org.apache.hadoop.metrics.MetricsUtil Maven / Gradle / Ivy
/**
* 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;
import java.net.InetAddress;
import java.net.UnknownHostException;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
/**
* Utility class to simplify creation and reporting of hadoop metrics.
*
* For examples of usage, see NameNodeMetrics.
* @see org.apache.hadoop.metrics.MetricsRecord
* @see org.apache.hadoop.metrics.MetricsContext
* @see org.apache.hadoop.metrics.ContextFactory
*/
@InterfaceAudience.LimitedPrivate({"HDFS", "MapReduce"})
@InterfaceStability.Evolving
public class MetricsUtil {
public static final Log LOG =
LogFactory.getLog(MetricsUtil.class);
/**
* Don't allow creation of a new instance of Metrics
*/
private MetricsUtil() {}
public static MetricsContext getContext(String contextName) {
return getContext(contextName, contextName);
}
/**
* Utility method to return the named context.
* If the desired context cannot be created for any reason, the exception
* is logged, and a null context is returned.
*/
public static MetricsContext getContext(String refName, String contextName) {
MetricsContext metricsContext;
try {
metricsContext =
ContextFactory.getFactory().getContext(refName, contextName);
if (!metricsContext.isMonitoring()) {
metricsContext.startMonitoring();
}
} catch (Exception ex) {
LOG.error("Unable to create metrics context " + contextName, ex);
metricsContext = ContextFactory.getNullContext(contextName);
}
return metricsContext;
}
/**
* Utility method to create and return new metrics record instance within the
* given context. This record is tagged with the host name.
*
* @param context the context
* @param recordName name of the record
* @return newly created metrics record
*/
public static MetricsRecord createRecord(MetricsContext context,
String recordName)
{
MetricsRecord metricsRecord = context.createRecord(recordName);
metricsRecord.setTag("hostName", getHostName());
return metricsRecord;
}
/**
* Returns the host name. If the host name is unobtainable, logs the
* exception and returns "unknown".
*/
private static String getHostName() {
String hostName = null;
try {
hostName = InetAddress.getLocalHost().getHostName();
}
catch (UnknownHostException ex) {
LOG.info("Unable to obtain hostName", ex);
hostName = "unknown";
}
return hostName;
}
}