com.yahoo.prelude.cache

Class Cache<K,V>

java.lang.Object

com.yahoo.prelude.cache.Cache<K,V>

public class Cache<K,V>
extends Object

A generic cache which keeps the total memory consumed by its content below a configured maximum.

Thread safe.

Author:

vegardh

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
private static class	Cache.AgingCacheValue<K,V>
private static class	Cache.CacheKey<K>
private static class	Cache.CacheValue<K,V>

Field Summary

Fields

Modifier and Type	Field and Description
private com.yahoo.cache.SizeCalculator	calc
private Map<Cache.CacheKey<K>,Cache.CacheValue<K,V>>	content
private long	currentSizeBytes
private com.yahoo.statistics.Value	elems
private com.yahoo.statistics.Value	entrySizes
private long	maxEntrySizeBytes The max allowed size of an entry
private long	maxSizeBytes
private long	timeToLiveMillis The time an element is allowed to live, negative for indefinite lifespan

Constructor Summary

Constructors

Constructor and Description
Cache(long maxSizeBytes, long timeToLiveMillis, long maxEntrySizeBytes, com.yahoo.statistics.Statistics manager) Creates a new cache

Method Summary

Modifier and Type	Method and Description
boolean	containsKey(K k)
V	get(K key) Returns a value, if it is present in the cache
private void	initStats(com.yahoo.statistics.Statistics manager)
private void	makeRoomForBytes(long bytes)
boolean	put(K key, V value) Attempts to add a value to the cache
boolean	remove(K key) Removes a cache value if present
int	size()
private Cache.CacheValue<K,V>	synchGet(Cache.CacheKey<K> k)
private boolean	synchPut(K key, V value, long keySizeBytes, long valueSizeBytes)
private boolean	tooBigToCache(long totalSize) Don't cache elems that are too big, even if there's space

Methods inherited from class java.lang.Object

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

Field Detail

elems

private com.yahoo.statistics.Value elems

entrySizes

private com.yahoo.statistics.Value entrySizes

content

private Map<Cache.CacheKey<K>,Cache.CacheValue<K,V>> content

calc

private com.yahoo.cache.SizeCalculator calc

maxSizeBytes

private long maxSizeBytes

currentSizeBytes

private long currentSizeBytes

timeToLiveMillis

private long timeToLiveMillis

The time an element is allowed to live, negative for indefinite lifespan

maxEntrySizeBytes

private long maxEntrySizeBytes

The max allowed size of an entry

Constructor Detail

Cache

public Cache(long maxSizeBytes,
             long timeToLiveMillis,
             long maxEntrySizeBytes,
             com.yahoo.statistics.Statistics manager)

Creates a new cache

Parameters:

maxSizeBytes - the max size in bytes this cache is permitted to consume, including Result objects and Query keys

timeToLiveMillis - a negative value means unlimited time

manager - the current Statistics manager acquired by injection

Method Detail

initStats

private void initStats(com.yahoo.statistics.Statistics manager)

synchGet

private Cache.CacheValue<K,V> synchGet(Cache.CacheKey<K> k)

synchPut

private boolean synchPut(K key,
                         V value,
                         long keySizeBytes,
                         long valueSizeBytes)

put

public boolean put(K key,
                   V value)

Attempts to add a value to the cache

Parameters:

key - the key of the value

value - the value to add

Returns:

true if the value was added, false if it could not be added

tooBigToCache

private boolean tooBigToCache(long totalSize)

Don't cache elems that are too big, even if there's space

makeRoomForBytes

private void makeRoomForBytes(long bytes)

containsKey

public boolean containsKey(K k)

get

public V get(K key)

Returns a value, if it is present in the cache

remove

public boolean remove(K key)

Removes a cache value if present

Returns:

true if the value was removed, false if it was not present

size

public int size()