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.
   */
  
  package alluxio.worker.block.annotator;
  
  import alluxio.annotation.PublicApi;
  import alluxio.collections.Pair;
  import alluxio.conf.Configuration;
  import alluxio.conf.PropertyKey;
  import alluxio.util.CommonUtils;
  
  import java.util.List;
  import javax.annotation.concurrent.ThreadSafe;
  
  /**
   * Interface for providers that annotates blocks for sorting.
   *
   * @param <T> sorted-field type for the annotator
   */
  @PublicApi
  public interface BlockAnnotator<T extends BlockSortedField> {
  
    /**
     * Factory for {@link BlockAnnotator}.
     */
    @ThreadSafe
    class Factory {
      private Factory() {} // prevent instantiation
  
      /**
       * Creates {@link BlockAnnotator} implementation based
       * on Alluxio configuration.
       *
       * @return the generated {@link BlockAnnotator} instance
       */
      public static BlockAnnotator create() {
        return CommonUtils.createNewClassInstance(
            Configuration.getClass(PropertyKey.WORKER_BLOCK_ANNOTATOR_CLASS), null,
            null);
      }
    }
  
    /**
     * Used to get a new sorted-field for the given block
     * at the current logical time.
     *
     * @param blockId block Id
     * @param oldValue old sorted-field value
     * @return the new sorted-field value
     */
    BlockSortedField updateSortedField(long blockId, T oldValue);
  
    /**
     * Updates sorted-field values for all {block-id, sorted-field} pairs
     * at the same logical time.
     * Note: Currently not required for online schemes, so not called.
     *
     * @param blockList list of {block-id, sorted-field} pairs
     */
    void updateSortedFields(List<Pair<Long, T>> blockList);
  
    /**
     * Used to report whether the block annotator is an online sorter.
     *
     * For offline sorters, {@link #updateSortedFields(List)} will be called before
     * acquiring an iterator for a particular location.
     *
     * @return {@code true} if an online sorter
     */
    boolean isOnlineSorter();
  }
  