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
019 package org.apache.hadoop.metrics2.lib;
020
021 import org.apache.hadoop.classification.InterfaceAudience;
022 import org.apache.hadoop.classification.InterfaceStability;
023 import org.apache.hadoop.metrics2.MetricsRecordBuilder;
024
025 /**
026 * The mutable metric interface
027 */
028 @InterfaceAudience.Public
029 @InterfaceStability.Evolving
030 public 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 }