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.metrics.spi; 020 021 import org.apache.hadoop.classification.InterfaceAudience; 022 import org.apache.hadoop.classification.InterfaceStability; 023 import org.apache.hadoop.metrics.ContextFactory; 024 025 /** 026 * A null context which has a thread calling 027 * periodically when monitoring is started. This keeps the data sampled 028 * correctly. 029 * In all other respects, this is like the NULL context: No data is emitted. 030 * This is suitable for Monitoring systems like JMX which reads the metrics 031 * when someone reads the data from JMX. 032 * 033 * The default impl of start and stop monitoring: 034 * is the AbstractMetricsContext is good enough. 035 * 036 */ 037 @InterfaceAudience.Public 038 @InterfaceStability.Evolving 039 public class NullContextWithUpdateThread extends AbstractMetricsContext { 040 041 private static final String PERIOD_PROPERTY = "period"; 042 043 /** Creates a new instance of NullContextWithUpdateThread */ 044 @InterfaceAudience.Private 045 public NullContextWithUpdateThread() { 046 } 047 048 @InterfaceAudience.Private 049 public void init(String contextName, ContextFactory factory) { 050 super.init(contextName, factory); 051 parseAndSetPeriod(PERIOD_PROPERTY); 052 } 053 054 055 /** 056 * Do-nothing version of emitRecord 057 */ 058 @InterfaceAudience.Private 059 protected void emitRecord(String contextName, String recordName, 060 OutputRecord outRec) 061 {} 062 063 /** 064 * Do-nothing version of update 065 */ 066 @InterfaceAudience.Private 067 protected void update(MetricsRecordImpl record) { 068 } 069 070 /** 071 * Do-nothing version of remove 072 */ 073 @InterfaceAudience.Private 074 protected void remove(MetricsRecordImpl record) { 075 } 076 }