text: /**
   * 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.metrics.util;
  
  import org.apache.hadoop.metrics.MetricsRecord;
  import org.apache.hadoop.util.StringUtils;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  
  /**
   * The MetricsTimeVaryingInt class is for a metric that naturally
   * varies over time (e.g. number of files created). The metrics is accumulated
   * over an interval (set in the metrics config file); the metrics is
   *  published at the end of each interval and then 
   * reset to zero. Hence the counter has the value in the current interval. 
   * 
   * Note if one wants a time associated with the metric then use
   * @see org.apache.hadoop.metrics.util.MetricsTimeVaryingRate
   *
   */
  public class MetricsTimeVaryingInt extends MetricsBase {
  
    private static final Log LOG =
      LogFactory.getLog("org.apache.hadoop.metrics.util");
    
    private int currentValue;
    private int previousIntervalValue;
    
    
    /**
     * Constructor - create a new metric
     * @param nam the name of the metrics to be used to publish the metric
     * @param registry - where the metrics object will be registered
     * @param description - the description
     */
    public MetricsTimeVaryingInt(final String nam,
                                 final MetricsRegistry registry,
                                 final String description) {
      super(nam, description);
      currentValue = 0;
      previousIntervalValue = 0;
      registry.add(nam, this);
    }
    
    /**
     * Constructor - create a new metric
     * @param nam the name of the metrics to be used to publish the metric
     * @param registry - where the metrics object will be registered
     * A description of {@link #NO_DESCRIPTION} is used
     */
    public MetricsTimeVaryingInt(final String nam, final MetricsRegistry registry) {
      this(nam, registry, NO_DESCRIPTION);
    }
    
  
    
    /**
     * Inc metrics for incr vlaue
     * @param incr - number of operations
     */
    public synchronized void inc(final int incr) {
      currentValue += incr;
    }
    
    /**
     * Inc metrics by one
     */
    public synchronized void inc() {
      currentValue++;
    }
  
    private synchronized void intervalHeartBeat() {
       previousIntervalValue = currentValue;
       currentValue = 0;
    }
    
    /**
     * Push the delta  metrics to the mr.
     * The delta is since the last push/interval.
     * 
     * Note this does NOT push to JMX
     * (JMX gets the info via {@link #previousIntervalValue}
     *
     * @param mr
     */
    public synchronized void pushMetric(final MetricsRecord mr) {
      intervalHeartBeat();
      try {
        mr.incrMetric(getName(), getPreviousIntervalValue());
      } catch (Exception e) {
        LOG.info("pushMetric failed for " + getName() + "\n" +
            StringUtils.stringifyException(e));
      }
    }
    
    
    /**
     * The Value at the Previous interval
     * @return prev interval value
     */
    public synchronized int getPreviousIntervalValue() { 
      return previousIntervalValue;
    }
    
    /**
     * The Value at the current interval
     * @return prev interval value
     */
    public synchronized int getCurrentIntervalValue() { 
      return currentValue;
    } 
  }
  