com.tangosol.net.cache
Class OverflowMap

java.lang.Object
  com.tangosol.util.Base
      com.tangosol.util.AbstractKeyBasedMap
          com.tangosol.util.AbstractKeySetBasedMap
              com.tangosol.net.cache.OverflowMap

All Implemented Interfaces:

CacheMap, ObservableMap, Map

public class OverflowMap
extends AbstractKeySetBasedMap
implements CacheMap

An Observable Map implementation that wraps two maps - a front map (assumed to be fast but limited in its maximum size) and a back map (assumed to be slower but much less limited in its maximum size).

The OverflowMap is observable, and as such it is allowed to be an active data structure. In other words, it supports item expiration, eviction, and other types of "self-generating" events. (The SimpleOverflowMap) is an alternative that may be more efficient if the overflow map is passive.) As a consequence of the requirements for managing the overflow map as an active data structure, the OverflowMap maintains information about each entry in the map; in practice, this will limit the size of the OverflowMap since all keys and some additional information for each key will be maintained in memory. On the other hand, by maintaining this information in memory, certain operations will be more efficient, such as the methods containsKey(), size(), keySet().iterator(), etc. (Again, for an alternative, see SimpleOverflowMap, which does not maintain the entire set of keys in memory.)

The primary reason why OverflowMap is based on the AbstractKeySetBasedMap is that the set of keys within the OverflowMap is considered to be "known", although not altogether stable due to concurrency issues (the OverflowMap is designed to support a high level of concurrency). AbstractKeySetBasedMap conceptually delegates many operations down to its key Set, which the OverflowMap implementation reverses (by having the implementations on the OverflowMap itself). However, the key and entry Sets and the values Collection benefit significantly in terms of their ability to optimize the Collection.iterator() and Collection.toArray() methods.

Further, as a result (and sometimes as a consequence) of its observability, the OverflowMap supports (and has to support) a number of capabilities that the SimpleOverflowMap does not:

• Expiry - the entries in the OverflowMap can each have their own expiry, which is respected regardless of whether the entry is being managed in the front and/or back map.
• Reentrancy - since an event listener on the OverflowMap can respond to an event in an unpredictable manner, including by attempting to undo or compensate for or react to the event, the OverflowMap is forced to support reentrancy.

Since:

Coherence 2.2

Author:

cp 2003.05.24, cp 2005.08.11 re-architected and split out SimpleOverflowMap

Nested Class Summary

protected class	OverflowMap.BackMapListener A listener for the back map.
class	OverflowMap.EntrySet A set of entries backed by this map.
protected static class	OverflowMap.ExpirableStatus The ExpirableStatus adds expiry to the base Status object.
protected class	OverflowMap.FrontMapListener A listener for the front map that moves evictions to the back map.
protected static class	OverflowMap.HistoricCacheEvent A CacheEvent that carries a recent value (to avoid it being lost during eviction).
protected class	OverflowMap.InternalKeySet A read-only set of keys backed by this map.
protected static class	OverflowMap.Status The Status object is used to manage concurrency at the key level for the key-level operations against the Map, to track all the items in the front Map, to manage the state transition for operations occurring against the Map, and to coordinate events across multiple threads.

Nested classes/interfaces inherited from class com.tangosol.util.AbstractKeySetBasedMap

AbstractKeySetBasedMap.KeyIterator, AbstractKeySetBasedMap.KeySet, AbstractKeySetBasedMap.ValuesCollection

Nested classes/interfaces inherited from interface java.util.Map

Map.Entry

Field Summary

static int	ENTRY_DELETED This event indicates that an entry has been removed from the map.
static int	ENTRY_INSERTED This event indicates that an entry has been added to the map.
static int	ENTRY_UPDATED This event indicates that an entry has been updated in the map.

Fields inherited from interface com.tangosol.net.cache.CacheMap

EXPIRY_DEFAULT, EXPIRY_NEVER

Constructor Summary

OverflowMap(ObservableMap mapFront, Map mapBack)
Construct a OverflowMap using two specified maps: FrontMap (aka "cache" or "shallow") and BackMap (aka "file" or "deep") If the BackMap implements the ObservableMap interface a listener will be added to the BackMap to invalidate items updated [externally] in the back map.

Method Summary

void	addMapListener(MapListener listener) Add a standard map listener that will receive all events (inserts, updates, deletes) that occur against the map, with the key, old-value and new-value included.
void	addMapListener(MapListener listener, Filter filter, boolean fLite) Add a map listener that receives events based on a filter evaluation.
void	addMapListener(MapListener listener, Object oKey, boolean fLite) Add a map listener for a specific key.
protected void	adjustSize(int cItems) Adjust the number of entries in the OverflowMap.
protected OverflowMap.Status	beginKeyProcess(Object oKey) Block until a key is available for processing, and return the Status object for that key.
protected void	beginMapProcess() Block until this thread has exclusive access to perform operations against the OverflowMap.
void	clear() Clear all key/value mappings.
protected void	closeStatus(OverflowMap.Status status) Helper method to close a Status, processing any pending events as part of the process.
boolean	containsKey(Object oKey) Returns true if this map contains a mapping for the specified key.
protected void	dispatchEvent(OverflowMap.Status status, int nId, Object oKey, Object oValueOld, Object oValueNew, boolean fSynthetic) Dispatch an event containing the passed event information.
protected void	dispatchEvent(OverflowMap.Status status, MapEvent evt) Dispatch the passed event.
protected void	endKeyProcess(Object oKey, OverflowMap.Status status) Finish the processing of a single key.
protected void	endMapProcess() Release exclusive access for the OverflowMap.
void	evict() Flush items that have expired.
protected static void	evict(Map map) If the passed Map supports it, evict its expired data.
Object	get(Object oKey) Returns the value to which this map maps the specified key.
Map	getAll(Collection colKeys) Get all the specified keys, if they are in the Map.
Map	getBackMap() Returns the back Map.
protected MapListener	getBackMapListener() Get the MapListener for the back map.
CacheStatistics	getCacheStatistics() Returns the CacheStatistics for this cache.
protected List	getDeferredList() Obtain the List of keys that may have deferred events.
protected LongArray	getExpiryArray() Obtain the array of keys that have an expiration, indexed by expiration times.
int	getExpiryDelay() Determine the "time to live" for each individual cache entry.
ObservableMap	getFrontMap() Returns the front Map.
protected MapListener	getFrontMapListener() Get the MapListener for the front map.
protected Object	getInternal(Object oKey, boolean fStats, Map mapResult) A combined implementation of get(java.lang.Object) and getAll(java.util.Collection) that eliminates duplicate (and very complex) code.
protected Set	getInternalKeySet() Obtain a set of keys that are represented by this Map.
protected static Object	getLatestOldValue(MapEvent evt) Obtain the latest old value from the passed event.
protected MapListenerSupport	getMapListenerSupport() Accessor for the MapListenerSupport for sub-classes.
protected int	getSize() Obtain the number of entries in the OverflowMap.
protected Map	getStatusMap() Obtain the Map of Status objects for entries managed by this Overflow Map.
protected ThreadGate	getThreadGate() Obtain the ThreadGate for managing key-level and Collection-level operations against the Map, versus Map-level operations themselves.
protected boolean	hasListeners() Determine if the OverflowMap has any listeners at all.
protected MapListener	instantiateBackMapListener() Factory pattern: Back Map Listener.
protected Set	instantiateEntrySet() Factory pattern: Create a Set that represents the entries in the Map.
protected MapListener	instantiateFrontMapListener() Factory pattern: Front Map Listener.
protected Set	instantiateInternalKeySet() Factory pattern: Create a read-only Set of keys in the Overflow Map
protected OverflowMap.Status	instantiateStatus() Factory method: Instantiate a Status object.
boolean	isEmpty() Returns true if this map contains no key-value mappings.
boolean	isExpiryEnabled() Determine if this OverflowMap supports entry expiry.
boolean	isFrontPutBlind() Determine if the front Map is more efficiently updated using putAll.
protected boolean	isInternalKeySetIteratorMutable() Determine if this Iterator should remove an iterated item by calling remove on the internal key Set Iterator, or by calling removeBlind on the map itself.
boolean	isNullValuesAllowed() Determine if null values are permitted.
protected static boolean	isSynthetic(MapEvent evt) Helper method to determine if an event is synthetic.
protected static MapEvent	mergeEvents(MapEvent evtOld, MapEvent evtNew) Merge two events that have been raised in sequence from a given map.
protected void	onBackEvent(MapEvent evtBack) Handle an event occuring against the "back" map.
protected void	onFrontEvent(MapEvent evt) Either handle an event by turning it over to another thread that is processing the key specified by the event, or take responsibility on this thread for deferring the event and registering its immediate side-effects.
protected boolean	prepareStatus(Object oKey, OverflowMap.Status status) Validate the status and process any deferred events or pending expiry.
protected void	processBackEvent(OverflowMap.Status status, MapEvent evtBack) Process an event.
protected void	processDeferredEvents(boolean fProcessAll) Process deferred events, if there are any.
protected void	processEvent(OverflowMap.Status status, MapEvent evt) Process an arbitrary event that has occurred against either the front or back map.
protected void	processFrontEvent(OverflowMap.Status status, MapEvent evtFront) Process an event.
Object	put(Object oKey, Object oValue) Associates the specified value with the specified key in this map.
Object	put(Object oKey, Object oValue, long cMillis) Associates the specified value with the specified key in this cache.
void	putAll(Map map) Copies all of the mappings from the specified map to this map.
protected Object	putInternal(Object oKey, Object oValue, boolean fStoreOnly, long cMillis) A combined implementation of put(Object, Object) and "void put(Object, Object)" that eliminates duplicate (and muchos complex) code between the put(java.lang.Object, java.lang.Object) and putAll(java.util.Map) methods.
protected static void	putOne(Map map, Object oKey, Object oValue, boolean fPutBlind) Helper to put a value into a map using either the put or putAll method.
protected void	registerExpiry(Object oKey, long ldtExpire) Register an expiry for the specified key.
protected void	releaseClosedStatus(Object oKey) Helper method to encapsulate the release of a Status object on which closeProcessing() has already been called.
Object	remove(Object oKey) Removes the mapping for this key from this map if present.
protected boolean	removeBlind(Object oKey) Removes the mapping for this key from this map if present.
protected Object	removeInternal(Object oKey, boolean fCheckRemovedOnly, boolean fEviction) A combined implementation of remove() and removeBlind() that eliminates duplicate (and muchos complex) code
void	removeMapListener(MapListener listener) Remove a standard map listener that previously signed up for all events.
void	removeMapListener(MapListener listener, Filter filter) Remove a map listener that previously signed up for events based on a filter evaluation.
void	removeMapListener(MapListener listener, Object oKey) Remove a map listener that previously signed up for events about a specific key.
protected void	setBackMapListener(MapListener listener) Specify the MapListener for the back map.
protected void	setExpiryArray(LongArray laExpiry) Specify the array of keys that have an expiration, indexed by expiration times.
void	setExpiryDelay(int cMillis) Specify the "time to live" for cache entries.
void	setExpiryEnabled(boolean fEnableExpiry) Specify whether or not entry expiry is supported.
protected void	setFrontMapListener(MapListener listener) Specify the MapListener for the front map.
void	setFrontPutBlind(boolean fUseFrontPutAll) Specify whether the front Map is more efficiently updated using putAll.
void	setNullValuesAllowed(boolean fAllowNulls) Specify whether null values are permitted.
protected void	setSize(int cItems) Update the number of entries in the OverflowMap.
int	size() Returns the number of key-value mappings in this map.
protected void	unregisterExpiry(Object oKey, long ldtExpire) Unregister the specified key expiry that is registered to expire at the specified time.
protected static void	verifyNoNulls(Collection collection, String sAssert) Check the passed collection for nulls, and fail if it contains any.
protected static void	warnEventSequence(MapEvent evtOld, MapEvent evtNew) Issue a one-time warning that events are being received in an order than cannot be explained by normal operation according to the contracts expected by this OverflowMap.
protected void	warnMissingEvent(Object oKey, int nId, boolean fFront) An expected event did not get raised.
protected void	warnUnfathomable(MapEvent evt) Something totally inexplicable has occurred.

Methods inherited from class com.tangosol.util.AbstractKeySetBasedMap

instantiateKeyIterator, instantiateKeySet, instantiateValues, iterateKeys

Methods inherited from class com.tangosol.util.AbstractKeyBasedMap

clone, containsValue, entrySet, equals, hashCode, keySet, toString, values

Methods inherited from interface java.util.Map

containsValue, entrySet, equals, hashCode, keySet, values

Field Detail

ENTRY_INSERTED

public static final int ENTRY_INSERTED

This event indicates that an entry has been added to the map.

See Also:

Constant Field Values

ENTRY_UPDATED

public static final int ENTRY_UPDATED

This event indicates that an entry has been updated in the map.

See Also:

Constant Field Values

ENTRY_DELETED

public static final int ENTRY_DELETED

This event indicates that an entry has been removed from the map.

See Also:

Constant Field Values

Constructor Detail

OverflowMap

public OverflowMap(ObservableMap mapFront,
                   Map mapBack)

Construct a OverflowMap using two specified maps:

• FrontMap (aka "cache" or "shallow") and
• BackMap (aka "file" or "deep")

If the BackMap implements the ObservableMap interface a listener will be added to the BackMap to invalidate items updated [externally] in the back map.

Parameters:

mapBack - back map

mapFront - front map

Method Detail

clear

public void clear()

Clear all key/value mappings.

Specified by:

clear in interface Map

Overrides:

clear in class AbstractKeyBasedMap

containsKey

public boolean containsKey(Object oKey)

Returns true if this map contains a mapping for the specified key.

Specified by:

containsKey in interface Map

Overrides:

containsKey in class AbstractKeySetBasedMap

Returns:

true if this map contains a mapping for the specified key, false otherwise.

get

public Object get(Object oKey)

Returns the value to which this map maps the specified key.

Specified by:

get in interface Map

Specified by:

get in class AbstractKeyBasedMap

Parameters:

oKey - the key object

Returns:

the value to which this map maps the specified key, or null if the map contains no mapping for this key

isEmpty

public boolean isEmpty()

Returns true if this map contains no key-value mappings.

Specified by:

isEmpty in interface Map

Overrides:

isEmpty in class AbstractKeySetBasedMap

Returns:

true if this map contains no key-value mappings

put

public Object put(Object oKey,
                  Object oValue)

Associates the specified value with the specified key in this map.

Specified by:

put in interface CacheMap

Specified by:

put in interface Map

Overrides:

put in class AbstractKeyBasedMap

Parameters:

oKey - key with which the specified value is to be associated

oValue - value to be associated with the specified key

Returns:

previous value associated with specified key, or null if there was no mapping for key

putAll

public void putAll(Map map)

Copies all of the mappings from the specified map to this map. The effect of this call is equivalent to that of calling AbstractKeyBasedMap.put(java.lang.Object, java.lang.Object) on this map once for each mapping in the passed map. The behavior of this operation is unspecified if the passed map is modified while the operation is in progress.

Specified by:

putAll in interface Map

Overrides:

putAll in class AbstractKeyBasedMap

Parameters:

map - the Map containing the key/value pairings to put into this Map

remove

public Object remove(Object oKey)

Removes the mapping for this key from this map if present. Expensive: updates both the underlying cache and the local cache.

Specified by:

remove in interface Map

Overrides:

remove in class AbstractKeyBasedMap

Parameters:

oKey - key whose mapping is to be removed from the map

Returns:

previous value associated with specified key, or null if there was no mapping for key. A null return can also indicate that the map previously associated null with the specified key, if the implementation supports null values.

size

public int size()

Returns the number of key-value mappings in this map.

Specified by:

size in interface Map

Overrides:

size in class AbstractKeySetBasedMap

Returns:

the number of key-value mappings in this map

put

public Object put(Object oKey,
                  Object oValue,
                  long cMillis)

Associates the specified value with the specified key in this cache. If the cache previously contained a mapping for this key, the old value is replaced. This variation of the CacheMap.put(Object oKey, Object oValue) method allows the caller to specify an expiry (or "time to live") for the cache entry.

Specified by:

put in interface CacheMap

Parameters:

oKey - key with which the specified value is to be associated

oValue - value to be associated with the specified key

cMillis - the number of milliseconds until the cache entry will expire, also referred to as the entry's "time to live"; pass CacheMap.EXPIRY_DEFAULT to use the cache's default time-to-live setting; pass CacheMap.EXPIRY_NEVER to indicate that the cache entry should never expire; this milliseconds value is not a date/time value, such as is returned from System.currentTimeMillis()

Returns:

previous value associated with specified key, or null if there was no mapping for key. A null return can also indicate that the map previously associated null with the specified key, if the implementation supports null values

getAll

public Map getAll(Collection colKeys)

Get all the specified keys, if they are in the Map. For each key that is in the cache, that key and its corresponding value will be placed in the map that is returned by this method. The absence of a key in the returned map indicates that it was not in the cache, which may imply (for caches that can load behind the scenes) that the requested data could not be loaded.

Specified by:

getAll in interface CacheMap

Overrides:

getAll in class AbstractKeyBasedMap

Parameters:

colKeys - a collection of keys that may be in the named cache

Returns:

a Map of keys to values for the specified keys passed in colKeys

addMapListener

public void addMapListener(MapListener listener)

Add a standard map listener that will receive all events (inserts, updates, deletes) that occur against the map, with the key, old-value and new-value included. This has the same result as the following call:

   addMapListener(listener, (Filter) null, false);
 

Specified by:

addMapListener in interface ObservableMap

Parameters:

listener - the MapEvent listener to add

removeMapListener

public void removeMapListener(MapListener listener)

Remove a standard map listener that previously signed up for all events. This has the same result as the following call:

   removeMapListener(listener, (Filter) null);
 

Specified by:

removeMapListener in interface ObservableMap

Parameters:

listener - the listener to remove

addMapListener

public void addMapListener(MapListener listener,
                           Object oKey,
                           boolean fLite)

Add a map listener for a specific key.

The listeners will receive MapEvent objects, but if fLite is passed as true, they might not contain the OldValue and NewValue properties.

To unregister the MapListener, use the ObservableMap.removeMapListener(MapListener, Object) method.

Specified by:

addMapListener in interface ObservableMap

Parameters:

listener - the MapEvent listener to add

oKey - the key that identifies the entry for which to raise events

fLite - true to indicate that the MapEvent objects do not have to include the OldValue and NewValue property values in order to allow optimizations

removeMapListener

public void removeMapListener(MapListener listener,
                              Object oKey)

Remove a map listener that previously signed up for events about a specific key.

Specified by:

removeMapListener in interface ObservableMap

Parameters:

listener - the listener to remove

oKey - the key that identifies the entry for which to raise events

addMapListener

public void addMapListener(MapListener listener,
                           Filter filter,
                           boolean fLite)

Add a map listener that receives events based on a filter evaluation.

The listeners will receive MapEvent objects, but if fLite is passed as true, they might not contain the OldValue and NewValue properties.

To unregister the MapListener, use the ObservableMap.removeMapListener(MapListener, Filter) method.

Specified by:

addMapListener in interface ObservableMap

Parameters:

listener - the MapEvent listener to add

filter - a filter that will be passed MapEvent objects to select from; a MapEvent will be delivered to the listener only if the filter evaluates to true for that MapEvent (see MapEventFilter); null is equivalent to a filter that alway returns true

fLite - true to indicate that the MapEvent objects do not have to include the OldValue and NewValue property values in order to allow optimizations

removeMapListener

public void removeMapListener(MapListener listener,
                              Filter filter)

Remove a map listener that previously signed up for events based on a filter evaluation.

Specified by:

removeMapListener in interface ObservableMap

Parameters:

listener - the listener to remove

filter - the filter that was passed into the corresponding addMapListener() call

removeBlind

protected boolean removeBlind(Object oKey)

Removes the mapping for this key from this map if present. This method exists to allow sub-classes to optmiize remove functionalitly for situations in which the original value is not required.

Overrides:

removeBlind in class AbstractKeyBasedMap

Parameters:

oKey - key whose mapping is to be removed from the map

Returns:

true iff the Map changed as the result of this operation

getInternalKeySet

protected Set getInternalKeySet()

Obtain a set of keys that are represented by this Map.

The AbstractKeySetBasedMap only utilizes the internal key set as a read-only resource.

Specified by:

getInternalKeySet in class AbstractKeySetBasedMap

Returns:

an internal Set of keys that are contained by this Map

isInternalKeySetIteratorMutable

protected boolean isInternalKeySetIteratorMutable()

Determine if this Iterator should remove an iterated item by calling remove on the internal key Set Iterator, or by calling removeBlind on the map itself.

Overrides:

isInternalKeySetIteratorMutable in class AbstractKeySetBasedMap

Returns:

true to remove using the internal key Set Iterator or false to use the AbstractKeyBasedMap.removeBlind(Object) method

getInternal

protected Object getInternal(Object oKey,
                             boolean fStats,
                             Map mapResult)

A combined implementation of get(java.lang.Object) and getAll(java.util.Collection) that eliminates duplicate (and very complex) code.

Parameters:

oKey - the key to access

fStats - pass true to update statistics

mapResult - pass a map into which the key and its value will be put iff the key is contained within the overflow map

Returns:

the value (which may be null) is returned from the entry if it exists, otherwise null is returned

putInternal

protected Object putInternal(Object oKey,
                             Object oValue,
                             boolean fStoreOnly,
                             long cMillis)

A combined implementation of put(Object, Object) and "void put(Object, Object)" that eliminates duplicate (and muchos complex) code between the put(java.lang.Object, java.lang.Object) and putAll(java.util.Map) methods. Additionally implements the put-with-expiry option.

Parameters:

oKey - the key to store

oValue - the value to store

fStoreOnly - pass true to simply store the new value, or false to both store the new value and return the previous value

cMillis - the time-to-live for the entry as defined by CacheMap.put(Object, Object, long)

Returns:

the previous value if fStoreOnly is false and the entry existed in the overflow map, otherwise undefined

removeInternal

protected Object removeInternal(Object oKey,
                                boolean fCheckRemovedOnly,
                                boolean fEviction)

A combined implementation of remove() and removeBlind() that eliminates duplicate (and muchos complex) code

Parameters:

oKey - the key to remove

fCheckRemovedOnly - pass true to only check for entry existence

fEviction - pass true if the removal is an eviction and if the status is already owned by this thread

Returns:

if only checking for existence, then a Boolean value is returned, otherwise the value (which may be null) is returned from the entry if it exists, otherwise null is returned

getFrontMap

public ObservableMap getFrontMap()

Returns the front Map.

Warning: Direct modifications of the returned map may cause unpredictable behavior of the Overflow Map.

Returns:

the front Map

getBackMap

public Map getBackMap()

Returns the back Map.

Warning: Direct modifications of the returned map may cause unpredictable behavior of the Overflow Map.

Returns:

the back Map

getExpiryDelay

public int getExpiryDelay()

Determine the "time to live" for each individual cache entry.

Returns:

the number of milliseconds that a cache entry value will live, or EXPIRY_NEVER if the entries never expire by default

setExpiryDelay

public void setExpiryDelay(int cMillis)

Specify the "time to live" for cache entries. This does not affect the already-scheduled expiry of existing entries.

Parameters:

cMillis - the number of milliseconds to specify that cache entries subsequently added without an expiry will live, EXPIRY_DEFAULT to indicate that the OverflowMap's default expiry be used (which is to never automatically expire values), or EXPIRY_NEVER to specify that cache entries subsequently added without an expiry will never expire

getSize

protected int getSize()

Obtain the number of entries in the OverflowMap.

Returns:

the cached size of the OverflowMap

setSize

protected void setSize(int cItems)

Update the number of entries in the OverflowMap.

Parameters:

cItems - the cached size of the OverflowMap

adjustSize

protected void adjustSize(int cItems)

Adjust the number of entries in the OverflowMap.

Parameters:

cItems - the number of items to adjust the cached size of the OverflowMap by, for example +1 or -1

getCacheStatistics

public CacheStatistics getCacheStatistics()

Returns the CacheStatistics for this cache.

Returns:

a CacheStatistics object

getThreadGate

protected ThreadGate getThreadGate()

Obtain the ThreadGate for managing key-level and Collection-level operations against the Map, versus Map-level operations themselves.

Returns:

the ThreadGate for the OverflowMap

getStatusMap

protected Map getStatusMap()

Obtain the Map of Status objects for entries managed by this Overflow Map. There will be a Status object for each entry in the front map, and a Status object for each key that has a current operation underway.

Returns:

the Map of Status objects

getExpiryArray

protected LongArray getExpiryArray()

Obtain the array of keys that have an expiration, indexed by expiration times.

Returns:

a sparse LongArray keyed by expiry time with a corresponding value of a set of keys that expire at that time

setExpiryArray

protected void setExpiryArray(LongArray laExpiry)

Specify the array of keys that have an expiration, indexed by expiration times.

Parameters:

laExpiry - a LongArray to use to keep track of what expires when

getFrontMapListener

protected MapListener getFrontMapListener()

Get the MapListener for the front map.

Returns:

the MapListener for the front map

setFrontMapListener

protected void setFrontMapListener(MapListener listener)

Specify the MapListener for the front map.

The caller is required to manage all of the thread concurrency issues associated with modifying the listener.

Parameters:

listener - the MapListener for the front map

getBackMapListener

protected MapListener getBackMapListener()

Get the MapListener for the back map.

Returns:

the MapListener for the back map

setBackMapListener

protected void setBackMapListener(MapListener listener)

Specify the MapListener for the back map.

The caller is required to manage all of the thread concurrency issues associated with modifying the listener.

Parameters:

listener - the MapListener for the back map

getDeferredList

protected List getDeferredList()

Obtain the List of keys that may have deferred events.

Returns:

the List of keys of deferred-event Status objects

isNullValuesAllowed

public boolean isNullValuesAllowed()

Determine if null values are permitted. By default, they are not.

Returns:

true iff null values are permitted

setNullValuesAllowed

public void setNullValuesAllowed(boolean fAllowNulls)

Specify whether null values are permitted.

Parameters:

fAllowNulls - pass true to allow null values; false to disallow

isExpiryEnabled

public boolean isExpiryEnabled()

Determine if this OverflowMap supports entry expiry.

Returns:

true iff the entry expiry feature is supported

setExpiryEnabled

public void setExpiryEnabled(boolean fEnableExpiry)

Specify whether or not entry expiry is supported. Since there is a per-entry (memory) cost just to support the expiry feature, and since there is additional memory cost (and a small performance cost) to keep track of entries that are set to expire, this feature is made optional.

Note that this feature must be enabled before populating the cache.

Parameters:

fEnableExpiry - pass true to enable entry expiry, false to disable it

isFrontPutBlind

public boolean isFrontPutBlind()

Determine if the front Map is more efficiently updated using putAll. (The use of putAll instead of put is called put-blind because it does not return a value.)

Returns:

true iff the use of the put method should be avoided when updating the front Map, and putAll should be used instead

setFrontPutBlind

public void setFrontPutBlind(boolean fUseFrontPutAll)

Specify whether the front Map is more efficiently updated using putAll.

Parameters:

fUseFrontPutAll - pass true to allow null values; false to disallow

beginKeyProcess

protected OverflowMap.Status beginKeyProcess(Object oKey)

Block until a key is available for processing, and return the Status object for that key. The caller is then expected to perform its processing, during which time events against the Map Entry may occur. Note that those events can occur on threads other than the current thread; when this current thread can no longer handle events from other threads, it must call OverflowMap.Status.closeProcessing() and then perform its final adjustments to the Status data structure, handling any events that were queued in the meantime on the Status. After completing the processing during this "quiet period" in which all other threads are prevented from accessing this entry or handling events for this entry, then the caller must call endKeyProcess(java.lang.Object, com.tangosol.net.cache.OverflowMap.Status) passing the Status object returned from this method.

Parameters:

oKey - the key to process

Returns:

the Status object for the specified key

endKeyProcess

protected void endKeyProcess(Object oKey,
                             OverflowMap.Status status)

Finish the processing of a single key.

Parameters:

status - the Status object returned from the call to beginKeyProcess(java.lang.Object)

beginMapProcess

protected void beginMapProcess()

Block until this thread has exclusive access to perform operations against the OverflowMap.

endMapProcess

protected void endMapProcess()

Release exclusive access for the OverflowMap.

prepareStatus

protected boolean prepareStatus(Object oKey,
                                OverflowMap.Status status)

Validate the status and process any deferred events or pending expiry.

Parameters:

oKey - the entry key

status - the Status object for the entry

Returns:

true iff the Status is in the processing state and oready to be used

onFrontEvent

protected void onFrontEvent(MapEvent evt)

Either handle an event by turning it over to another thread that is processing the key specified by the event, or take responsibility on this thread for deferring the event and registering its immediate side-effects.

onBackEvent

protected void onBackEvent(MapEvent evtBack)

Handle an event occuring against the "back" map.

Parameters:

evtBack - an event from the back map

mergeEvents

protected static MapEvent mergeEvents(MapEvent evtOld,
                                      MapEvent evtNew)

Merge two events that have been raised in sequence from a given map.

Parameters:

evtOld - the first event

evtNew - the second event

Returns:

the merged event

getLatestOldValue

protected static Object getLatestOldValue(MapEvent evt)

Obtain the latest old value from the passed event. The latest old value is the value that must be retained upon the eviction of data from the front map.

Parameters:

evt - an event (which may be a HistoricCacheEvent)

Returns:

the latest old value from the event

processEvent

protected void processEvent(OverflowMap.Status status,
                            MapEvent evt)

Process an arbitrary event that has occurred against either the front or back map.

Parameters:

status - the Status object representing the Overflow Map's entry against which the event was raised

evt - the MapEvent to process

processFrontEvent

protected void processFrontEvent(OverflowMap.Status status,
                                 MapEvent evtFront)

Process an event. The Status must already be owned by this thread and in the processing or committing state.

Parameters:

evtFront - the event to process; may be null

processBackEvent

protected void processBackEvent(OverflowMap.Status status,
                                MapEvent evtBack)

Process an event. The Status must already be owned by this thread and in the processing or committing state.

Parameters:

evtBack - the event to process; may be null

processDeferredEvents

protected void processDeferredEvents(boolean fProcessAll)

Process deferred events, if there are any.

Parameters:

fProcessAll - pass true to process all pending events, false to process just a fair portion of them

closeStatus

protected void closeStatus(OverflowMap.Status status)

Helper method to close a Status, processing any pending events as part of the process.

Parameters:

status - the Status object to close

releaseClosedStatus

protected void releaseClosedStatus(Object oKey)

Helper method to encapsulate the release of a Status object on which closeProcessing() has already been called.

Parameters:

oKey - the entry key

getMapListenerSupport

protected MapListenerSupport getMapListenerSupport()

Accessor for the MapListenerSupport for sub-classes.

Returns:

the MapListenerSupport, or null if there are no listeners

hasListeners

protected boolean hasListeners()

Determine if the OverflowMap has any listeners at all.

Returns:

true iff this OverflowMap has at least one MapListener

dispatchEvent

protected void dispatchEvent(OverflowMap.Status status,
                             int nId,
                             Object oKey,
                             Object oValueOld,
                             Object oValueNew,
                             boolean fSynthetic)

Dispatch an event containing the passed event information.

Parameters:

status - the Status for the entry

nId - this event's id

oKey - the key into the map

oValueOld - the old value

oValueNew - the new value

fSynthetic - true iff the event is caused by the cache internal processing such as eviction or loading

dispatchEvent

protected void dispatchEvent(OverflowMap.Status status,
                             MapEvent evt)

Dispatch the passed event.

Parameters:

status - the Status for the entry

evt - a MapEvent object

isSynthetic

protected static boolean isSynthetic(MapEvent evt)

Helper method to determine if an event is synthetic.

Parameters:

evt - a Map Event

Returns:

true if the event is a synthetic cache event

registerExpiry

protected void registerExpiry(Object oKey,
                              long ldtExpire)

Register an expiry for the specified key.

Parameters:

oKey - the key of the entry to expire

ldtExpire - the time to expire the entry

unregisterExpiry

protected void unregisterExpiry(Object oKey,
                                long ldtExpire)

Unregister the specified key expiry that is registered to expire at the specified time.

Parameters:

oKey - the key that is set to expire

ldtExpire - the time that the key is set to expire

verifyNoNulls

protected static void verifyNoNulls(Collection collection,
                                    String sAssert)

Check the passed collection for nulls, and fail if it contains any.

Parameters:

collection - a Collection

sAssert - the human-readable description of the error if any nulls are found in the passed Collection

putOne

protected static void putOne(Map map,
                             Object oKey,
                             Object oValue,
                             boolean fPutBlind)

Helper to put a value into a map using either the put or putAll method.

Parameters:

map - the Map to put into

oKey - the key to put

oValue - the value to put

fPutBlind - true to use the putBlind optimization

evict

public void evict()

Flush items that have expired.

Since:

Coherence 3.2

evict

protected static void evict(Map map)

If the passed Map supports it, evict its expired data.

Parameters:

map - a Map that may or may not support the requesting of an eviction of expired data

Since:

Coherence 3.2

warnMissingEvent

protected void warnMissingEvent(Object oKey,
                                int nId,
                                boolean fFront)

An expected event did not get raised. Try to report it to the log.

Parameters:

oKey - the key for which an event is missing

nId - the event type that is missing

fFront - true if the event was expected to come from the front map, false if from the back map

warnUnfathomable

protected void warnUnfathomable(MapEvent evt)

Something totally inexplicable has occurred. Try to report it to the log.

Parameters:

evt - the event that cannot be explained

warnEventSequence

protected static void warnEventSequence(MapEvent evtOld,
                                        MapEvent evtNew)

Issue a one-time warning that events are being received in an order than cannot be explained by normal operation according to the contracts expected by this OverflowMap.

Parameters:

evtOld - the previous (potentially amalgamated) event

evtNew - the new event

instantiateEntrySet

protected Set instantiateEntrySet()

Factory pattern: Create a Set that represents the entries in the Map.

Overrides:

instantiateEntrySet in class AbstractKeySetBasedMap

Returns:

a new instance of Set that represents the entries in the Map

instantiateInternalKeySet

protected Set instantiateInternalKeySet()

Factory pattern: Create a read-only Set of keys in the Overflow Map

Returns:

a new instance of Set that represents the keys in the Map

instantiateStatus

protected OverflowMap.Status instantiateStatus()

Factory method: Instantiate a Status object.

Returns:

a new Status object

instantiateFrontMapListener

protected MapListener instantiateFrontMapListener()

Factory pattern: Front Map Listener.

Returns:

a new instance of the listener for the front map

instantiateBackMapListener

protected MapListener instantiateBackMapListener()

Factory pattern: Back Map Listener.

Returns:

a new instance of the listener for the back map