Package 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

  • Constructor Details

    • AbstractMemoryMonitor

      protected AbstractMemoryMonitor()
      Constructor of this base class.

  • Method Details

    • getLogger

      protected abstract org.apache.logging.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