branch-2.0.4-alpha/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/metrics2/lib/MutableGauge.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.metrics2.lib;

import static com.google.common.base.Preconditions.*;

import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.metrics2.MetricsInfo;

/**
 * The mutable gauge metric interface
 */
@InterfaceAudience.Public
@InterfaceStability.Evolving
public abstract class MutableGauge extends MutableMetric {
  private final MetricsInfo info;

  protected MutableGauge(MetricsInfo info) {
    this.info = checkNotNull(info, "metric info");
  }

  protected MetricsInfo info() {
    return info;
  }

  /**
   * Increment the value of the metric by 1
   */
  public abstract void incr();

  /**
   * Decrement the value of the metric by 1
   */
  public abstract void decr();
}