Package org.apache.accumulo.core.file.blockfile.cache.tinylfu

Class TinyLfuBlockCache

java.lang.Object

org.apache.accumulo.core.file.blockfile.cache.tinylfu.TinyLfuBlockCache

All Implemented Interfaces:

BlockCache

public final class TinyLfuBlockCache
extends Object
implements BlockCache

A block cache that is memory bounded using the W-TinyLFU eviction algorithm. This implementation delegates to a Caffeine cache to provide concurrent O(1) read and write operations.

• W-TinyLFU: http://arxiv.org/pdf/1512.00727.pdf
• Caffeine: https://github.com/ben-manes/caffeine
• Cache design: http://highscalability.com/blog/2016/1/25/design-of-a-modern-cache.html

Nested Class Summary

Nested classes/interfaces inherited from interface org.apache.accumulo.core.spi.cache.BlockCache

BlockCache.Loader, BlockCache.Stats

Constructor Summary

Constructors

Constructor	Description
TinyLfuBlockCache(BlockCacheManager.Configuration conf, CacheType type)

Method Summary

Modifier and Type	Method	Description
CacheEntry	cacheBlock(String blockName, byte[] buffer)	Add block to cache.
CacheEntry	getBlock(String blockName)	Fetch block from cache.
CacheEntry	getBlock(String blockName, BlockCache.Loader loader)	This method allows a cache to prevent concurrent loads of the same block.
long	getMaxHeapSize()	Get the maximum amount of on heap memory this cache will use.
long	getMaxSize()	Get the maximum size of this cache.
BlockCache.Stats	getStats()	Get the statistics of this cache.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

TinyLfuBlockCache

public TinyLfuBlockCache(BlockCacheManager.Configuration conf,
                         CacheType type)

Method Detail

getMaxHeapSize

public long getMaxHeapSize()

Description copied from interface: BlockCache

Get the maximum amount of on heap memory this cache will use.

Specified by:

getMaxHeapSize in interface BlockCache

getMaxSize

public long getMaxSize()

Description copied from interface: BlockCache

Get the maximum size of this cache.

Specified by:

getMaxSize in interface BlockCache

Returns:

max size in bytes

getBlock

public CacheEntry getBlock(String blockName)

Description copied from interface: BlockCache

Fetch block from cache.

Specified by:

getBlock in interface BlockCache

Parameters:

blockName - Block name to fetch.

Returns:

Block or null if block is not in the cache.

cacheBlock

public CacheEntry cacheBlock(String blockName,
                             byte[] buffer)

Description copied from interface: BlockCache

Add block to cache.

Specified by:

cacheBlock in interface BlockCache

Parameters:

blockName - Zero-based file block number.

buffer - The block contents wrapped in a ByteBuffer.

getStats

public BlockCache.Stats getStats()

Description copied from interface: BlockCache

Get the statistics of this cache.

Specified by:

getStats in interface BlockCache

Returns:

statistics

getBlock

public CacheEntry getBlock(String blockName,
                           BlockCache.Loader loader)

Description copied from interface: BlockCache

This method allows a cache to prevent concurrent loads of the same block. However a cache implementation is not required to prevent concurrent loads. SynchronousLoadingBlockCache is an abstract class that a cache can extent which does prevent concurrent loading of the same block.

Specified by:

getBlock in interface BlockCache

Parameters:

blockName - Block name to fetch

loader - If the block is not present in the cache, the loader can be called to load it.

Returns:

Block or null if block is not in the cache or didn't load.