Package org.apache.solr.util

Class ConcurrentLFUCache<K,V>

java.lang.Object

org.apache.solr.util.ConcurrentLFUCache<K,V>

All Implemented Interfaces:

org.apache.lucene.util.Accountable, Cache<K,V>

public class ConcurrentLFUCache<K,V>
extends Object
implements Cache<K,V>, org.apache.lucene.util.Accountable

A LFU cache implementation based upon ConcurrentHashMap.

This is not a terribly efficient implementation. The tricks used in the LRU version were not directly usable, perhaps it might be possible to rewrite them with LFU in mind.

This API is experimental and subject to change

Since:

solr 1.6

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	ConcurrentLFUCache.CacheEntry<K,V>
static interface	ConcurrentLFUCache.EvictionListener<K,V>
static class	ConcurrentLFUCache.Stats

Constructor Summary

Constructors

Constructor	Description
ConcurrentLFUCache(int size, int lowerWatermark)
ConcurrentLFUCache(int upperWaterMark, int lowerWaterMark, int acceptableSize, int initialSize, boolean runCleanupThread, boolean runNewThreadForCleanup, ConcurrentLFUCache.EvictionListener<K,V> evictionListener, boolean timeDecay)
ConcurrentLFUCache(int upperWaterMark, int lowerWaterMark, int acceptableSize, int initialSize, boolean runCleanupThread, boolean runNewThreadForCleanup, ConcurrentLFUCache.EvictionListener<K,V> evictionListener, boolean timeDecay, int maxIdleTimeSec)

Method Summary

Modifier and Type	Method	Description
void	clear()
V	computeIfAbsent(K key, Function<? super K,? extends V> mappingFunction)
void	destroy()
protected void	finalize()
V	get(K key)
Map<K,V>	getLeastUsedItems(int n)	Returns 'n' number of least used entries present in this cache.
Map<Object,ConcurrentLFUCache.CacheEntry<K,V>>	getMap()
Map<K,V>	getMostUsedItems(int n)	Returns 'n' number of most used entries present in this cache.
ConcurrentLFUCache.Stats	getStats()
void	markAndSweep()	Removes items from the cache to bring the size down to the lowerWaterMark.
V	put(K key, V val)
V	putCacheEntry(ConcurrentLFUCache.CacheEntry<K,V> e)	Visible for testing to create synthetic cache entries.
long	ramBytesUsed()
V	remove(K key)
void	setAcceptableWaterMark(int acceptableWaterMark)
void	setAlive(boolean live)
void	setLowerWaterMark(int lowerWaterMark)
void	setMaxIdleTime(int maxIdleTime)
void	setNewThreadForCleanup(boolean newThreadForCleanup)
void	setRunCleanupThread(boolean runCleanupThread)
void	setTimeDecay(boolean timeDecay)
void	setUpperWaterMark(int upperWaterMark)
int	size()

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.apache.lucene.util.Accountable

getChildResources

Constructor Detail

ConcurrentLFUCache

public ConcurrentLFUCache(int upperWaterMark,
                          int lowerWaterMark,
                          int acceptableSize,
                          int initialSize,
                          boolean runCleanupThread,
                          boolean runNewThreadForCleanup,
                          ConcurrentLFUCache.EvictionListener<K,V> evictionListener,
                          boolean timeDecay)

ConcurrentLFUCache

public ConcurrentLFUCache(int upperWaterMark,
                          int lowerWaterMark,
                          int acceptableSize,
                          int initialSize,
                          boolean runCleanupThread,
                          boolean runNewThreadForCleanup,
                          ConcurrentLFUCache.EvictionListener<K,V> evictionListener,
                          boolean timeDecay,
                          int maxIdleTimeSec)

ConcurrentLFUCache

public ConcurrentLFUCache(int size,
                          int lowerWatermark)

Method Detail

setAlive

public void setAlive(boolean live)

setUpperWaterMark

public void setUpperWaterMark(int upperWaterMark)

setLowerWaterMark

public void setLowerWaterMark(int lowerWaterMark)

setAcceptableWaterMark

public void setAcceptableWaterMark(int acceptableWaterMark)

setTimeDecay

public void setTimeDecay(boolean timeDecay)

setMaxIdleTime

public void setMaxIdleTime(int maxIdleTime)

setNewThreadForCleanup

public void setNewThreadForCleanup(boolean newThreadForCleanup)

setRunCleanupThread

public void setRunCleanupThread(boolean runCleanupThread)

get

public V get(K key)

Specified by:

get in interface Cache<K,V>

computeIfAbsent

public V computeIfAbsent(K key,
                         Function<? super K,? extends V> mappingFunction)

Specified by:

computeIfAbsent in interface Cache<K,V>

remove

public V remove(K key)

Specified by:

remove in interface Cache<K,V>

put

public V put(K key,
             V val)

Specified by:

put in interface Cache<K,V>

putCacheEntry

public V putCacheEntry(ConcurrentLFUCache.CacheEntry<K,V> e)

Visible for testing to create synthetic cache entries.

NOTE: This API is for internal purposes only and might change in incompatible ways in the next release.

markAndSweep

public void markAndSweep()

Removes items from the cache to bring the size down to the lowerWaterMark.

Visible for unit testing.

NOTE: This API is for internal purposes only and might change in incompatible ways in the next release.

getLeastUsedItems

public Map<K,V> getLeastUsedItems(int n)

Returns 'n' number of least used entries present in this cache.

This uses a TreeSet to collect the 'n' least used items ordered by ascending hitcount and returns a LinkedHashMap containing 'n' or less than 'n' entries.

Parameters:

n - the number of items needed

Returns:

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

getMostUsedItems

public Map<K,V> getMostUsedItems(int n)

Returns 'n' number of most used entries present in this cache.

This uses a TreeSet to collect the 'n' most used items ordered by descending hitcount and returns a LinkedHashMap containing 'n' or less than 'n' entries.

Parameters:

n - the number of items needed

Returns:

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

size

public int size()

clear

public void clear()

Specified by:

clear in interface Cache<K,V>

getMap

public Map<Object,ConcurrentLFUCache.CacheEntry<K,V>> getMap()

ramBytesUsed

public long ramBytesUsed()

Specified by:

ramBytesUsed in interface org.apache.lucene.util.Accountable

destroy

public void destroy()

getStats

public ConcurrentLFUCache.Stats getStats()

finalize

protected void finalize()
                 throws Throwable

Overrides:

finalize in class Object

Throws:

Throwable