alluxio-master-2.x/core/client/fs/src/main/java/alluxio/client/file/cache/evictor/CacheEvictor.java
/*
 * The Alluxio Open Foundation licenses this work under the Apache License, version 2.0
 * (the "License"). You may not use this work except in compliance with the License, which is
 * available at www.apache.org/licenses/LICENSE-2.0
 *
 * This software is distributed on an "AS IS" basis, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
 * either express or implied, as more fully set forth in the License.
 *
 * See the NOTICE file distributed with this work for information regarding copyright ownership.
 */

package alluxio.client.file.cache.evictor;

import alluxio.client.file.cache.PageId;
import alluxio.util.CommonUtils;

import java.util.function.Predicate;
import javax.annotation.Nullable;
import javax.annotation.concurrent.ThreadSafe;

/**
 * Interface for client-side cache eviction policy. The implementation of this evictor must be
 * thread-safe.
 */
@ThreadSafe
public interface CacheEvictor {

  /**
   * @param options cache evictor options
   * @return a CacheEvictor instance
   */
  static CacheEvictor create(CacheEvictorOptions options) {
    if (options.isNondeterministic() && options.getEvictorClass().equals(LRUCacheEvictor.class)) {
      return new NondeterministicLRUCacheEvictor(options);
    }
    return CommonUtils.createNewClassInstance(
        options.getEvictorClass(),
        new Class[] {CacheEvictorOptions.class}, new Object[] {options});
  }

  /**
   * Updates evictor after a get operation.
   *
   * @param pageId page identifier
   */
  void updateOnGet(PageId pageId);

  /**
   * Updates evictor after a put operation.
   *
   * @param pageId page identifier
   */
  void updateOnPut(PageId pageId);

  /**
   * Updates evictor after a delete operation.
   *
   * @param pageId page identifier
   */
  void updateOnDelete(PageId pageId);

  /**
   * @return a page to evict or null if no page available to evict
   */
  @Nullable
  PageId evict();

  /**
   * Picks the first candidate for eviction that satisfies the given criterion.
   *
   * @param criterion criterion
   * @return the eviction candidate, or null if none
   */
  @Nullable
  PageId evictMatching(Predicate<PageId> criterion);

  /**
   * Resets the evictor.
   */
  void reset();
}
