Package org.apache.hadoop.util

Class JvmPauseMonitor

java.lang.Object

org.apache.hadoop.service.AbstractService

org.apache.hadoop.util.JvmPauseMonitor

All Implemented Interfaces:

java.io.Closeable, java.lang.AutoCloseable, Service

@Private
public class JvmPauseMonitor
extends AbstractService

Class which sets up a simple thread which runs in a loop sleeping for a short interval of time. If the sleep takes significantly longer than its target time, it implies that the JVM or host machine has paused processing, which may cause other problems. If such a pause is detected, the thread logs a message.

Nested Class Summary

Nested classes/interfaces inherited from interface org.apache.hadoop.service.Service

Service.STATE

Constructor Summary

Constructors

Constructor	Description
JvmPauseMonitor()

Method Summary

Modifier and Type	Method	Description
long	getNumGcInfoThresholdExceeded()
long	getNumGcWarnThresholdExceeded()
long	getTotalGcExtraSleepTime()
boolean	isStarted()
static void	main(java.lang.String[] args)	Simple 'main' to facilitate manual testing of the pause monitor.
protected void	serviceInit(Configuration conf)	All initialization code needed by a service.
protected void	serviceStart()	Actions called during the INITED to STARTED transition.
protected void	serviceStop()	Actions called during the transition to the STOPPED state.

Methods inherited from class org.apache.hadoop.service.AbstractService

close, getBlockers, getConfig, getFailureCause, getFailureState, getLifecycleHistory, getName, getServiceState, getStartTime, init, isInState, noteFailure, putBlocker, registerGlobalListener, registerServiceListener, removeBlocker, setConfig, start, stop, toString, unregisterGlobalListener, unregisterServiceListener, waitForServiceToStop

Methods inherited from class java.lang.Object

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

Constructor Detail

JvmPauseMonitor

public JvmPauseMonitor()

Method Detail

serviceInit

protected void serviceInit(Configuration conf)
                    throws java.lang.Exception

Description copied from class: AbstractService

All initialization code needed by a service. This method will only ever be called once during the lifecycle of a specific service instance. Implementations do not need to be synchronized as the logic in AbstractService.init(Configuration) prevents re-entrancy. The base implementation checks to see if the subclass has created a new configuration instance, and if so, updates the base class value

Overrides:

serviceInit in class AbstractService

Parameters:

conf - configuration

Throws:

java.lang.Exception - on a failure -these will be caught, possibly wrapped, and will trigger a service stop

serviceStart

protected void serviceStart()
                     throws java.lang.Exception

Description copied from class: AbstractService

Actions called during the INITED to STARTED transition. This method will only ever be called once during the lifecycle of a specific service instance. Implementations do not need to be synchronized as the logic in AbstractService.start() prevents re-entrancy.

Overrides:

serviceStart in class AbstractService

Throws:

java.lang.Exception - if needed -these will be caught, wrapped, and trigger a service stop

serviceStop

protected void serviceStop()
                    throws java.lang.Exception

Description copied from class: AbstractService

Actions called during the transition to the STOPPED state. This method will only ever be called once during the lifecycle of a specific service instance. Implementations do not need to be synchronized as the logic in AbstractService.stop() prevents re-entrancy. Implementations MUST write this to be robust against failures, including checks for null references -and for the first failure to not stop other attempts to shut down parts of the service.

Overrides:

serviceStop in class AbstractService

Throws:

java.lang.Exception - if needed -these will be caught and logged.

isStarted

public boolean isStarted()

getNumGcWarnThresholdExceeded

public long getNumGcWarnThresholdExceeded()

getNumGcInfoThresholdExceeded

public long getNumGcInfoThresholdExceeded()

getTotalGcExtraSleepTime

public long getTotalGcExtraSleepTime()

main

public static void main(java.lang.String[] args)
                 throws java.lang.Exception

Simple 'main' to facilitate manual testing of the pause monitor. This main function just leaks memory into a list. Running this class with a 1GB heap will very quickly go into "GC hell" and result in log messages about the GC pauses.

Parameters:

args - args.

Throws:

java.lang.Exception - Exception.