com.thinkaurelius.titan.graphdb.util

Class ConcurrentLRUCache<V>

java.lang.Object

com.thinkaurelius.titan.graphdb.util.ConcurrentLRUCache<V>

public class ConcurrentLRUCache<V>
extends Object

A LRU cache implementation based upon ConcurrentHashMap and other techniques to reduce contention and synchronization overhead to utilize multiple CPU cores more effectively.

Note that the implementation does not follow a true LRU (least-recently-used) eviction strategy. Instead it strives to remove least recently used items but when the initial cleanup does not remove enough items to reach the 'acceptableWaterMark' limit, it can remove more items forcefully regardless of access order.

ADDED COMMENT: This class has been copied from the Apache Solr project (see license above). New method has been added "putIfAbsent" which has the same behaviour as normal CHM.putIfAbsent but cache maintenance operations are only done in context of a winner thread, in other words, whoever puts absent item to the map would run cache maintenance ops, everybody else would be just newly added item returned.

Since:

solr 1.4

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static interface	ConcurrentLRUCache.EvictionListener<V>
static class	ConcurrentLRUCache.Stats

Constructor Summary

Constructors

Constructor and Description
ConcurrentLRUCache(int size, int lowerWatermark)
ConcurrentLRUCache(int upperWaterMark, int lowerWaterMark, int acceptableWatermark, int initialSize, boolean runCleanupThread, boolean runNewThreadForCleanup, ConcurrentLRUCache.EvictionListener<V> evictionListener)

Method Summary

Modifier and Type	Method and Description
void	clear()
boolean	containsKey(Long key)
void	destroy()
protected void	finalize()
V	get(Long key)
Map<Long,V>	getLatestAccessedItems(int n)
Map<Long,com.thinkaurelius.titan.graphdb.util.ConcurrentLRUCache.CacheEntry<Long,V>>	getMap()
Map<Long,V>	getOldestAccessedItems(int n) Returns 'n' number of oldest accessed entries present in this cache.
ConcurrentLRUCache.Stats	getStats()
V	put(Long key, V val)
V	putIfAbsent(Long key, V val)
V	remove(Long key)
void	setAlive(boolean live)
int	size()

Methods inherited from class java.lang.Object

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

Constructor Detail

ConcurrentLRUCache

public ConcurrentLRUCache(int upperWaterMark,
                          int lowerWaterMark,
                          int acceptableWatermark,
                          int initialSize,
                          boolean runCleanupThread,
                          boolean runNewThreadForCleanup,
                          ConcurrentLRUCache.EvictionListener<V> evictionListener)

ConcurrentLRUCache

public ConcurrentLRUCache(int size,
                          int lowerWatermark)

Method Detail

setAlive

public void setAlive(boolean live)

get

public V get(Long key)

containsKey

public boolean containsKey(Long key)

remove

public V remove(Long key)

putIfAbsent

public V putIfAbsent(Long key,
                     V val)

put

public V put(Long key,
             V val)

getOldestAccessedItems

public Map<Long,V> getOldestAccessedItems(int n)

Returns 'n' number of oldest accessed entries present in this cache.

This uses a TreeSet to collect the 'n' oldest items ordered by ascending last access time and returns a LinkedHashMap containing 'n' or less than 'n' entries.

Parameters:

n - the number of oldest items needed

Returns:

a LinkedHashMap containing 'n' or less than 'n' entries

getLatestAccessedItems

public Map<Long,V> getLatestAccessedItems(int n)

size

public int size()

clear

public void clear()

getMap

public Map<Long,com.thinkaurelius.titan.graphdb.util.ConcurrentLRUCache.CacheEntry<Long,V>> getMap()

destroy

public void destroy()

getStats

public ConcurrentLRUCache.Stats getStats()

finalize

protected void finalize()
                 throws Throwable

Overrides:

finalize in class Object

Throws:

Throwable