hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/impl/prefetch/PrefetchingStatistics.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.hadoop.fs.impl.prefetch;

import java.time.Duration;

import org.apache.hadoop.fs.statistics.DurationTracker;
import org.apache.hadoop.fs.statistics.IOStatisticsSource;

public interface PrefetchingStatistics extends IOStatisticsSource {

  /**
   * A prefetch operation has started.
   * @return duration tracker
   */
  DurationTracker prefetchOperationStarted();

  /**
   * A block has been saved to the file cache.
   */
  void blockAddedToFileCache();

  /**
   * A block has been removed from the file cache.
   */
  void blockRemovedFromFileCache();

  /**
   * A prefetch operation has completed.
   */
  void prefetchOperationCompleted();

  /**
   * An executor has been acquired, either for prefetching or caching.
   * @param timeInQueue time taken to acquire an executor.
   */
  void executorAcquired(Duration timeInQueue);

  /**
   * A new buffer has been added to the buffer pool.
   * @param size size of the new buffer
   */
  void memoryAllocated(int size);

  /**
   * Previously allocated memory has been freed.
   * @param size size of memory freed.
   */
  void memoryFreed(int size);
}