See: Description
org.apache.hadoop.metrics.spi
org.apache.hadoop.metrics.file
org.apache.hadoop.metrics.ganglia
private ContextFactory contextFactory = ContextFactory.getFactory(); void reportMyMetric(float myMetric) { MetricsContext myContext = contextFactory.getContext("myContext"); MetricsRecord myRecord = myContext.getRecord("myRecord"); myRecord.setMetric("myMetric", myMetric); myRecord.update(); }In this example there are three names:
private MetricsRecord diskStats = contextFactory.getContext("myContext").getRecord("diskStats"); void reportDiskMetrics(String diskName, float diskBusy, float diskUsed) { diskStats.setTag("diskName", diskName); diskStats.setMetric("diskBusy", diskBusy); diskStats.setMetric("diskUsed", diskUsed); diskStats.update(); }
MetricsRecord.update()
is called. Instead it is stored in an
internal table, and the contents of the table are sent periodically.
This can be important for two reasons:
registerUpdater()
method. The benefit of this
versus using java.util.Timer
is that the callbacks will be done
immediately before sending the data, making the data as current as possible.
ContextFactory factory = ContextFactory.getFactory(); ... examine and/or modify factory attributes ... MetricsContext context = factory.getContext("myContext");The factory attributes can be examined and modified using the following
ContextFactory
methods:
Object getAttribute(String attributeName)
String[] getAttributeNames()
void setAttribute(String name, Object value)
void removeAttribute(attributeName)
ContextFactory.getFactory()
initializes the factory attributes by
reading the properties file hadoop-metrics.properties
if it exists
on the class path.
A factory attribute named:
contextName.classshould have as its value the fully qualified name of the class to be instantiated by a call of the
CodeFactory
method
getContext(contextName)
. If this factory attribute is not
specified, the default is to instantiate
org.apache.hadoop.metrics.file.FileContext
.
Other factory attributes are specific to a particular implementation of this
API and are documented elsewhere. For example, configuration attributes for
the file and Ganglia implementations can be found in the javadoc for
their respective packages.Copyright © 2017 Apache Software Foundation. All rights reserved.