modules/core/src/main/java/org/apache/ignite/cache/eviction/lru/LruEvictionPolicyFactory.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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 org.apache.ignite.cache.eviction.lru;

import org.apache.ignite.cache.eviction.AbstractEvictionPolicyFactory;

/**
 * Factory class for {@link LruEvictionPolicy}.
 *
 * Creates cache Eviction policy based on {@code Least Recently Used (LRU)} algorithm and supports batch eviction.
 * <p>
 * The eviction starts in the following cases:
 * <ul>
 *     <li>The cache size becomes {@code batchSize} elements greater than the maximum size.</li>
 *     <li>
 *         The size of cache entries in bytes becomes greater than the maximum memory size.
 *         The size of cache entry calculates as sum of key size and value size.
 *     </li>
 * </ul>
 * <b>Note:</b>Batch eviction is enabled only if maximum memory limit isn't set ({@code maxMemSize == 0}).
 * {@code batchSize} elements will be evicted in this case. The default {@code batchSize} value is {@code 1}.

 *  {@link LruEvictionPolicy} implementation is very efficient since it is lock-free and does not create any additional table-like
 * data structures. The {@code LRU} ordering information is maintained by attaching ordering metadata to cache entries.
 */
public class LruEvictionPolicyFactory<K, V> extends AbstractEvictionPolicyFactory<LruEvictionPolicy<K, V>> {
    /** */
    private static final long serialVersionUID = 0L;

    /** */
    public LruEvictionPolicyFactory() {
    }

    /** @param maxSize Maximum allowed size of cache before entry will start getting evicted. */
    public LruEvictionPolicyFactory(int maxSize) {
        setMaxSize(maxSize);
    }

    /**
     * @param maxSize Maximum allowed size of cache before entry will start getting evicted.
     * @param batchSize Batch size.
     * @param maxMemSize Maximum allowed cache size in bytes.
     */
    public LruEvictionPolicyFactory(int maxSize, int batchSize, long maxMemSize) {
        setMaxSize(maxSize);
        setBatchSize(batchSize);
        setMaxMemorySize(maxMemSize);
    }

    /** {@inheritDoc} */
    @Override public LruEvictionPolicy<K, V> create() {
        LruEvictionPolicy<K, V> policy = new LruEvictionPolicy<>();

        policy.setBatchSize(getBatchSize());
        policy.setMaxMemorySize(getMaxMemorySize());
        policy.setMaxSize(getMaxSize());

        return policy;
    }
}