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 */
018package org.apache.hadoop.metrics.spi;
019
020import org.apache.hadoop.classification.InterfaceAudience;
021import org.apache.hadoop.classification.InterfaceStability;
022import org.apache.hadoop.metrics.ContextFactory;
023import org.apache.hadoop.metrics.MetricsServlet;
024
025/** 
026 * A MetricsContext that does not emit data, but, unlike NullContextWithUpdate,
027 * does save it for retrieval with getAllRecords().
028 * 
029 * This is useful if you want to support {@link MetricsServlet}, but
030 * not emit metrics in any other way.
031 */
032@InterfaceAudience.Public
033@InterfaceStability.Evolving
034public class NoEmitMetricsContext extends AbstractMetricsContext {
035    
036    private static final String PERIOD_PROPERTY = "period";
037      
038    /** Creates a new instance of NullContextWithUpdateThread */
039    @InterfaceAudience.Private
040    public NoEmitMetricsContext() {
041    }
042    
043    @Override
044    @InterfaceAudience.Private
045    public void init(String contextName, ContextFactory factory) {
046      super.init(contextName, factory);
047      parseAndSetPeriod(PERIOD_PROPERTY);
048    }
049     
050    /**
051     * Do-nothing version of emitRecord
052     */
053    @Override
054    @InterfaceAudience.Private
055    protected void emitRecord(String contextName, String recordName,
056                              OutputRecord outRec) {
057    }
058}