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.mapreduce;
020    
021    import org.apache.hadoop.classification.InterfaceAudience;
022    import org.apache.hadoop.classification.InterfaceStability;
023    import org.apache.hadoop.io.Writable;
024    
025    /**
026     * A named counter that tracks the progress of a map/reduce job.
027     *
028     * <p><code>Counters</code> represent global counters, defined either by the
029     * Map-Reduce framework or applications. Each <code>Counter</code> is named by
030     * an {@link Enum} and has a long for the value.</p>
031     *
032     * <p><code>Counters</code> are bunched into Groups, each comprising of
033     * counters from a particular <code>Enum</code> class.
034     */
035    @InterfaceAudience.Public
036    @InterfaceStability.Stable
037    public interface Counter extends Writable {
038    
039      /**
040       * Set the display name of the counter
041       * @param displayName of the counter
042       * @deprecated (and no-op by default)
043       */
044      @Deprecated
045      void setDisplayName(String displayName);
046    
047      /**
048       * @return the name of the counter
049       */
050      String getName();
051    
052      /**
053       * Get the display name of the counter.
054       * @return the user facing name of the counter
055       */
056      String getDisplayName();
057    
058      /**
059       * What is the current value of this counter?
060       * @return the current value
061       */
062      long getValue();
063    
064      /**
065       * Set this counter by the given value
066       * @param value the value to set
067       */
068      void setValue(long value);
069    
070      /**
071       * Increment this counter by the given value
072       * @param incr the value to increase this counter by
073       */
074      void increment(long incr);
075    }