org.apache.reef.util.cache

Class CacheImpl<K,V>

java.lang.Object

org.apache.reef.util.cache.CacheImpl<K,V>

All Implemented Interfaces:

Cache<K,V>

public final class CacheImpl<K,V>
extends Object
implements Cache<K,V>

Implementation that supports expire-after-write. Entries that have expired are collected and invalidated on get calls. This obviates the need for a separate thread to invalidate expired entries, at the cost of some increase in get call latency. The invalidation sweep is only initiated after an interval (expireCheckInterval) has passed, and at most one invalidation sweep is run at a time. Operations on a single key are linearizable. The argument is: 1. The putIfAbsent call in get guarantees that loadAndGet is called exactly once for a WrappedValue instance that is put into the map: All putIfAbsent calls that return the WrappedValue instance will return the value loaded by loadAndGet. 2. Concurrent putIfAbsent and remove calls on a key have an ordering: if putIfAbsent returns null then it happened after the remove (and a new value will be loaded); else if it returns non-null then it happened before the remove (and the previous value will be returned).

Constructor Summary

Constructors

Constructor and Description
CacheImpl(CurrentTime currentTime, long timeoutMillis) Construct an expire-after-write cache.

Method Summary

Modifier and Type	Method and Description
V	get(K key, Callable<V> valueFetcher) Returns a value for the key if cached; otherwise creates, caches and returns.
void	invalidate(K key) Invalidates a key from the cache.

Methods inherited from class java.lang.Object

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

Constructor Detail

CacheImpl

@Inject
public CacheImpl(CurrentTime currentTime,
                         long timeoutMillis)

Construct an expire-after-write cache.

Parameters:

currentTime - class that returns the current time for timeout purposes

timeoutMillis - a cache entry timeout after write

Method Detail

get

public V get(K key,
             Callable<V> valueFetcher)
      throws ExecutionException

Description copied from interface: Cache

Returns a value for the key if cached; otherwise creates, caches and returns. When it creates a value for a key, only one callable for the key is executed

Specified by:

get in interface Cache<K,V>

Parameters:

key - a key

valueFetcher - a value fetcher

Returns:

a value

Throws:

ExecutionException

invalidate

public void invalidate(K key)

Description copied from interface: Cache

Invalidates a key from the cache.

Specified by:

invalidate in interface Cache<K,V>

Parameters:

key - a key