org.apache.hadoop.hbase.regionserver

类 LruHashMap<K extends HeapSize,V extends HeapSize>

java.lang.Object

org.apache.hadoop.hbase.regionserver.LruHashMap<K,V>

所有已实现的接口:

Map<K,V>, HeapSize

@InterfaceAudience.Private
public class LruHashMap<K extends HeapSize,V extends HeapSize>
extends Object
implements HeapSize, Map<K,V>

The LruHashMap is a memory-aware HashMap with a configurable maximum memory footprint.

It maintains an ordered list of all entries in the/ map ordered by access time. When space needs to be freed becase the maximum has been reached, or the application has asked to free memory, entries will be evicted according to an LRU (least-recently-used) algorithm. That is, those entries which have not been accessed the longest will be evicted first.

Both the Key and Value Objects used for this class must extend HeapSize in order to track heap usage.

This class contains internal synchronization and is thread-safe.

嵌套类概要

嵌套类

限定符和类型	类和说明
protected static class	LruHashMap.Entry<K extends HeapSize,V extends HeapSize> Entry to store key/value mappings.

构造器概要

构造器

构造器和说明
LruHashMap() Constructs a new, empty map with the default initial capacity, load factor and maximum memory usage.
LruHashMap(int initialCapacity) Constructs a new, empty map with the specified initial capacity and with the default load factor and maximum memory usage.
LruHashMap(int initialCapacity, float loadFactor) Constructs a new, empty map with the specified initial capacity and load factor, and default maximum memory usage.
LruHashMap(int initialCapacity, float loadFactor, long maxMemUsage) Constructs a new, empty map with the specified initial capacity, load factor, and maximum memory usage.
LruHashMap(long maxMemUsage) Constructs a new, empty map with the specified maximum memory usage and with default initial capacity and load factor.

方法概要

方法

限定符和类型	方法和说明
void	clear() Clears all entries from the map.
boolean	containsKey(Object key) Checks whether there is a value in the map for the specified key.
boolean	containsValue(Object value) Checks whether this is a mapping which contains the specified value.
List<LruHashMap.Entry<K,V>>	entryLruList() Debugging function that returns a List sorted by access time.
Set<Map.Entry<K,V>>	entrySet() Intentionally unimplemented.
Set<LruHashMap.Entry<K,V>>	entryTableSet() Debugging function that returns a Set of all entries in the hash table.
boolean	equals(Object o) Intentionally unimplemented.
long	freeMemory(long requestedAmount) Free the requested amount of memory from the LRU map.
V	get(Object key) Retrieves the value associated with the specified key.
LruHashMap.Entry	getHeadPtr() Get the head of the linked list (least recently used).
long	getHitCount() Get the number of hits to the map.
double	getHitRatio() Get the hit ratio.
long	getMemFree() Get the currently available memory for this LRU in bytes.
long	getMemMax() Get the maximum memory allowed for this LRU in bytes.
long	getMemUsed() Get the currently used memory for this LRU in bytes.
long	getMissCount() Get the number of misses to the map.
LruHashMap.Entry	getTailPtr() Get the tail of the linked list (most recently used).
int	hashCode() Intentionally unimplemented.
long	heapSize() The total memory usage of this map
boolean	isEmpty() Checks whether the map is currently empty.
Set<K>	keySet() Intentionally unimplemented.
V	put(K key, V value) Insert a key-value mapping into the map.
void	putAll(Map<? extends K,? extends V> m) Intentionally unimplemented.
V	remove(Object key) Deletes the mapping for the specified key if it exists.
int	size() Gets the size (number of entries) of the map.
Collection<V>	values() Intentionally unimplemented.

从类继承的方法 java.lang.Object

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

构造器详细资料

LruHashMap

public LruHashMap(int initialCapacity,
          float loadFactor,
          long maxMemUsage)

Constructs a new, empty map with the specified initial capacity, load factor, and maximum memory usage.

参数:

initialCapacity - the initial capacity

loadFactor - the load factor

maxMemUsage - the maximum total memory usage

抛出:

IllegalArgumentException - if the initial capacity is less than one

IllegalArgumentException - if the initial capacity is greater than the maximum capacity

IllegalArgumentException - if the load factor is <= 0

IllegalArgumentException - if the max memory usage is too small to support the base overhead

LruHashMap

public LruHashMap(int initialCapacity,
          float loadFactor)

Constructs a new, empty map with the specified initial capacity and load factor, and default maximum memory usage.

参数:

initialCapacity - the initial capacity

loadFactor - the load factor

抛出:

IllegalArgumentException - if the initial capacity is less than one

IllegalArgumentException - if the initial capacity is greater than the maximum capacity

IllegalArgumentException - if the load factor is <= 0

LruHashMap

public LruHashMap(int initialCapacity)

Constructs a new, empty map with the specified initial capacity and with the default load factor and maximum memory usage.

参数:

initialCapacity - the initial capacity

抛出:

IllegalArgumentException - if the initial capacity is less than one

IllegalArgumentException - if the initial capacity is greater than the maximum capacity

LruHashMap

public LruHashMap(long maxMemUsage)

Constructs a new, empty map with the specified maximum memory usage and with default initial capacity and load factor.

参数:

maxMemUsage - the maximum total memory usage

抛出:

IllegalArgumentException - if the max memory usage is too small to support the base overhead

LruHashMap

public LruHashMap()

Constructs a new, empty map with the default initial capacity, load factor and maximum memory usage.

方法详细资料

getMemFree

public long getMemFree()

Get the currently available memory for this LRU in bytes. This is (maxAllowed - currentlyUsed).

返回:

currently available bytes

getMemMax

public long getMemMax()

Get the maximum memory allowed for this LRU in bytes.

返回:

maximum allowed bytes

getMemUsed

public long getMemUsed()

Get the currently used memory for this LRU in bytes.

返回:

currently used memory in bytes

getHitCount

public long getHitCount()

Get the number of hits to the map. This is the number of times a call to get() returns a matched key.

返回:

number of hits

getMissCount

public long getMissCount()

Get the number of misses to the map. This is the number of times a call to get() returns null.

返回:

number of misses

getHitRatio

public double getHitRatio()

Get the hit ratio. This is the number of hits divided by the total number of requests.

返回:

hit ratio (double between 0 and 1)

freeMemory

public long freeMemory(long requestedAmount)
                throws Exception

Free the requested amount of memory from the LRU map. This will do LRU eviction from the map until at least as much memory as requested is freed. This does not affect the maximum memory usage parameter.

参数:

requestedAmount - memory to free from LRU in bytes

返回:

actual amount of memory freed in bytes

抛出:

Exception

heapSize

public long heapSize()

The total memory usage of this map

指定者:

heapSize 在接口中 HeapSize

返回:

memory usage of map in bytes

get

public V get(Object key)

Retrieves the value associated with the specified key. If an entry is found, it is updated in the LRU as the most recently used (last to be evicted) entry in the map.

指定者:

get 在接口中 Map<K extends HeapSize,V extends HeapSize>

参数:

key - the key

返回:

the associated value, or null if none found

抛出:

NullPointerException - if key is null

put

public V put(K key,
    V value)

Insert a key-value mapping into the map. Entry will be inserted as the most recently used. Both the key and value are required to be Objects and must implement the HeapSize interface.

指定者:

put 在接口中 Map<K extends HeapSize,V extends HeapSize>

参数:

key - the key

value - the value

返回:

the value that was previously mapped to this key, null if none

抛出:

UnsupportedOperationException - if either objects do not implement HeapSize

NullPointerException - if the key or value is null

remove

public V remove(Object key)

Deletes the mapping for the specified key if it exists.

指定者:

remove 在接口中 Map<K extends HeapSize,V extends HeapSize>

参数:

key - the key of the entry to be removed from the map

返回:

the value associated with the specified key, or null if no mapping exists.

size

public int size()

Gets the size (number of entries) of the map.

指定者:

size 在接口中 Map<K extends HeapSize,V extends HeapSize>

返回:

size of the map

isEmpty

public boolean isEmpty()

Checks whether the map is currently empty.

指定者:

isEmpty 在接口中 Map<K extends HeapSize,V extends HeapSize>

返回:

true if size of map is zero

clear

public void clear()

Clears all entries from the map. This frees all entries, tracking memory usage along the way. All references to entries are removed so they can be GC'd.

指定者:

clear 在接口中 Map<K extends HeapSize,V extends HeapSize>

containsKey

public boolean containsKey(Object key)

Checks whether there is a value in the map for the specified key. Does not affect the LRU.

指定者:

containsKey 在接口中 Map<K extends HeapSize,V extends HeapSize>

参数:

key - the key to check

返回:

true if the map contains a value for this key, false if not

抛出:

NullPointerException - if the key is null

containsValue

public boolean containsValue(Object value)

Checks whether this is a mapping which contains the specified value. Does not affect the LRU. This is an inefficient operation.

指定者:

containsValue 在接口中 Map<K extends HeapSize,V extends HeapSize>

参数:

value - the value to check

返回:

true if the map contains an entry for this value, false if not

抛出:

NullPointerException - if the value is null

entryLruList

public List<LruHashMap.Entry<K,V>> entryLruList()

Debugging function that returns a List sorted by access time. The order is oldest to newest (first in list is next to be evicted).

返回:

Sorted list of entries

entryTableSet

public Set<LruHashMap.Entry<K,V>> entryTableSet()

Debugging function that returns a Set of all entries in the hash table.

返回:

Set of entries in hash

getHeadPtr

public LruHashMap.Entry getHeadPtr()

Get the head of the linked list (least recently used).

返回:

head of linked list

getTailPtr

public LruHashMap.Entry getTailPtr()

Get the tail of the linked list (most recently used).

返回:

tail of linked list

entrySet

public Set<Map.Entry<K,V>> entrySet()

Intentionally unimplemented.

指定者:

entrySet 在接口中 Map<K extends HeapSize,V extends HeapSize>

equals

public boolean equals(Object o)

Intentionally unimplemented.

指定者:

equals 在接口中 Map<K extends HeapSize,V extends HeapSize>

覆盖:

equals 在类中 Object

hashCode

public int hashCode()

Intentionally unimplemented.

指定者:

hashCode 在接口中 Map<K extends HeapSize,V extends HeapSize>

覆盖:

hashCode 在类中 Object

keySet

public Set<K> keySet()

Intentionally unimplemented.

指定者:

keySet 在接口中 Map<K extends HeapSize,V extends HeapSize>

putAll

public void putAll(Map<? extends K,? extends V> m)

Intentionally unimplemented.

指定者:

putAll 在接口中 Map<K extends HeapSize,V extends HeapSize>

values

public Collection<V> values()

Intentionally unimplemented.

指定者:

values 在接口中 Map<K extends HeapSize,V extends HeapSize>