001/**
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *     http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018
019package org.apache.hadoop.metrics2.lib;
020
021import org.apache.hadoop.classification.InterfaceAudience;
022import org.apache.hadoop.classification.InterfaceStability;
023import org.apache.hadoop.metrics2.MetricsRecordBuilder;
024
025/**
026 * The mutable metric interface
027 */
028@InterfaceAudience.Public
029@InterfaceStability.Evolving
030public abstract class MutableMetric {
031  private volatile boolean changed = true;
032
033  /**
034   * Get a snapshot of the metric
035   * @param builder the metrics record builder
036   * @param all if true, snapshot unchanged metrics as well
037   */
038  public abstract void snapshot(MetricsRecordBuilder builder, boolean all);
039
040  /**
041   * Get a snapshot of metric if changed
042   * @param builder the metrics record builder
043   */
044  public void snapshot(MetricsRecordBuilder builder) {
045    snapshot(builder, false);
046  }
047
048  /**
049   * Set the changed flag in mutable operations
050   */
051  protected void setChanged() { changed = true; }
052
053  /**
054   * Clear the changed flag in the snapshot operations
055   */
056  protected void clearChanged() { changed = false; }
057
058  /**
059   * @return  true if metric is changed since last snapshot/snapshot
060   */
061  public boolean changed() { return changed; }
062}