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 package org.apache.hadoop.metrics.spi;
019
020 import org.apache.hadoop.classification.InterfaceAudience;
021 import org.apache.hadoop.classification.InterfaceStability;
022 import org.apache.hadoop.metrics.ContextFactory;
023 import 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
034 public 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 @InterfaceAudience.Private
044 public void init(String contextName, ContextFactory factory) {
045 super.init(contextName, factory);
046 parseAndSetPeriod(PERIOD_PROPERTY);
047 }
048
049 /**
050 * Do-nothing version of emitRecord
051 */
052 @InterfaceAudience.Private
053 protected void emitRecord(String contextName, String recordName,
054 OutputRecord outRec) {
055 }
056 }