io.druid.server.lookup.cache.loading

Interface LoadingCache<K,V>

All Superinterfaces:

AutoCloseable, Closeable

All Known Implementing Classes:

OffHeapLoadingCache, OnHeapLoadingCache

public interface LoadingCache<K,V>
extends Closeable

A semi-persistent mapping from keys to values. Cache entries are added using get(Object, Callable) and stored in the cache until either evicted or manually invalidated.

Implementations of this interface are expected to be thread-safe, and can be safely accessed by multiple concurrent threads. This interface borrows ideas (and in some cases methods and javadoc) from Guava and JCache cache interface. Thanks Guava and JSR ! We elected to make this as close as possible to JSR API like that users can build bridges between all the existing implementations of JSR.

Method Summary

Modifier and Type	Method and Description
void	close() Clean the used resources of the cache.
V	get(K key, Callable<? extends V> valueLoader) Returns the value associated with key in this cache, obtaining that value from valueLoader if necessary.
Map<K,V>	getAllPresent(Iterable<K> keys) Returns a map of the values associated with keys in this cache.
V	getIfPresent(K key)
LookupCacheStats	getStats()
void	invalidate(K key) Discards any cached value for key key.
void	invalidateAll() Clears the contents of the cache.
void	invalidateAll(Iterable<K> keys) Discards any cached values for keys keys.
boolean	isClosed()
void	putAll(Map<? extends K,? extends V> m) Copies all of the mappings from the specified map to the cache.

Method Detail

getIfPresent

@Nullable
V getIfPresent(K key)

Parameters:

key - must not be null Returns the value associated with key in this cache, or null if there is no cached value for key. a cache miss should be counted if the key is missing.

getAllPresent

Map<K,V> getAllPresent(Iterable<K> keys)

Returns a map of the values associated with keys in this cache. The returned map will only contain entries which are already present in the cache.

get

V get(K key,
      Callable<? extends V> valueLoader)
throws ExecutionException

Returns the value associated with key in this cache, obtaining that value from valueLoader if necessary. No observable state associated with this cache is modified until loading completes.

Warning: as with CacheLoader.load(K), valueLoader must not return null; it may either return a non-null value or throw an exception.

Throws:

ExecutionException - if a checked exception was thrown while loading the value

com.google.common.util.concurrent.UncheckedExecutionException - if an unchecked exception was thrown while loading the value

com.google.common.util.concurrent.ExecutionError - if an error was thrown while loading the value

putAll

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

Copies all of the mappings from the specified map to the cache. This method is used for bulk put.

Throws:

IllegalStateException - if the cache is isClosed()

invalidate

void invalidate(K key)

Discards any cached value for key key. Eviction can be lazy or eager.

Throws:

IllegalStateException - if the cache is isClosed()

invalidateAll

void invalidateAll(Iterable<K> keys)

Discards any cached values for keys keys. Eviction can be lazy or eager.

Throws:

IllegalStateException - if the cache is isClosed()

invalidateAll

void invalidateAll()

Clears the contents of the cache.

Throws:

IllegalStateException - if the cache is isClosed()

getStats

LookupCacheStats getStats()

Returns:

Stats of the cache.

Throws:

IllegalStateException - if the cache is isClosed()

isClosed

boolean isClosed()

Returns:

true if the Cache is closed

close

void close()

Clean the used resources of the cache. Still not sure about cache lifecycle but as an initial design the namespace deletion event should call this method to clean up resources.

Specified by:

close in interface AutoCloseable

Specified by:

close in interface Closeable