common/src/java/org/apache/hadoop/metrics/spi/NoEmitMetricsContext.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.metrics.spi;

import org.apache.hadoop.metrics.ContextFactory;
import org.apache.hadoop.metrics.MetricsServlet;

/** 
 * A MetricsContext that does not emit data, but, unlike NullContextWithUpdate,
 * does save it for retrieval with getAllRecords().
 * 
 * This is useful if you want to support {@link MetricsServlet}, but
 * not emit metrics in any other way.
 */
public class NoEmitMetricsContext extends AbstractMetricsContext {
    
    private static final String PERIOD_PROPERTY = "period";
      
    /** Creates a new instance of NullContextWithUpdateThread */
    public NoEmitMetricsContext() {
    }
    
    public void init(String contextName, ContextFactory factory) {
      super.init(contextName, factory);
      parseAndSetPeriod(PERIOD_PROPERTY);
    }
     
    /**
     * Do-nothing version of emitRecord
     */
    protected void emitRecord(String contextName, String recordName,
                              OutputRecord outRec) {
    }
}