content: /*
   * 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.
   */
  
  /**
   * Set of evictors for evicting or moving blocks to other locations.
   *
   * The main entry point is {@link alluxio.worker.block.evictor.Evictor} which returns an evictor by
   * calling alluxio.worker.block.Evictor.Factory#create.
   *
   * <h2>Evictor</h2>
   *
   * All evictors implement {@link alluxio.worker.block.evictor.Evictor} interface. In order to evict
   * blocks by different policies, each evictor only need to implement
   * {@link alluxio.worker.block.evictor.Evictor#freeSpaceWithView(long,
   * alluxio.worker.block.BlockStoreLocation, alluxio.worker.block.BlockMetadataEvictorView)}
   * method. When this method is called, blocks will be evicted or moved if no enough space left.
   *
   * <h3>Cascading Eviction</h3> Cascading Eviction means evict blocks recursively and is only called
   * in {@link alluxio.worker.block.evictor.Evictor#freeSpaceWithView(long,
   * alluxio.worker.block.BlockStoreLocation, alluxio.worker.block.BlockMetadataEvictorView)}
   * method. Cascading Eviction will try to free space in next tier view where blocks need to be
   * transferred to, if the next tier view does not have enough free space to hold the blocks, the
   * next next tier view will be tried and so on until the bottom tier is reached, if blocks can not
   * even be transferred to the bottom tier, they will be evicted, otherwise, only blocks to be freed
   * in the bottom tier will be evicted.
   *
   * For example,
   * {@link alluxio.worker.block.evictor.LRUEvictor#cascadingEvict(long,
   * alluxio.worker.block.BlockStoreLocation,EvictionPlan)}
   * is an implementation of Cascading Eviction.
   *
   * <h3>Eviction Plan</h3>
   *
   * Eviction plan will be returned when
   * {@link alluxio.worker.block.evictor.Evictor#freeSpaceWithView(long,
   * alluxio.worker.block.BlockStoreLocation, alluxio.worker.block.BlockMetadataEvictorView)}
   * is called. The eviction plan will return two block lists, one is the blocks to be removed
   * directly and another is the blocks to be moved to lower tier views.
   */
  
  package alluxio.worker.block.evictor;
  