Package com.apple.foundationdb.record

Class AsyncLoadingCache<K,V>

java.lang.Object

com.apple.foundationdb.record.AsyncLoadingCache<K,V>

Type Parameters:

K - key type for the cache

V - value type for the cache

@API(UNSTABLE)
public class AsyncLoadingCache<K,V>
extends Object

A cache for retaining the result of some asynchronous operation up until some expiration time.

Field Summary

Fields

Modifier and Type	Field	Description
static long	DEFAULT_DEADLINE_TIME_MILLIS	The default deadline to impose on loading elements.
static long	UNLIMITED	A constant to indicate that an operation should not have a limit.

Constructor Summary

Constructors

Constructor	Description
AsyncLoadingCache(long refreshTimeMillis)
AsyncLoadingCache(long refreshTimeMillis, long deadlineTimeMillis)
AsyncLoadingCache(long refreshTimeMillis, long deadlineTimeMillis, long maxSize)

Method Summary

Modifier and Type	Method	Description
void	clear()
long	getMaxSize()	Get the maximum number of elements stored by the cache.
long	getRefreshTimeSeconds()
CompletableFuture<V>	orElseGet(K key, Supplier<CompletableFuture<V>> supplier)	If the cache does not contain an entry for key, retrieve the value using the provided asynchronous Supplier.
String	toString()

Methods inherited from class java.lang.Object

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

Field Detail

DEFAULT_DEADLINE_TIME_MILLIS

public static final long DEFAULT_DEADLINE_TIME_MILLIS

The default deadline to impose on loading elements.

See Also:

Constant Field Values

UNLIMITED

public static final long UNLIMITED

A constant to indicate that an operation should not have a limit. For example, this can be provided to the cache as the deadline time or the max size to indicate that no deadline should be imposed on futures loading entries into the cache or that there should not be a maximum number of cached elements.

See Also:

Constant Field Values

Constructor Detail

AsyncLoadingCache

public AsyncLoadingCache(long refreshTimeMillis)

AsyncLoadingCache

public AsyncLoadingCache(long refreshTimeMillis,
                         long deadlineTimeMillis)

AsyncLoadingCache

public AsyncLoadingCache(long refreshTimeMillis,
                         long deadlineTimeMillis,
                         long maxSize)

Method Detail

orElseGet

@Nonnull
public CompletableFuture<V> orElseGet(@Nonnull
                                      K key,
                                      @Nonnull
                                      Supplier<CompletableFuture<V>> supplier)

If the cache does not contain an entry for key, retrieve the value using the provided asynchronous Supplier. If the value is not currently cached, then the Supplier is used to load the value asynchronously. If multiple callers ask for the same key at the same time, then they might duplicate each other's work in that both callers will result in a future being created. Whichever future completes first will insert its value into the cache, and all callers that then complete successfully are guaranteed to see that object until such time as the value is expired from the cache.

Parameters:

key - the key in the cache to lookup

supplier - an asynchronous operation to retrieve the desired value if the cache is empty

Returns:

a future containing either the cached value or the result from the supplier

getRefreshTimeSeconds

public long getRefreshTimeSeconds()

getMaxSize

public long getMaxSize()

Get the maximum number of elements stored by the cache. This will return Long.MAX_VALUE if there is no maximum size enforced by this cache.

Returns:

the maximum number of elements stored by the cache

clear

public void clear()

toString

public String toString()

Overrides:

toString in class Object