Freed Bytes Sum (MB) * 100 / Limit (MB) - 100; For example we set the limit = 500 and were evicted 2000 MB. Overhead is: 2000 * 100 / 500 - 100 = 300% The feature is going to reduce a percent caching data blocks and fit evicted bytes closer to 100% (500 MB). Some kind of an auto-scaling. If freed bytes less then the limit we have got negative overhead. For example if were freed 200 MB: 200 * 100 / 500 - 100 = -60% The feature will increase the percent of caching blocks. That leads to fit evicted bytes closer to 100% (500 MB). The current situation we can find out in the log of RegionServer: BlockCache evicted (MB): 0, overhead (%): -100, heavy eviction counter: 0, current caching DataBlock (%): 100 - means no eviction, 100% blocks is caching BlockCache evicted (MB): 2000, overhead (%): 300, heavy eviction counter: 1, current caching DataBlock (%): 97 - means eviction begin, reduce of caching blocks by 3%. It help to tune your system and find out what value is better set. Don't try to reach 0% overhead, it is impossible. Quite good 50-100% overhead, it prevents premature exit from this mode.
hbase.lru.cache.heavy.eviction.overhead.coefficient - set how fast we want to get the result. If we know that our reading is heavy for a long time, we don't want to wait and can increase the coefficient and get good performance sooner. But if we aren't sure we can do it slowly and it could prevent premature exit from this mode. So, when the coefficient is higher we can get better performance when heavy reading is stable. But when reading is changing we can adjust to it and set the coefficient to lower value. For example, we set the coefficient = 0.01. It means the overhead (see above) will be multiplied by 0.01 and the result is the value of reducing percent caching blocks. For example, if the overhead = 300% and the coefficient = 0.01, then percent of caching blocks will reduce by 3%. Similar logic when overhead has got negative value (overshooting). Maybe it is just short-term fluctuation and we will try to stay in this mode. It helps avoid premature exit during short-term fluctuation. Backpressure has simple logic: more overshooting - more caching blocks.
Find more information about improvement: https://issues.apache.org/jira/browse/HBASE-23887

Nested Class Summary

Nested Classes
Modifier and Type	Class and Description
`private class`	`LruAdaptiveBlockCache.BlockBucket` Used to group blocks into priority buckets.
`(package private) static class`	`LruAdaptiveBlockCache.EvictionThread`
`(package private) static class`	`LruAdaptiveBlockCache.StatisticsThread`

Field Summary

Fields
Modifier and Type	Field and Description
`private float`	`acceptableFactor` Acceptable size of cache (no evictions if size < acceptable)
`private long`	`blockSize` Approximate block size
`static long`	`CACHE_FIXED_OVERHEAD`
`private int`	`cacheDataBlockPercent` Percent of cached data blocks
`private AtomicLong`	`count` Cache access count (sequential ID)
`private LongAdder`	`dataBlockElements` Current number of cached data block elements
`private LongAdder`	`dataBlockSize` Current size of data blocks
`(package private) static float`	`DEFAULT_ACCEPTABLE_FACTOR`
`(package private) static int`	`DEFAULT_CONCURRENCY_LEVEL`
`private static float`	`DEFAULT_HARD_CAPACITY_LIMIT_FACTOR`
`private static boolean`	`DEFAULT_IN_MEMORY_FORCE_MODE`
`(package private) static float`	`DEFAULT_LOAD_FACTOR`
`private static int`	`DEFAULT_LRU_CACHE_HEAVY_EVICTION_COUNT_LIMIT`
`private static long`	`DEFAULT_LRU_CACHE_HEAVY_EVICTION_MB_SIZE_LIMIT`
`private static float`	`DEFAULT_LRU_CACHE_HEAVY_EVICTION_OVERHEAD_COEFFICIENT`
`private static long`	`DEFAULT_MAX_BLOCK_SIZE`
`private static float`	`DEFAULT_MEMORY_FACTOR`
`private static float`	`DEFAULT_MIN_FACTOR`
`private static float`	`DEFAULT_MULTI_FACTOR`
`private static float`	`DEFAULT_SINGLE_FACTOR`
`private AtomicLong`	`elements` Current number of cached elements
`private boolean`	`evictionInProgress` Volatile boolean to track if we are in an eviction process or not
`private ReentrantLock`	`evictionLock` Eviction lock (locked when eviction in process)
`private LruAdaptiveBlockCache.EvictionThread`	`evictionThread` Eviction thread
`private boolean`	`forceInMemory` Whether in-memory hfile's data block has higher priority when evicting
`private float`	`hardCapacityLimitFactor` hard capacity limit
`private int`	`heavyEvictionCountLimit` Limit of count eviction process when start to avoid to cache blocks
`private long`	`heavyEvictionMbSizeLimit` Limit of volume eviction process when start to avoid to cache blocks
`private float`	`heavyEvictionOverheadCoefficient` Adjust auto-scaling via overhead of evition rate
`private static org.slf4j.Logger`	`LOG`
`private static String`	`LRU_ACCEPTABLE_FACTOR_CONFIG_NAME` Acceptable size of cache (no evictions if size < acceptable)
`private static String`	`LRU_CACHE_HEAVY_EVICTION_COUNT_LIMIT`
`private static String`	`LRU_CACHE_HEAVY_EVICTION_MB_SIZE_LIMIT`
`private static String`	`LRU_CACHE_HEAVY_EVICTION_OVERHEAD_COEFFICIENT`
`(package private) static String`	`LRU_HARD_CAPACITY_LIMIT_FACTOR_CONFIG_NAME` Hard capacity limit of cache, will reject any put if size > this * acceptable
`private static String`	`LRU_IN_MEMORY_FORCE_MODE_CONFIG_NAME` Configuration key to force data-block always (except in-memory are too much) cached in memory for in-memory hfile, unlike inMemory, which is a column-family configuration, inMemoryForceMode is a cluster-wide configuration
`private static String`	`LRU_MAX_BLOCK_SIZE`
`private static String`	`LRU_MEMORY_PERCENTAGE_CONFIG_NAME`
`private static String`	`LRU_MIN_FACTOR_CONFIG_NAME` Percentage of total size that eviction will evict until; e.g.
`private static String`	`LRU_MULTI_PERCENTAGE_CONFIG_NAME`
`private static String`	`LRU_SINGLE_PERCENTAGE_CONFIG_NAME`
`private ConcurrentHashMap<BlockCacheKey,LruCachedBlock>`	`map` Defined the cache map as `ConcurrentHashMap` here, because in `getBlock(org.apache.hadoop.hbase.io.hfile.BlockCacheKey, boolean, boolean, boolean)`, we need to guarantee the atomicity of map#computeIfPresent (key, func).
`private long`	`maxBlockSize`
`private long`	`maxSize` Maximum allowable size of cache (block put if size > max, evict)
`private float`	`memoryFactor` In-memory bucket size
`private float`	`minFactor` Minimum threshold of cache (when evicting, evict until size < min)
`private float`	`multiFactor` Multiple access bucket size
`private long`	`overhead` Overhead of the structure itself
`private ScheduledExecutorService`	`scheduleThreadPool` Statistics thread schedule pool (for heavy debugging, could remove)
`private float`	`singleFactor` Single access bucket size
`private AtomicLong`	`size` Current size of cache
`private static int`	`STAT_THREAD_PERIOD`
`private CacheStats`	`stats` Cache statistics
`private BlockCache`	`victimHandler` Where to send victims (blocks evicted/missing from the cache).

Constructor Summary

Constructors
Constructor and Description
`LruAdaptiveBlockCache(long maxSize, long blockSize)` Default constructor.
`LruAdaptiveBlockCache(long maxSize, long blockSize, boolean evictionThread)` Constructor used for testing.
`LruAdaptiveBlockCache(long maxSize, long blockSize, boolean evictionThread, org.apache.hadoop.conf.Configuration conf)`
`LruAdaptiveBlockCache(long maxSize, long blockSize, boolean evictionThread, int mapInitialSize, float mapLoadFactor, int mapConcurrencyLevel, float minFactor, float acceptableFactor, float singleFactor, float multiFactor, float memoryFactor, float hardLimitFactor, boolean forceInMemory, long maxBlockSize, int heavyEvictionCountLimit, long heavyEvictionMbSizeLimit, float heavyEvictionOverheadCoefficient)` Configurable constructor.
`LruAdaptiveBlockCache(long maxSize, long blockSize, org.apache.hadoop.conf.Configuration conf)`

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`(package private) long`	`acceptableSize()`
`private Cacheable`	`asReferencedHeapBlock(Cacheable buf)` The block cached in LruAdaptiveBlockCache will always be an heap block: on the one side, the heap access will be more faster then off-heap, the small index block or meta block cached in CombinedBlockCache will benefit a lot.
`private static void`	`assertCounterSanity(long mapSize, long counterVal)` Sanity-checking for parity between actual block cache content and metrics.
`void`	`cacheBlock(BlockCacheKey cacheKey, Cacheable buf)` Cache the block with the specified name and buffer.
`void`	`cacheBlock(BlockCacheKey cacheKey, Cacheable buf, boolean inMemory)` Cache the block with the specified name and buffer.
`private static long`	`calculateOverhead(long maxSize, long blockSize, int concurrency)`
`void`	`clearCache()` Clears the cache.
`boolean`	`containsBlock(BlockCacheKey cacheKey)` Whether the cache contains block with specified cacheKey
`(package private) long`	`evict()` Eviction method.
`boolean`	`evictBlock(BlockCacheKey cacheKey)` Evict block from cache.
`protected long`	`evictBlock(LruCachedBlock block, boolean evictedByEvictionProcess)` Evict the block, and it will be cached by the victim handler if exists && block may be read again later
`int`	`evictBlocksByHfileName(String hfileName)` Evicts all blocks for a specific HFile.
`Cacheable`	`getBlock(BlockCacheKey cacheKey, boolean caching, boolean repeat, boolean updateCacheMetrics)` Get the buffer of the block with the specified name.
`BlockCache[]`	`getBlockCaches()` Returns The list of sub blockcaches that make up this one; returns null if no sub caches.
`long`	`getBlockCount()` Returns the number of blocks currently cached in the block cache.
`int`	`getCacheDataBlockPercent()`
`long`	`getCurrentDataSize()` Returns the occupied size of data blocks, in bytes.
`long`	`getCurrentSize()` Returns the occupied size of the block cache, in bytes.
`long`	`getDataBlockCount()` Returns the number of data blocks currently cached in the block cache.
`Map<DataBlockEncoding,Integer>`	`getEncodingCountsForTest()`
`(package private) LruAdaptiveBlockCache.EvictionThread`	`getEvictionThread()`
`long`	`getFreeSize()` Returns the free size of the block cache, in bytes.
`(package private) Map<BlockCacheKey,LruCachedBlock>`	`getMapForTests()`
`long`	`getMaxSize()` Get the maximum size of this cache.
`(package private) long`	`getOverhead()`
`CacheStats`	`getStats()` Get counter statistics for this cache.
`long`	`heapSize()` Return the approximate 'exclusive deep size' of implementing object.
`(package private) boolean`	`isEvictionInProgress()`
`Iterator<CachedBlock>`	`iterator()` Returns Iterator over the blocks in the cache.
`void`	`logStats()`
`private long`	`memorySize()`
`private long`	`minSize()`
`private long`	`multiSize()`
`private void`	`runEviction()` Multi-threaded call to run the eviction process.
`void`	`setMaxSize(long maxSize)` Sets the max heap size that can be used by the BlockCache.
`void`	`setVictimCache(BlockCache victimCache)` Specifies the secondary cache.
`void`	`shutdown()` Shutdown the cache.
`private long`	`singleSize()`
`long`	`size()` Returns the total size of the block cache, in bytes.
`String`	`toString()`
`private long`	`updateSizeMetrics(LruCachedBlock cb, boolean evict)` Helper function that updates the local size counter and also updates any per-cf or per-blocktype metrics it can discern from given `LruCachedBlock`

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Methods inherited from interface org.apache.hadoop.hbase.io.hfile.BlockCache
isMetaBlock

Methods inherited from interface java.lang.Iterable
forEach, spliterator

- Field Detail
  - LOG
```
private static final org.slf4j.Logger LOG
```
  - LRU_MIN_FACTOR_CONFIG_NAME
```
private static final String LRU_MIN_FACTOR_CONFIG_NAME
```
    Percentage of total size that eviction will evict until; e.g. if set to .8, then we will keep evicting during an eviction run till the cache size is down to 80% of the total.
    
    See Also:
    
    Constant Field Values
  - LRU_ACCEPTABLE_FACTOR_CONFIG_NAME
```
private static final String LRU_ACCEPTABLE_FACTOR_CONFIG_NAME
```
    Acceptable size of cache (no evictions if size < acceptable)
    
    See Also:
    
    Constant Field Values
  - LRU_HARD_CAPACITY_LIMIT_FACTOR_CONFIG_NAME
```
static final String LRU_HARD_CAPACITY_LIMIT_FACTOR_CONFIG_NAME
```
    Hard capacity limit of cache, will reject any put if size > this * acceptable
    
    See Also:
    
    Constant Field Values
  - LRU_SINGLE_PERCENTAGE_CONFIG_NAME
```
private static final String LRU_SINGLE_PERCENTAGE_CONFIG_NAME
```
    See Also:
    
    Constant Field Values
  - LRU_MULTI_PERCENTAGE_CONFIG_NAME
```
private static final String LRU_MULTI_PERCENTAGE_CONFIG_NAME
```
    See Also:
    
    Constant Field Values
  - LRU_MEMORY_PERCENTAGE_CONFIG_NAME
```
private static final String LRU_MEMORY_PERCENTAGE_CONFIG_NAME
```
    See Also:
    
    Constant Field Values
  - LRU_IN_MEMORY_FORCE_MODE_CONFIG_NAME
```
private static final String LRU_IN_MEMORY_FORCE_MODE_CONFIG_NAME
```
    Configuration key to force data-block always (except in-memory are too much) cached in memory for in-memory hfile, unlike inMemory, which is a column-family configuration, inMemoryForceMode is a cluster-wide configuration
    
    See Also:
    
    Constant Field Values
  - DEFAULT_LOAD_FACTOR
```
static final float DEFAULT_LOAD_FACTOR
```
    See Also:
    
    Constant Field Values
  - DEFAULT_CONCURRENCY_LEVEL
```
static final int DEFAULT_CONCURRENCY_LEVEL
```
    See Also:
    
    Constant Field Values
  - DEFAULT_MIN_FACTOR
```
private static final float DEFAULT_MIN_FACTOR
```
    See Also:
    
    Constant Field Values
  - DEFAULT_ACCEPTABLE_FACTOR
```
static final float DEFAULT_ACCEPTABLE_FACTOR
```
    See Also:
    
    Constant Field Values
  - DEFAULT_SINGLE_FACTOR
```
private static final float DEFAULT_SINGLE_FACTOR
```
    See Also:
    
    Constant Field Values
  - DEFAULT_MULTI_FACTOR
```
private static final float DEFAULT_MULTI_FACTOR
```
    See Also:
    
    Constant Field Values
  - DEFAULT_MEMORY_FACTOR
```
private static final float DEFAULT_MEMORY_FACTOR
```
    See Also:
    
    Constant Field Values
  - DEFAULT_HARD_CAPACITY_LIMIT_FACTOR
```
private static final float DEFAULT_HARD_CAPACITY_LIMIT_FACTOR
```
    See Also:
    
    Constant Field Values
  - DEFAULT_IN_MEMORY_FORCE_MODE
```
private static final boolean DEFAULT_IN_MEMORY_FORCE_MODE
```
    See Also:
    
    Constant Field Values
  - STAT_THREAD_PERIOD
```
private static final int STAT_THREAD_PERIOD
```
    See Also:
    
    Constant Field Values
  - LRU_MAX_BLOCK_SIZE
```
private static final String LRU_MAX_BLOCK_SIZE
```
    See Also:
    
    Constant Field Values
  - DEFAULT_MAX_BLOCK_SIZE
```
private static final long DEFAULT_MAX_BLOCK_SIZE
```
    See Also:
    
    Constant Field Values
  - LRU_CACHE_HEAVY_EVICTION_COUNT_LIMIT
```
private static final String LRU_CACHE_HEAVY_EVICTION_COUNT_LIMIT
```
    See Also:
    
    Constant Field Values
  - DEFAULT_LRU_CACHE_HEAVY_EVICTION_COUNT_LIMIT
```
private static final int DEFAULT_LRU_CACHE_HEAVY_EVICTION_COUNT_LIMIT
```
    See Also:
    
    Constant Field Values
  - LRU_CACHE_HEAVY_EVICTION_MB_SIZE_LIMIT
```
private static final String LRU_CACHE_HEAVY_EVICTION_MB_SIZE_LIMIT
```
    See Also:
    
    Constant Field Values
  - DEFAULT_LRU_CACHE_HEAVY_EVICTION_MB_SIZE_LIMIT
```
private static final long DEFAULT_LRU_CACHE_HEAVY_EVICTION_MB_SIZE_LIMIT
```
    See Also:
    
    Constant Field Values
  - LRU_CACHE_HEAVY_EVICTION_OVERHEAD_COEFFICIENT
```
private static final String LRU_CACHE_HEAVY_EVICTION_OVERHEAD_COEFFICIENT
```
    See Also:
    
    Constant Field Values
  - DEFAULT_LRU_CACHE_HEAVY_EVICTION_OVERHEAD_COEFFICIENT
```
private static final float DEFAULT_LRU_CACHE_HEAVY_EVICTION_OVERHEAD_COEFFICIENT
```
    See Also:
    
    Constant Field Values
  - map
```
private final transient ConcurrentHashMap<BlockCacheKey,LruCachedBlock> map
```
    Defined the cache map as ConcurrentHashMap here, because in getBlock(org.apache.hadoop.hbase.io.hfile.BlockCacheKey, boolean, boolean, boolean), we need to guarantee the atomicity of map#computeIfPresent (key, func). Besides, the func method must execute exactly once only when the key is present and under the lock context, otherwise the reference count will be messed up. Notice that the ConcurrentSkipListMap can not guarantee that.
  - evictionLock
```
private final transient ReentrantLock evictionLock
```
    Eviction lock (locked when eviction in process)
  - maxBlockSize
```
private final long maxBlockSize
```
  - evictionInProgress
```
private volatile boolean evictionInProgress
```
    Volatile boolean to track if we are in an eviction process or not
  - evictionThread
```
private final transient LruAdaptiveBlockCache.EvictionThread evictionThread
```
    Eviction thread
  - scheduleThreadPool
```
private final transient ScheduledExecutorService scheduleThreadPool
```
    Statistics thread schedule pool (for heavy debugging, could remove)
  - size
```
private final AtomicLong size
```
    Current size of cache
  - dataBlockSize
```
private final LongAdder dataBlockSize
```
    Current size of data blocks
  - elements
```
private final AtomicLong elements
```
    Current number of cached elements
  - dataBlockElements
```
private final LongAdder dataBlockElements
```
    Current number of cached data block elements
  - count
```
private final AtomicLong count
```
    Cache access count (sequential ID)
  - hardCapacityLimitFactor
```
private final float hardCapacityLimitFactor
```
    hard capacity limit
  - stats
```
private final CacheStats stats
```
    Cache statistics
  - maxSize
```
private long maxSize
```
    Maximum allowable size of cache (block put if size > max, evict)
  - blockSize
```
private final long blockSize
```
    Approximate block size
  - acceptableFactor
```
private final float acceptableFactor
```
    Acceptable size of cache (no evictions if size < acceptable)
  - minFactor
```
private final float minFactor
```
    Minimum threshold of cache (when evicting, evict until size < min)
  - singleFactor
```
private final float singleFactor
```
    Single access bucket size
  - multiFactor
```
private final float multiFactor
```
    Multiple access bucket size
  - memoryFactor
```
private final float memoryFactor
```
    In-memory bucket size
  - overhead
```
private final long overhead
```
    Overhead of the structure itself
  - forceInMemory
```
private boolean forceInMemory
```
    Whether in-memory hfile's data block has higher priority when evicting
  - victimHandler
```
private transient BlockCache victimHandler
```
    Where to send victims (blocks evicted/missing from the cache). This is used only when we use an external cache as L2. Note: See org.apache.hadoop.hbase.io.hfile.MemcachedBlockCache
  - cacheDataBlockPercent
```
private volatile int cacheDataBlockPercent
```
    Percent of cached data blocks
  - heavyEvictionCountLimit
```
private final int heavyEvictionCountLimit
```
    Limit of count eviction process when start to avoid to cache blocks
  - heavyEvictionMbSizeLimit
```
private final long heavyEvictionMbSizeLimit
```
    Limit of volume eviction process when start to avoid to cache blocks
  - heavyEvictionOverheadCoefficient
```
private final float heavyEvictionOverheadCoefficient
```
    Adjust auto-scaling via overhead of evition rate
  - CACHE_FIXED_OVERHEAD
```
public static final long CACHE_FIXED_OVERHEAD
```
- Constructor Detail
  - LruAdaptiveBlockCache
```
public LruAdaptiveBlockCache(long maxSize,
                             long blockSize)
```
    Default constructor. Specify maximum size and expected average block size (approximation is fine).
    All other factors will be calculated based on defaults specified in this class.
    
    Parameters:
    
    maxSize - maximum size of cache, in bytes
    
    blockSize - approximate size of each block, in bytes
  - LruAdaptiveBlockCache
```
public LruAdaptiveBlockCache(long maxSize,
                             long blockSize,
                             boolean evictionThread)
```
    Constructor used for testing. Allows disabling of the eviction thread.
  - LruAdaptiveBlockCache
```
public LruAdaptiveBlockCache(long maxSize,
                             long blockSize,
                             boolean evictionThread,
                             org.apache.hadoop.conf.Configuration conf)
```
  - LruAdaptiveBlockCache
```
public LruAdaptiveBlockCache(long maxSize,
                             long blockSize,
                             org.apache.hadoop.conf.Configuration conf)
```
  - LruAdaptiveBlockCache
```
public LruAdaptiveBlockCache(long maxSize,
                             long blockSize,
                             boolean evictionThread,
                             int mapInitialSize,
                             float mapLoadFactor,
                             int mapConcurrencyLevel,
                             float minFactor,
                             float acceptableFactor,
                             float singleFactor,
                             float multiFactor,
                             float memoryFactor,
                             float hardLimitFactor,
                             boolean forceInMemory,
                             long maxBlockSize,
                             int heavyEvictionCountLimit,
                             long heavyEvictionMbSizeLimit,
                             float heavyEvictionOverheadCoefficient)
```
    Configurable constructor. Use this constructor if not using defaults.
    
    Parameters:
    
    maxSize - maximum size of this cache, in bytes
    
    blockSize - expected average size of blocks, in bytes
    
    evictionThread - whether to run evictions in a bg thread or not
    
    mapInitialSize - initial size of backing ConcurrentHashMap
    
    mapLoadFactor - initial load factor of backing ConcurrentHashMap
    
    mapConcurrencyLevel - initial concurrency factor for backing CHM
    
    minFactor - percentage of total size that eviction will evict until
    
    acceptableFactor - percentage of total size that triggers eviction
    
    singleFactor - percentage of total size for single-access blocks
    
    multiFactor - percentage of total size for multiple-access blocks
    
    memoryFactor - percentage of total size for in-memory blocks
    
    hardLimitFactor - hard capacity limit
    
    forceInMemory - in-memory hfile's data block has higher priority when evicting
    
    maxBlockSize - maximum block size for caching
    
    heavyEvictionCountLimit - when starts AdaptiveLRU algoritm work
    
    heavyEvictionMbSizeLimit - how many bytes desirable putting into BlockCache
    
    heavyEvictionOverheadCoefficient - how aggressive AdaptiveLRU will reduce GC
- Method Detail
  - setVictimCache
```
public void setVictimCache(BlockCache victimCache)
```
    Description copied from interface: FirstLevelBlockCache
    
    Specifies the secondary cache. An entry that is evicted from this cache due to a size constraint will be inserted into the victim cache.
    
    Specified by:
    
    setVictimCache in interface FirstLevelBlockCache
    
    Parameters:
    
    victimCache - the second level cache
  - setMaxSize
```
public void setMaxSize(long maxSize)
```
    Description copied from interface: ResizableBlockCache
    
    Sets the max heap size that can be used by the BlockCache.
    
    Specified by:
    
    setMaxSize in interface ResizableBlockCache
    
    Parameters:
    
    maxSize - The max heap size.
  - getCacheDataBlockPercent
```
public int getCacheDataBlockPercent()
```
  - asReferencedHeapBlock
```
private Cacheable asReferencedHeapBlock(Cacheable buf)
```
    The block cached in LruAdaptiveBlockCache will always be an heap block: on the one side, the heap access will be more faster then off-heap, the small index block or meta block cached in CombinedBlockCache will benefit a lot. on other side, the LruAdaptiveBlockCache size is always calculated based on the total heap size, if caching an off-heap block in LruAdaptiveBlockCache, the heap size will be messed up. Here we will clone the block into an heap block if it's an off-heap block, otherwise just use the original block. The key point is maintain the refCnt of the block (HBASE-22127):
    1. if cache the cloned heap block, its refCnt is an totally new one, it's easy to handle;
    2. if cache the original heap block, we're sure that it won't be tracked in ByteBuffAllocator's reservoir, if both RPC and LruAdaptiveBlockCache release the block, then it can be garbage collected by JVM, so need a retain here.
    
    Parameters:
    
    buf - the original block
    
    Returns:
    
    an block with an heap memory backend.
  - cacheBlock
```
public void cacheBlock(BlockCacheKey cacheKey,
                       Cacheable buf,
                       boolean inMemory)
```
    Cache the block with the specified name and buffer.
    It is assumed this will NOT be called on an already cached block. In rare cases (HBASE-8547) this can happen, for which we compare the buffer contents.
    
    Specified by:
    
    cacheBlock in interface BlockCache
    
    Parameters:
    
    cacheKey - block's cache key
    
    buf - block buffer
    
    inMemory - if block is in-memory
  - assertCounterSanity
```
private static void assertCounterSanity(long mapSize,
                                        long counterVal)
```
    Sanity-checking for parity between actual block cache content and metrics. Intended only for use with TRACE level logging and -ea JVM.
  - cacheBlock
```
public void cacheBlock(BlockCacheKey cacheKey,
                       Cacheable buf)
```
    Cache the block with the specified name and buffer.
    TODO after HBASE-22005, we may cache an block which allocated from off-heap, but our LRU cache sizing is based on heap size, so we should handle this in HBASE-22127. It will introduce an switch whether make the LRU on-heap or not, if so we may need copy the memory to on-heap, otherwise the caching size is based on off-heap.
    
    Specified by:
    
    cacheBlock in interface BlockCache
    
    Parameters:
    
    cacheKey - block's cache key
    
    buf - block buffer
  - updateSizeMetrics
```
private long updateSizeMetrics(LruCachedBlock cb,
                               boolean evict)
```
    Helper function that updates the local size counter and also updates any per-cf or per-blocktype metrics it can discern from given LruCachedBlock
  - getBlock
```
public Cacheable getBlock(BlockCacheKey cacheKey,
                          boolean caching,
                          boolean repeat,
                          boolean updateCacheMetrics)
```
    Get the buffer of the block with the specified name.
    
    Specified by:
    
    getBlock in interface BlockCache
    
    Parameters:
    
    cacheKey - block's cache key
    
    caching - true if the caller caches blocks on cache misses
    
    repeat - Whether this is a repeat lookup for the same block (used to avoid double counting cache misses when doing double-check locking)
    
    updateCacheMetrics - Whether to update cache metrics or not
    
    Returns:
    
    buffer of specified cache key, or null if not in cache
  - containsBlock
```
public boolean containsBlock(BlockCacheKey cacheKey)
```
    Whether the cache contains block with specified cacheKey
    
    Specified by:
    
    containsBlock in interface FirstLevelBlockCache
    
    Parameters:
    
    cacheKey - cache key for the block
    
    Returns:
    
    true if contains the block
  - evictBlock
```
public boolean evictBlock(BlockCacheKey cacheKey)
```
    Description copied from interface: BlockCache
    
    Evict block from cache.
    
    Specified by:
    
    evictBlock in interface BlockCache
    
    Parameters:
    
    cacheKey - Block to evict
    
    Returns:
    
    true if block existed and was evicted, false if not
  - evictBlocksByHfileName
```
public int evictBlocksByHfileName(String hfileName)
```
    Evicts all blocks for a specific HFile. This is an expensive operation implemented as a linear-time search through all blocks in the cache. Ideally this should be a search in a log-access-time map.
    This is used for evict-on-close to remove all blocks of a specific HFile.
    
    Specified by:
    
    evictBlocksByHfileName in interface BlockCache
    
    Returns:
    
    the number of blocks evicted
  - evictBlock
```
protected long evictBlock(LruCachedBlock block,
                          boolean evictedByEvictionProcess)
```
    Evict the block, and it will be cached by the victim handler if exists && block may be read again later
    
    Parameters:
    
    evictedByEvictionProcess - true if the given block is evicted by EvictionThread
    
    Returns:
    
    the heap size of evicted block
  - runEviction
```
private void runEviction()
```
    Multi-threaded call to run the eviction process.
  - isEvictionInProgress
```
boolean isEvictionInProgress()
```
  - getOverhead
```
long getOverhead()
```
  - evict
```
long evict()
```
    Eviction method. Evict items in order of use, allowing delete items which haven't been used for the longest amount of time.
    
    Returns:
    
    how many bytes were freed
  - toString
```
public String toString()
```
    Overrides:
    
    toString in class Object
  - getMaxSize
```
public long getMaxSize()
```
    Get the maximum size of this cache.
    
    Specified by:
    
    getMaxSize in interface BlockCache
    
    Returns:
    
    max size in bytes
  - getCurrentSize
```
public long getCurrentSize()
```
    Description copied from interface: BlockCache
    
    Returns the occupied size of the block cache, in bytes.
    
    Specified by:
    
    getCurrentSize in interface BlockCache
    
    Returns:
    
    occupied space in cache, in bytes
  - getCurrentDataSize
```
public long getCurrentDataSize()
```
    Description copied from interface: BlockCache
    
    Returns the occupied size of data blocks, in bytes.
    
    Specified by:
    
    getCurrentDataSize in interface BlockCache
    
    Returns:
    
    occupied space in cache, in bytes
  - getFreeSize
```
public long getFreeSize()
```
    Description copied from interface: BlockCache
    
    Returns the free size of the block cache, in bytes.
    
    Specified by:
    
    getFreeSize in interface BlockCache
    
    Returns:
    
    free space in cache, in bytes
  - size
```
public long size()
```
    Description copied from interface: BlockCache
    
    Returns the total size of the block cache, in bytes.
    
    Specified by:
    
    size in interface BlockCache
    
    Returns:
    
    size of cache, in bytes
  - getBlockCount
```
public long getBlockCount()
```
    Description copied from interface: BlockCache
    
    Returns the number of blocks currently cached in the block cache.
    
    Specified by:
    
    getBlockCount in interface BlockCache
    
    Returns:
    
    number of blocks in the cache
  - getDataBlockCount
```
public long getDataBlockCount()
```
    Description copied from interface: BlockCache
    
    Returns the number of data blocks currently cached in the block cache.
    
    Specified by:
    
    getDataBlockCount in interface BlockCache
    
    Returns:
    
    number of blocks in the cache
  - getEvictionThread
```
LruAdaptiveBlockCache.EvictionThread getEvictionThread()
```
  - logStats
```
public void logStats()
```
  - getStats
```
public CacheStats getStats()
```
    Get counter statistics for this cache.
    Includes: total accesses, hits, misses, evicted blocks, and runs of the eviction processes.
    
    Specified by:
    
    getStats in interface BlockCache
  - heapSize
```
public long heapSize()
```
    Description copied from interface: HeapSize
    
    Return the approximate 'exclusive deep size' of implementing object. Includes count of payload and hosting object sizings.
    
    Specified by:
    
    heapSize in interface HeapSize
  - calculateOverhead
```
private static long calculateOverhead(long maxSize,
                                      long blockSize,
                                      int concurrency)
```
  - iterator
```
public Iterator<CachedBlock> iterator()
```
    Description copied from interface: BlockCache
    
    Returns Iterator over the blocks in the cache.
    
    Specified by:
    
    iterator in interface Iterable<CachedBlock>
    
    Specified by:
    
    iterator in interface BlockCache
  - acceptableSize
```
long acceptableSize()
```
  - minSize
```
private long minSize()
```
  - singleSize
```
private long singleSize()
```
  - multiSize
```
private long multiSize()
```
  - memorySize
```
private long memorySize()
```
  - shutdown
```
public void shutdown()
```
    Description copied from interface: BlockCache
    
    Shutdown the cache.
    
    Specified by:
    
    shutdown in interface BlockCache
  - clearCache
```
public void clearCache()
```
    Clears the cache. Used in tests.
  - getEncodingCountsForTest
```
public Map<DataBlockEncoding,Integer> getEncodingCountsForTest()
```
  - getMapForTests
```
Map<BlockCacheKey,LruCachedBlock> getMapForTests()
```
  - getBlockCaches
```
public BlockCache[] getBlockCaches()
```
    Description copied from interface: BlockCache
    
    Returns The list of sub blockcaches that make up this one; returns null if no sub caches.
    
    Specified by:
    
    getBlockCaches in interface BlockCache

Class LruAdaptiveBlockCache

Nested Class Summary

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Methods inherited from interface org.apache.hadoop.hbase.io.hfile.BlockCache

Methods inherited from interface java.lang.Iterable

Field Detail

LOG

LRU_MIN_FACTOR_CONFIG_NAME

LRU_ACCEPTABLE_FACTOR_CONFIG_NAME

LRU_HARD_CAPACITY_LIMIT_FACTOR_CONFIG_NAME

LRU_SINGLE_PERCENTAGE_CONFIG_NAME

LRU_MULTI_PERCENTAGE_CONFIG_NAME

LRU_MEMORY_PERCENTAGE_CONFIG_NAME

LRU_IN_MEMORY_FORCE_MODE_CONFIG_NAME

DEFAULT_LOAD_FACTOR

DEFAULT_CONCURRENCY_LEVEL

DEFAULT_MIN_FACTOR

DEFAULT_ACCEPTABLE_FACTOR

DEFAULT_SINGLE_FACTOR

DEFAULT_MULTI_FACTOR

DEFAULT_MEMORY_FACTOR

DEFAULT_HARD_CAPACITY_LIMIT_FACTOR

DEFAULT_IN_MEMORY_FORCE_MODE

STAT_THREAD_PERIOD

LRU_MAX_BLOCK_SIZE

DEFAULT_MAX_BLOCK_SIZE

LRU_CACHE_HEAVY_EVICTION_COUNT_LIMIT

DEFAULT_LRU_CACHE_HEAVY_EVICTION_COUNT_LIMIT

LRU_CACHE_HEAVY_EVICTION_MB_SIZE_LIMIT

DEFAULT_LRU_CACHE_HEAVY_EVICTION_MB_SIZE_LIMIT

LRU_CACHE_HEAVY_EVICTION_OVERHEAD_COEFFICIENT

DEFAULT_LRU_CACHE_HEAVY_EVICTION_OVERHEAD_COEFFICIENT

map

evictionLock

maxBlockSize

evictionInProgress

evictionThread

scheduleThreadPool

size

dataBlockSize

elements

dataBlockElements

count

hardCapacityLimitFactor

stats

maxSize

blockSize

acceptableFactor

minFactor

singleFactor

multiFactor

memoryFactor

overhead

forceInMemory

victimHandler

cacheDataBlockPercent

heavyEvictionCountLimit

heavyEvictionMbSizeLimit

heavyEvictionOverheadCoefficient

CACHE_FIXED_OVERHEAD

Constructor Detail

LruAdaptiveBlockCache

LruAdaptiveBlockCache

LruAdaptiveBlockCache

LruAdaptiveBlockCache

LruAdaptiveBlockCache

Method Detail

setVictimCache

setMaxSize

getCacheDataBlockPercent

asReferencedHeapBlock

cacheBlock

assertCounterSanity

cacheBlock

updateSizeMetrics

getBlock

containsBlock