Package org.apache.accumulo.core.spi.cache

Interface BlockCache

All Known Implementing Classes:

LruBlockCache, SynchronousLoadingBlockCache, TinyLfuBlockCache

public interface BlockCache

Block cache interface.

Since:

2.0.0

Nested Class Summary

Nested Classes

Modifier and Type	Interface	Description
static interface	BlockCache.Loader
static interface	BlockCache.Stats	Cache statistics.

Method Summary

Modifier and Type	Method	Description
CacheEntry	cacheBlock(String blockName, byte[] buf)	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.

Method Detail

cacheBlock

CacheEntry cacheBlock(String blockName,
                      byte[] buf)

Add block to cache.

Parameters:

blockName - Zero-based file block number.

buf - The block contents wrapped in a ByteBuffer.

getBlock

CacheEntry getBlock(String blockName)

Fetch block from cache.

Parameters:

blockName - Block name to fetch.

Returns:

Block or null if block is not in the cache.

getBlock

CacheEntry getBlock(String blockName,
                    BlockCache.Loader loader)

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.

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.

getMaxHeapSize

long getMaxHeapSize()

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

getMaxSize

long getMaxSize()

Get the maximum size of this cache.

Returns:

max size in bytes

getStats

BlockCache.Stats getStats()

Get the statistics of this cache.

Returns:

statistics