/*
 * 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 static org.apache.hadoop.fs.statistics.IOStatisticsSupport.stubDurationTracker;

/**
 * Empty implementation of the prefetching statistics interface.
 */
public final class EmptyPrefetchingStatistics
    implements PrefetchingStatistics {

  private static final EmptyPrefetchingStatistics
      EMPTY_PREFETCHING_STATISTICS =
      new EmptyPrefetchingStatistics();

  private EmptyPrefetchingStatistics() {
  }

  public static EmptyPrefetchingStatistics getInstance() {
    return EMPTY_PREFETCHING_STATISTICS;
  }

  @Override
  public DurationTracker prefetchOperationStarted() {
    return stubDurationTracker();
  }

  @Override
  public void blockAddedToFileCache() {

  }

  @Override
  public void blockRemovedFromFileCache() {

  }

  @Override
  public void prefetchOperationCompleted() {

  }

  @Override
  public void executorAcquired(Duration timeInQueue) {

  }

  @Override
  public void memoryAllocated(int size) {

  }

  @Override
  public void memoryFreed(int size) {

  }
}

