org.apache.hadoop.metrics2.lib

Class MutableRollingAverages

java.lang.Object

org.apache.hadoop.metrics2.lib.MutableMetric

org.apache.hadoop.metrics2.lib.MutableRollingAverages

All Implemented Interfaces:

Closeable, AutoCloseable

@InterfaceAudience.Public
 @InterfaceStability.Evolving
public class MutableRollingAverages
extends MutableMetric
implements Closeable

This class maintains a group of rolling average metrics. It implements the algorithm of rolling average, i.e. a number of sliding windows are kept to roll over and evict old subsets of samples. Each window has a subset of samples in a stream, where sub-sum and sub-total are collected. All sub-sums and sub-totals in all windows will be aggregated to final-sum and final-total used to compute final average, which is called rolling average.

Constructor Summary

Constructors

Constructor and Description
MutableRollingAverages(String metricValueName) Constructor for MutableRollingAverages.

Method Summary

Modifier and Type	Method and Description
void	add(String name, long value)
void	close()
void	collectThreadLocalStates() Collects states maintained in ThreadLocal, if any.
Map<String,Double>	getStats(long minSamples) Retrieve a map of metric name -> (aggregate).
void	snapshot(MetricsRecordBuilder builder, boolean all) Get a snapshot of the metric

Methods inherited from class org.apache.hadoop.metrics2.lib.MutableMetric

changed, clearChanged, setChanged, snapshot

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

MutableRollingAverages

public MutableRollingAverages(String metricValueName)

Constructor for MutableRollingAverages.

Parameters:

metricValueName -

Method Detail

snapshot

public void snapshot(MetricsRecordBuilder builder,
                     boolean all)

Description copied from class: MutableMetric

Get a snapshot of the metric

Specified by:

snapshot in class MutableMetric

Parameters:

builder - the metrics record builder

all - if true, snapshot unchanged metrics as well

collectThreadLocalStates

public void collectThreadLocalStates()

Collects states maintained in ThreadLocal, if any.

add

public void add(String name,
                long value)

Parameters:

name - name of metric

value - value of metric

close

public void close()
           throws IOException

Specified by:

close in interface Closeable

Specified by:

close in interface AutoCloseable

Throws:

IOException

getStats

public Map<String,Double> getStats(long minSamples)

Retrieve a map of metric name -> (aggregate). Filter out entries that don't have at least minSamples.

Returns:

a map of peer DataNode Id to the average latency to that node seen over the measurement period.