com.trivago.triava.tcache.eviction

Interface EvictionInterface<K,V>

Type Parameters:

K - Key class

V - Value class

All Superinterfaces:

Serializable

All Known Implementing Classes:

ClockEviction, FreezingEvictor, LFUEviction, LRUEviction

public interface EvictionInterface<K,V>
extends Serializable

Eviction interface, that can operate on 4 values: Meta data, key, value and a "frozen value". Values that could change during an eviction run (like use count) must be "frozen" instead of used directly. Typical implementations will extend FreezingEvictor instead of directly implementing EvictionInterface, as the former already implements the evictionComparator().

Any EvictionInterface implementation must be Serializable, as it is part of the cache configuration, and any Configuration must be Serializable as configurations must be able to be transferred over the network to remote instances.

Author:

cesken

Method Summary

Modifier and Type	Method and Description
void	afterEviction() Called each time after an eviction cycle has ended.
void	beforeEviction() Called each time before an eviction cycle is being started.
Comparator<? super HolderFreezer<K,V>>	evictionComparator() Returns the Comparator implementing the eviction policy.
long	getFreezeValue(K key, TCacheHolder<V> holder) Returns a value that is required by the actual implementation for eviction.

Method Detail

evictionComparator

Comparator<? super HolderFreezer<K,V>> evictionComparator()

Returns the Comparator implementing the eviction policy. Elements to be evicted earlier have to be sorted to the front by the returned Comparator.

Returns:

The comparator implementing the eviction policy

getFreezeValue

long getFreezeValue(K key,
                    TCacheHolder<V> holder)

Returns a value that is required by the actual implementation for eviction. Implement this if you rely on a value that may change over the course of the eviction sorting process. Examples of changing values are the usage count or the last use timestamp.

TODO For v2.0: First, rename this to getSnapshot() as it is clearer. Secondly, we could allow snapshots to be objects, and then we would have "public interface EvictionInterface<K, V, SNAPSHOT>"

Parameters:

key - The key of the cache entry

holder - The holder, which includes the value and metadata

Returns:

The snapshot of the value

beforeEviction

void beforeEviction()

Called each time before an eviction cycle is being started.

afterEviction

void afterEviction()

Called each time after an eviction cycle has ended.