Package org.apache.hadoop.metrics2

Class MetricsSystem

java.lang.Object

org.apache.hadoop.metrics2.MetricsSystem

All Implemented Interfaces:

MetricsSystemMXBean

Direct Known Subclasses:

MetricsSystemImpl

@Public
@Evolving
public abstract class MetricsSystem
extends Object
implements MetricsSystemMXBean

The metrics system interface. The following components are used for metrics.

• MetricsSource generate and update metrics information.
• MetricsSink consume the metrics information

MetricsSource and MetricsSink register with the metrics system. Implementations of MetricsSystem polls the MetricsSources periodically and pass the MetricsRecords to MetricsSink.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	MetricsSystem.AbstractCallback	Convenient abstract class for implementing callback interface
static interface	MetricsSystem.Callback	The metrics system callback interface (needed for proxies.)

Constructor Summary

Constructors

Constructor	Description
MetricsSystem()

Method Summary

Modifier and Type	Method	Description
abstract MetricsSource	getSource(String name)
abstract MetricsSystem	init(String prefix)
abstract void	publishMetricsNow()	Requests an immediate publish of all metrics from sources to sinks.
abstract <T> T	register(String name, String desc, T source)	Register a metrics source
abstract void	register(MetricsSystem.Callback callback)	Register a callback interface for JMX events
<T> T	register(T source)	Register a metrics source (deriving name and description from the object)
abstract boolean	shutdown()	Shutdown the metrics system completely (usually during server shutdown.)
abstract void	unregisterSource(String name)	Unregister a metrics source

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.apache.hadoop.metrics2.MetricsSystemMXBean

currentConfig, start, startMetricsMBeans, stop, stopMetricsMBeans

Constructor Details

MetricsSystem

public MetricsSystem()

Method Details

init

@Private
public abstract MetricsSystem init(String prefix)

register

public abstract <T> T register(String name,
 String desc,
 T source)

Register a metrics source

Type Parameters:

T - the actual type of the source object

Parameters:

source - object to register

name - of the source. Must be unique or null (then extracted from the annotations of the source object.)

desc - the description of the source (or null. See above.)

Returns:

the source object

Throws:

MetricsException - Metrics Exception.

unregisterSource

public abstract void unregisterSource(String name)

Unregister a metrics source

Parameters:

name - of the source. This is the name you use to call register()

register

public <T> T register(T source)

Register a metrics source (deriving name and description from the object)

Type Parameters:

T - the actual type of the source object

Parameters:

source - object to register

Returns:

the source object

Throws:

MetricsException - Metrics Exception.

getSource

@Private
public abstract MetricsSource getSource(String name)

Parameters:

name - of the metrics source

Returns:

the metrics source (potentially wrapped) object

register

public abstract <T extends MetricsSink> T register(String name,
 String desc,
 T sink)

Register a metrics sink

Type Parameters:

T - the type of the sink

Parameters:

sink - to register

name - of the sink. Must be unique.

desc - the description of the sink

Returns:

the sink

Throws:

MetricsException - Metrics Exception.

register

public abstract void register(MetricsSystem.Callback callback)

Register a callback interface for JMX events

Parameters:

callback - the callback object implementing the MBean interface.

publishMetricsNow

public abstract void publishMetricsNow()

Requests an immediate publish of all metrics from sources to sinks. This is a "soft" request: the expectation is that a best effort will be done to synchronously snapshot the metrics from all the sources and put them in all the sinks (including flushing the sinks) before returning to the caller. If this can't be accomplished in reasonable time it's OK to return to the caller before everything is done.

shutdown

public abstract boolean shutdown()

Shutdown the metrics system completely (usually during server shutdown.) The MetricsSystemMXBean will be unregistered.

Returns:

true if shutdown completed