mondrian.util
Class AbstractMemoryMonitor

java.lang.Object
  mondrian.util.AbstractMemoryMonitor

All Implemented Interfaces:

MemoryMonitor, MemoryMonitor.Test

Direct Known Subclasses:

NotificationMemoryMonitor

public abstract class AbstractMemoryMonitor
extends Object
implements MemoryMonitor, MemoryMonitor.Test

Abstract implementation of MemoryMonitor. Base class for different memory monitoring strategies.

Since:

Feb 03 2007

Author:

Richard M. Emberson

Nested Class Summary

(package private) static class

AbstractMemoryMonitor.Entry Class used to associate Listener and threshold.

Nested classes/interfaces inherited from interface mondrian.util.MemoryMonitor

MemoryMonitor.Listener, MemoryMonitor.Test

Constructor Summary

protected

AbstractMemoryMonitor() Constructor of this base class.

Method Summary

boolean	addListener(MemoryMonitor.Listener listener) Adds a Listener using the default threshold percentage.
boolean	addListener(MemoryMonitor.Listener listener, int percentage) Adds a Listener to the MemoryMonitor with a given threshold percentage.
protected long	convertPercentageToThreshold(int percentage) Converts a percentage threshold to its corresponding memory value, (percentage * maximum-memory / 100).
protected int	convertThresholdToPercentage(long threshold) Converts a memory value to its percentage.
protected long	generateLowThreshold() Returns the lowest threshold from the list of Listeners.
int	getDefaultThresholdPercentage() Returns the default memory notification percentage.
protected abstract org.apache.log4j.Logger	getLogger() Returns the Logger.
protected long	getLowThreshold() Returns the current lowest threshold of all registered Listeners.
protected void	notifyListeners(long usedMemory, long maxMemory) Notifies all Listeners that memory is running short.
protected void	notifyNewLowThreshold(long newLowThreshold) Derived classes implement this method if they wish to be notified when there is a new lowest threshold.
void	removeAllListener() Clear out all Listeners and turnoff JVM memory notification.
boolean	removeListener(MemoryMonitor.Listener listener) Removes a Listener from the MemoryMonitor.
void	resetFromTest() This should only be called when one is switching from a test MemoryMonitor back to the default system MemoryMonitor.
void	updateListenerThreshold(MemoryMonitor.Listener listener, int percentage) Changes the threshold percentage of a given Listener.
protected int	usagePercentage() Returns how much memory is currently being used as a percentage.

Methods inherited from class java.lang.Object

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

Methods inherited from interface mondrian.util.MemoryMonitor

getMaxMemory, getUsedMemory

Constructor Detail

AbstractMemoryMonitor

protected AbstractMemoryMonitor()

Constructor of this base class.

Method Detail

getLogger

protected abstract org.apache.log4j.Logger getLogger()

Returns the Logger.

Returns:

the Logger.

getLowThreshold

protected long getLowThreshold()

Returns the current lowest threshold of all registered Listeners.

Returns:

the lowest threshold.

getDefaultThresholdPercentage

public int getDefaultThresholdPercentage()

Returns the default memory notification percentage.

This is the value of the Mondrian MondrianProperties.MemoryMonitorThreshold property.

Returns:

the default threshold percentage.

addListener

public boolean addListener(MemoryMonitor.Listener listener)

Description copied from interface: MemoryMonitor

Adds a Listener using the default threshold percentage.

If the threshold is below the Java5 memory managment system's threshold, then the Listener is notified from within this method.

Specified by:

addListener in interface MemoryMonitor

Parameters:

listener - the Listener to be added.

Returns:

true if the Listener was added and false otherwise.

addListener

public boolean addListener(MemoryMonitor.Listener listener,
                           int percentage)

Description copied from interface: MemoryMonitor

Adds a Listener to the MemoryMonitor with a given threshold percentage.

If the threshold is below the Java5 memory managment system's threshold, then the Listener is notified from within this method.

Specified by:

addListener in interface MemoryMonitor

Parameters:

listener - the Listener to be added.

percentage - the threshold percentage for this Listener.

Returns:

true if the Listener was added and false otherwise.

updateListenerThreshold

public void updateListenerThreshold(MemoryMonitor.Listener listener,
                                    int percentage)

Description copied from interface: MemoryMonitor

Changes the threshold percentage of a given Listener.

If the new value is below the system's current value, then the Listener will have its notification callback called while in this method - so a client should always check if its notification method was called immediately after calling this method.

This method can be used if, for example, an algorithm has different approaches that result in different memory usage profiles; one, large memory but fast and a second which is low-memory but slow. The algorithm starts with the large memory approach, receives a low memory notification, switches to the low memory approach and changes when it should be notified for this new approach. The first approach need to be notified at a lower percentage because it uses lots of memory, possibly quickly; while the second approach, possibly a file based algorithm, has smaller memory requirements and uses memory less quickly thus one can live with a higher notification threshold percentage.

Specified by:

updateListenerThreshold in interface MemoryMonitor

Parameters:

listener - the Listener being updated.

percentage - new percentage threshold.

removeListener

public boolean removeListener(MemoryMonitor.Listener listener)

Description copied from interface: MemoryMonitor

Removes a Listener from the MemoryMonitor. Returns true if listener was removed and false otherwise.

Specified by:

removeListener in interface MemoryMonitor

Parameters:

listener - the listener to be removed

Returns:

true if listener was removed.

removeAllListener

public void removeAllListener()

Description copied from interface: MemoryMonitor

Clear out all Listeners and turnoff JVM memory notification.

Specified by:

removeAllListener in interface MemoryMonitor

generateLowThreshold

protected long generateLowThreshold()

Returns the lowest threshold from the list of Listeners. If there are no Listeners, then return the maximum memory usage. Returns Long.MAX_VALUE if there are no Listeners

Returns:

the lowest threshold or Long.MAX_VALUE

notifyListeners

protected void notifyListeners(long usedMemory,
                               long maxMemory)

Notifies all Listeners that memory is running short.

Parameters:

usedMemory - the current memory used.

maxMemory - the maximum memory.

notifyNewLowThreshold

protected void notifyNewLowThreshold(long newLowThreshold)

Derived classes implement this method if they wish to be notified when there is a new lowest threshold.

Parameters:

newLowThreshold - the new low threshold.

convertPercentageToThreshold

protected long convertPercentageToThreshold(int percentage)

Converts a percentage threshold to its corresponding memory value, (percentage * maximum-memory / 100).

Parameters:

percentage - the threshold.

Returns:

the memory value.

convertThresholdToPercentage

protected int convertThresholdToPercentage(long threshold)

Converts a memory value to its percentage.

Parameters:

threshold - the memory value.

Returns:

the percentage.

usagePercentage

protected int usagePercentage()

Returns how much memory is currently being used as a percentage.

Returns:

currently used memory as a percentage.

resetFromTest

public void resetFromTest()

Description copied from interface: MemoryMonitor.Test

This should only be called when one is switching from a test MemoryMonitor back to the default system MemoryMonitor. In particular, look at the MemoryMonitorFactory's clearThreadLocalClassName() method for its usage.

Specified by:

resetFromTest in interface MemoryMonitor.Test