org.mapdb

Class LongConcurrentLRUMap<V>

java.lang.Object

org.mapdb.LongMap<V>

org.mapdb.LongConcurrentLRUMap<V>

public class LongConcurrentLRUMap<V>
extends LongMap<V>

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. MapDB note: reworked to implement LongMap. Original comes from: https://svn.apache.org/repos/asf/lucene/dev/trunk/solr/core/src/java/org/apache/solr/util/ConcurrentLRUCache.java

Nested Class Summary

Nested classes/interfaces inherited from class org.mapdb.LongMap

LongMap.LongMapIterator<V>

Field Summary

Fields

Modifier and Type	Field and Description
protected int	acceptableWaterMark
protected AtomicLong	accessCounter
protected AtomicLong	evictionCounter
protected boolean	isCleaning
protected int	lowerWaterMark
protected LongConcurrentHashMap<org.mapdb.LongConcurrentLRUMap.CacheEntry<V>>	map
protected ReentrantLock	markAndSweepLock
protected AtomicLong	missCounter
protected long	oldestEntry
protected AtomicLong	putCounter
protected AtomicInteger	size
protected int	upperWaterMark

Constructor Summary

Constructors

Constructor and Description
LongConcurrentLRUMap(int size, int lowerWatermark)
LongConcurrentLRUMap(int upperWaterMark, int lowerWaterMark, int acceptableWatermark, int initialSize)

Method Summary

Modifier and Type	Method and Description
void	clear() Removes all mappings from this hash map, leaving it empty.
protected void	evictedEntry(long key, V value) override this method to get notified about evicted entries
V	get(long key) Returns the value of the mapping with the specified key.
LongMap<org.mapdb.LongConcurrentLRUMap.CacheEntry<V>>	getMap()
boolean	isEmpty() Returns whether this map is empty.
LongMap.LongMapIterator<V>	longMapIterator()
V	put(long key, V val) Maps the specified key to the specified value.
V	remove(long key) Removes the mapping from this map
int	size() Returns the number of elements in this map.
Iterator<V>	valuesIterator()

Methods inherited from class org.mapdb.LongMap

toString

Methods inherited from class java.lang.Object

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

Field Detail

map

protected final LongConcurrentHashMap<org.mapdb.LongConcurrentLRUMap.CacheEntry<V>> map

upperWaterMark

protected final int upperWaterMark

lowerWaterMark

protected final int lowerWaterMark

markAndSweepLock

protected final ReentrantLock markAndSweepLock

isCleaning

protected boolean isCleaning

acceptableWaterMark

protected final int acceptableWaterMark

oldestEntry

protected long oldestEntry

accessCounter

protected final AtomicLong accessCounter

putCounter

protected final AtomicLong putCounter

missCounter

protected final AtomicLong missCounter

evictionCounter

protected final AtomicLong evictionCounter

size

protected final AtomicInteger size

Constructor Detail

LongConcurrentLRUMap

public LongConcurrentLRUMap(int upperWaterMark,
                            int lowerWaterMark,
                            int acceptableWatermark,
                            int initialSize)

LongConcurrentLRUMap

public LongConcurrentLRUMap(int size,
                            int lowerWatermark)

Method Detail

get

public V get(long key)

Description copied from class: LongMap

Returns the value of the mapping with the specified key.

Specified by:

get in class LongMap<V>

Parameters:

key - the key.

Returns:

the value of the mapping with the specified key, or null if no mapping for the specified key is found.

isEmpty

public boolean isEmpty()

Description copied from class: LongMap

Returns whether this map is empty.

Specified by:

isEmpty in class LongMap<V>

Returns:

true if this map has no elements, false otherwise.

See Also:

LongMap.size()

remove

public V remove(long key)

Description copied from class: LongMap

Removes the mapping from this map

Specified by:

remove in class LongMap<V>

Parameters:

key - to remove

Returns:

value contained under this key, or null if value did not exist

put

public V put(long key,
             V val)

Description copied from class: LongMap

Maps the specified key to the specified value.

Specified by:

put in class LongMap<V>

Parameters:

key - the key.

val - the value.

Returns:

the value of any previous mapping with the specified key or null if there was no such mapping.

size

public int size()

Description copied from class: LongMap

Returns the number of elements in this map.

Specified by:

size in class LongMap<V>

Returns:

the number of elements in this map.

valuesIterator

public Iterator<V> valuesIterator()

Specified by:

valuesIterator in class LongMap<V>

Returns:

iterator over values in map

longMapIterator

public LongMap.LongMapIterator<V> longMapIterator()

Specified by:

longMapIterator in class LongMap<V>

clear

public void clear()

Description copied from class: LongMap

Removes all mappings from this hash map, leaving it empty.

Specified by:

clear in class LongMap<V>

See Also:

LongMap.isEmpty(), LongMap.size()

getMap

public LongMap<org.mapdb.LongConcurrentLRUMap.CacheEntry<V>> getMap()

evictedEntry

protected void evictedEntry(long key,
                            V value)

override this method to get notified about evicted entries