org.jboss.mq.server
Class MessageCache

java.lang.Object
  org.jboss.mx.util.JBossNotificationBroadcasterSupport (src) 
      org.jboss.system.ServiceMBeanSupport (src) 
          org.jboss.mq.server.MessageCache

All Implemented Interfaces:

MBeanRegistration (src) , NotificationBroadcaster (src) , NotificationEmitter (src) , java.lang.Runnable, Service (src) , ServiceMBean (src)

public class MessageCache

extends ServiceMBeanSupport (src)

implements MBeanRegistration (src) , java.lang.Runnable

This class implements a Message cache so that larger amounts of messages can be processed without running out of memory. When memory starts getting tight it starts moving messages out of memory and into a file so that they can be recovered later. The locks should be obtained in the following order:
mr, the relevent message we are working with
lruCache, when maintaining the usage order

ONE_MEGABYTE

public static final long ONE_MEGABYTE

See Also:

Constant Field Values (src)

DEFAULT_HIGH_MEMORY_MARK

public static final long DEFAULT_HIGH_MEMORY_MARK

See Also:

Constant Field Values (src)

DEFAULT_MAX_MEMORY_MARK

public static final long DEFAULT_MAX_MEMORY_MARK

See Also:

Constant Field Values (src)

MessageCache

public MessageCache()

getInstance

public MessageCache (src)  getInstance()

The getInstance method

Returns:

a MessageCache value

add

public MessageReference (src)  add(SpyMessage (src)  message,
                            BasicQueue (src)  queue,
                            int stored)
                     throws JMSException (src) 

Adds a message to the cache.

Throws:

JMSException (src)

add

public MessageReference (src)  add(SpyMessage (src)  message,
                            BasicQueue (src)  queue,
                            int stored,
                            DurableSubscriptionID (src)  id)
                     throws JMSException (src) 

Adds a message to the cache.

Throws:

JMSException (src)

addInternal

public MessageReference (src)  addInternal(SpyMessage (src)  message,
                                    BasicQueue (src)  queue,
                                    int stored,
                                    DurableSubscriptionID (src)  id)
                             throws JMSException (src) 

Adds a message to the cache.

Throws:

JMSException (src)

remove

public void remove(MessageReference (src)  mr)
            throws JMSException (src) 

removes a message from the cache

Throws:

JMSException (src)

removeDelayed

public void removeDelayed(MessageReference (src)  mr)
                   throws JMSException (src) 

removes a message from the cache without returning it to the pool used in two phase removes for joint cache/persistence

Throws:

JMSException (src)

removeInternal

protected void removeInternal(MessageReference (src)  mr,
                              boolean clear,
                              boolean reset)
                       throws JMSException (src) 

removes a message from the cache

Throws:

JMSException (src)

run

public void run()

The strategy is that we keep the most recently used messages as Hard references. Then we make the older ones soft references. Making something a soft reference stores it to disk so we need to avoid making soft references if we can avoid it. But once it is made a soft reference does not mean that it is removed from memory. Depending on how agressive the JVM's GC is, it may stay around long enough for it to be used by a client doing a read, saving us read from the file system. If memory gets tight the GC will remove the soft references. What we want to do is make sure there are at least some soft references available so that the GC can reclaim memory.

Specified by:

run in interface java.lang.Runnable

See Also:

Runnable.run()

startService

protected void startService()
                     throws java.lang.Exception

This gets called to start the cache service. Synch. by start

Overrides:

startService in class ServiceMBeanSupport (src)

Throws:

java.lang.Exception

stopService

protected void stopService()

This gets called to stop the cache service.

Overrides:

stopService in class ServiceMBeanSupport (src)

getHardRefCacheSize

public int getHardRefCacheSize()

Gets the hardRefCacheSize

Returns:

Returns a int

getSoftenedSize

public long getSoftenedSize()

The getSoftenedSize method

Returns:

a long value

getSoftRefCacheSize

public int getSoftRefCacheSize()

Gets the softRefCacheSize

Returns:

Returns a int

getTotalCacheSize

public int getTotalCacheSize()

Gets the totalCacheSize

Returns:

Returns a int

getCacheMisses

public long getCacheMisses()

Gets the cacheMisses

Returns:

Returns a int

getCacheHits

public long getCacheHits()

Gets the cacheHits

Returns:

Returns a long

getMakeSoftReferences

public boolean getMakeSoftReferences()

Gets whether to make soft references

Returns:

true when making soft references

setMakeSoftReferences

public void setMakeSoftReferences(boolean makeSoftReferences)

Sets whether to make soft references

getMinimumHard

public int getMinimumHard()

Gets the minimum number of hard messages

Returns:

the minimum number of hard messages

setMinimumHard

public void setMinimumHard(int minimumHard)

Sets the minimum number of hard messages

Parameters:

minimumHard - the minimum number of hard messages

getMaximumHard

public int getMaximumHard()

Gets the maximum number of hard messages

Returns:

the minimum number of hard messages

setMaximumHard

public void setMaximumHard(int maximumHard)

Sets the maximum number of hard messages

Parameters:

maximumHard - the maximum number of hard messages

getSoftenWaitMillis

public long getSoftenWaitMillis()

Gets the length of time to wait before checking whether we should soften

Returns:

the time to wait

setSoftenWaitMillis

public void setSoftenWaitMillis(long millis)

Sets the length of time to wait before checking whether we should soften

Parameters:

millis - the time to wait in millis

getSoftenNoMoreOftenThanMillis

public long getSoftenNoMoreOftenThanMillis()

Gets the minimum length between softening checks

Returns:

the time to wait

setSoftenNoMoreOftenThanMillis

public void setSoftenNoMoreOftenThanMillis(long millis)

Sets the minimum length between softening checks

getSoftenAtLeastEveryMillis

public long getSoftenAtLeastEveryMillis()

Gets the maximum length between softening checks

Returns:

the time

setSoftenAtLeastEveryMillis

public void setSoftenAtLeastEveryMillis(long millis)

Sets the minimum length between softening checks

getHighMemoryMark

public long getHighMemoryMark()

Gets the highMemoryMark

Returns:

Returns a long

setHighMemoryMark

public void setHighMemoryMark(long highMemoryMark)

Sets the highMemoryMark

Parameters:

highMemoryMark - The highMemoryMark to set

getMaxMemoryMark

public long getMaxMemoryMark()

Gets the maxMemoryMark

Returns:

Returns a long

setMaxMemoryMark

public void setMaxMemoryMark(long maxMemoryMark)

Sets the maxMemoryMark

Parameters:

maxMemoryMark - The maxMemoryMark to set

getCurrentMemoryUsage

public long getCurrentMemoryUsage()

Gets the CurrentMemoryUsage

Returns:

Returns a long

getName

public java.lang.String getName()

Description copied from class: ServiceMBeanSupport (src)

Use the short class name as the default for the service name.

Specified by:

getName in interface ServiceMBean (src)

Overrides:

getName in class ServiceMBeanSupport (src)

See Also:

ServiceMBeanSupport.getName()

setCacheStore

public void setCacheStore(ObjectName (src)  cacheStoreName)

See Also:

MessageCacheMBean#setCacheStore(ObjectName)

getCacheStore

public ObjectName (src)  getCacheStore()

The getCacheStore method

Returns:

an ObjectName value