com.hazelcast.internal.eviction.impl.evaluator.AbstractEvictionPolicyEvaluator Maven / Gradle / Ivy
/*
* Copyright (c) 2008-2016, Hazelcast, Inc. All Rights Reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.hazelcast.internal.eviction.impl.evaluator;
import com.hazelcast.internal.eviction.Evictable;
import com.hazelcast.internal.eviction.EvictionCandidate;
import com.hazelcast.internal.eviction.EvictionPolicyEvaluator;
import com.hazelcast.internal.eviction.Expirable;
import com.hazelcast.util.Clock;
import java.util.Collections;
/**
* Base class for evaluation implementations of {@link com.hazelcast.config.EvictionPolicy}.
*/
public abstract class AbstractEvictionPolicyEvaluator
implements EvictionPolicyEvaluator {
/**
* Compares two evictable candidates and selects one as {@link com.hazelcast.config.EvictionPolicy} rule.
*
* @param current Currently selected evictable candidate
* @param candidate Evictable candidate to compare with current one
*
* @return the selected evictable candidate
*/
protected abstract Evictable selectEvictableAsPolicy(Evictable current, Evictable candidate);
/**
* The evaluate method implements the {@link com.hazelcast.config.EvictionPolicy} rule
* on the given input set of candidates.
*
* @param evictionCandidates Multiple {@link EvictionCandidate} to be evicted
*
* @return multiple {@link EvictionCandidate} these are available to be evicted
*/
@Override
public > Iterable evaluate(Iterable evictionCandidates) {
C evictionCandidate = null;
long now = Clock.currentTimeMillis();
for (C candidate : evictionCandidates) {
if (evictionCandidate == null) {
evictionCandidate = candidate;
} else {
Evictable evictable = candidate.getEvictable();
if (evictable == null) {
continue;
}
if (isExpired(now, evictable)) {
return candidate instanceof Iterable
? (Iterable) candidate
: Collections.singleton(candidate);
}
Evictable selected = selectEvictableAsPolicy(evictionCandidate.getEvictable(), evictable);
if (selected == evictable) {
evictionCandidate = candidate;
}
}
}
if (evictionCandidate == null) {
return null;
} else {
return evictionCandidate instanceof Iterable
? (Iterable) evictionCandidate
: Collections.singleton(evictionCandidate);
}
}
private boolean isExpired(long now, Evictable evictable) {
// If evictable is also an expirable
if (evictable instanceof Expirable) {
Expirable expirable = (Expirable) evictable;
// If there is an expired candidate, let's evict that one immediately
return expirable.isExpiredAt(now);
}
return false;
}
}