com.tangosol.net.cache
Class SimpleOverflowMap.Status

java.lang.Object
  com.tangosol.net.cache.SimpleOverflowMap.Status

Enclosing class:

SimpleOverflowMap

protected static class SimpleOverflowMap.Status
extends Object

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.

Field Summary

protected static int	STATE_MASK_FRONT Bitmask for entry in front.
protected static int	STATE_MASK_INSYNC Bitmask for value in front and back being in sync.
protected static int	STATE_MASK_RETAIN Bitmask for fields that would indicate that the Status must not be discarded.
protected static int	STATE_MASK_STATUS Bitmask for status (least significant three bits reserved).
protected static int	STATE_VALUE_RETAIN Bit values for fields that would indicate that the Status can be discarded.
protected static int	STATUS_AVAILABLE Status: The Status object exists and no thread is currently performing processing against the associated entry.
protected static int	STATUS_COMMITTING Status: The Status object represents an Entry that was very recently being processed, and is currently finalizing the results of that processing.
protected static int	STATUS_INVALIDATED Status: The Status object has been discarded.
protected static int	STATUS_PROCESSING Status: The Status object represents an Entry that is currently being processed.
protected static int	STATUS_RESERVED Status: The Status object has been reserved for processing by a thread but is not yet processing.

Constructor Summary

SimpleOverflowMap.Status()
Construct a Status object for a specific key.

Method Summary

MapEvent	closeProcessing() Finish the processing of the entry for which this Status exists and proceed to the commit phase.
protected boolean	commitAndMaybeInvalidate() Finish the commit for the entry for which this Status exists.
protected boolean	extractFlag(int nMask) Extract a particular masked flag from the state of the Status object.
protected int	extractState(int nMask) Extract a particular masked value from the state of the Status object.
String	getDescription() Assemble a human-readable description.
protected MapEvent	getFrontEvent() For internal use only, return the current event from the front Map.
Thread	getOwnerThread() Determine the thread that owns the Status object, if the Status object is processing or committing.
protected int	getState() Determine the state of the Status object.
protected int	getStatus() Determine the enumerated status of the Status object.
boolean	hasEvent() Determine if an event has occurred against the Entry for which this Status exists.
boolean	isAvailable() Determine if the Status object is available.
boolean	isBackUpToDate() Determine if the entry for which this Status exists has the same value in the front Map as in the back Map.
boolean	isCommitting() Determine if the Status object represents an Entry that has been processed and the results of that processing are being committed.
protected boolean	isDiscardable() Determine if this Status object can be discarded.
boolean	isEntryInFront() Determine if the entry for which this Status exists is present in the front map.
boolean	isOwnedByCurrentThread() Determine if the current thread owns this Status object.
boolean	isProcessing() Determine if the Status object represents an Entry that is currently being processed.
boolean	isReserved() Determine if the Status object is reserved.
boolean	isValid() Determine if the Status object is valid.
protected MapEvent	mergeEvents(MapEvent evtOld, MapEvent evtNew) Merge two events that have been raised in sequence from a given map.
boolean	registerFrontEvent(MapEvent evt) Register a MapEvent that has been raised by the front Map against the same key for which this Status object exists.
protected boolean	requestReservation() Attempt to reserve the Status by marking it as committing if it is available.
void	setBackUpToDate(boolean fUpToDate) Specify that the value stored in the back Map is known to be up to date (not needing to be written to the back if evicted from the front).
void	setEntryInFront(boolean fEntryInFront) Specify whether the entry for which this Status exists is present in the front map.
protected void	setFrontEvent(MapEvent evt) For internal use only, store the current event from the front Map.
protected void	setOwnerThread(Thread thread) Specify the thread that owns the Status object.
protected void	setState(int nState) Specify the state of the Status object.
protected void	setStatus(int nStatus) Determine the enumerated state of the Status object.
MapEvent	takeEvent() Obtain the most recent front Map event that has occurred against the Entry for which this Status exists.
String	toString() Returns a string representation of the object.
protected void	updateFlag(int nMask, boolean f) Update a particular masked flag within the state of the Status object.
protected void	updateState(int nMask, int nValue) Update a particular masked value within the state of the Status object.
protected MapEvent	useReservation() After having successfully made a reservation, this method completes the reservation process by setting the status to processing for the thread that made the reservation.
protected MapEvent	waitForAvailable() Wait for the Entry that this Status represents to become available.
protected void	waitForReservationDecision() Wait for the Entry that this Status represents to no longer be reserved.

Field Detail

STATE_MASK_STATUS

protected static final int STATE_MASK_STATUS

Bitmask for status (least significant three bits reserved).

See Also:

Constant Field Values

STATE_MASK_FRONT

protected static final int STATE_MASK_FRONT

Bitmask for entry in front.

See Also:

Constant Field Values

STATE_MASK_INSYNC

protected static final int STATE_MASK_INSYNC

Bitmask for value in front and back being in sync.

See Also:

Constant Field Values

STATUS_AVAILABLE

protected static final int STATUS_AVAILABLE

Status: The Status object exists and no thread is currently performing processing against the associated entry.

See Also:

Constant Field Values

STATUS_RESERVED

protected static final int STATUS_RESERVED

Status: The Status object has been reserved for processing by a thread but is not yet processing.

See Also:

Constant Field Values

STATUS_PROCESSING

protected static final int STATUS_PROCESSING

Status: The Status object represents an Entry that is currently being processed.

See Also:

Constant Field Values

STATUS_COMMITTING

protected static final int STATUS_COMMITTING

Status: The Status object represents an Entry that was very recently being processed, and is currently finalizing the results of that processing.

See Also:

Constant Field Values

STATUS_INVALIDATED

protected static final int STATUS_INVALIDATED

Status: The Status object has been discarded.

See Also:

Constant Field Values

STATE_MASK_RETAIN

protected static final int STATE_MASK_RETAIN

Bitmask for fields that would indicate that the Status must not be discarded.

See Also:

Constant Field Values

STATE_VALUE_RETAIN

protected static final int STATE_VALUE_RETAIN

Bit values for fields that would indicate that the Status can be discarded.

See Also:

Constant Field Values

Constructor Detail

SimpleOverflowMap.Status

public SimpleOverflowMap.Status()

Construct a Status object for a specific key.

Method Detail

getStatus

protected int getStatus()

Determine the enumerated status of the Status object. This value is intended for internal and debugging use only, and should have no meaning to any external consumer.

Returns:

a number corresponding to the enumeration of states as represented by the STATUS_*

setStatus

protected void setStatus(int nStatus)

Determine the enumerated state of the Status object. This value is intended for internal and debugging use only, and should have no meaning to any external consumer.

Parameters:

nStatus - a number corresponding to one of the enumeration represented by the STATUS_* constants

isValid

public boolean isValid()

Determine if the Status object is valid. A Status object can be discarded (no longer used), in which case it will not be valid.

Returns:

true iff the Status object is still valid

isAvailable

public boolean isAvailable()

Determine if the Status object is available. A Status object is available if it is valid and no thread is currently processing the entry for which this Status object exists.

Returns:

true iff the Status object is available

isReserved

public boolean isReserved()

Determine if the Status object is reserved.

Returns:

true iff the Status object is available

isProcessing

public boolean isProcessing()

Determine if the Status object represents an Entry that is currently being processed.

Returns:

true iff the entry represented by this Status object is being processed

isCommitting

public boolean isCommitting()

Determine if the Status object represents an Entry that has been processed and the results of that processing are being committed. The "committing" status implies that no other thread is allowed to do anything related to the entry that this Status represents.

Returns:

true iff the entry represented by this Status object is being committed

getOwnerThread

public Thread getOwnerThread()

Determine the thread that owns the Status object, if the Status object is processing or committing.

Returns:

the owning thread, or null

setOwnerThread

protected void setOwnerThread(Thread thread)

Specify the thread that owns the Status object. For internal use only.

Parameters:

thread - the owning thread, or null

isOwnedByCurrentThread

public boolean isOwnedByCurrentThread()

Determine if the current thread owns this Status object.

Returns:

true iff the current thread owns this Status object

isEntryInFront

public boolean isEntryInFront()

Determine if the entry for which this Status exists is present in the front map.

Returns:

true iff the entry is stored in the front map

setEntryInFront

public void setEntryInFront(boolean fEntryInFront)

Specify whether the entry for which this Status exists is present in the front map.

Parameters:

fEntryInFront - pass true if the entry is stored in the front map, false if not

isBackUpToDate

public boolean isBackUpToDate()

Determine if the entry for which this Status exists has the same value in the front Map as in the back Map.

Returns:

true iff the value exists in the back Map, and the value in the front Map is the same as the value in the back Map

setBackUpToDate

public void setBackUpToDate(boolean fUpToDate)

Specify that the value stored in the back Map is known to be up to date (not needing to be written to the back if evicted from the front).

getFrontEvent

protected MapEvent getFrontEvent()

For internal use only, return the current event from the front Map. All handling of synchronization etc. is the responsibility of the sub-class.

Returns:

the cummulative front Map event for the Entry represented by this Status object, or null if there were no events

setFrontEvent

protected void setFrontEvent(MapEvent evt)

For internal use only, store the current event from the front Map. All handling of synchronization etc. is the responsibility of the sub-class.

Parameters:

evt - the cummulative front Map event for the Entry represented by this Status object, or null to clear the event

hasEvent

public boolean hasEvent()

Determine if an event has occurred against the Entry for which this Status exists.

Returns:

true iff an event is held by the Status

takeEvent

public MapEvent takeEvent()

Obtain the most recent front Map event that has occurred against the Entry for which this Status exists.

Returns:

the cummulative front Map event for the Entry represented by this Status object, or null if there were no events

isDiscardable

protected boolean isDiscardable()

Determine if this Status object can be discarded.

This is an internal method.

Returns:

true iff this Status object can be discarded

getDescription

public String getDescription()

Assemble a human-readable description.

Returns:

a description of this Status object

toString

public String toString()

Returns a string representation of the object.

Returns:

a string representation of the object

waitForAvailable

protected MapEvent waitForAvailable()

Wait for the Entry that this Status represents to become available. Once it becomes available, the current thread will automatically become the owner and the status will be changed to "processing".

This is an internal method. It requires the caller to have synchronized on the Status object before calling this method.

Returns:

whatever event was deferred for this Status which the caller must handle

requestReservation

protected boolean requestReservation()

Attempt to reserve the Status by marking it as committing if it is available. If successful, the caller must subsequently either call useReservation() or commitAndMaybeInvalidate() (to cancel the reservation).

This is an internal method.

Returns:

true if the reservation was made successfull, false if another thread already owns this Status object

waitForReservationDecision

protected void waitForReservationDecision()

Wait for the Entry that this Status represents to no longer be reserved.

This is an internal method. It requires the caller to have synchronized on the Status object before calling this method.

useReservation

protected MapEvent useReservation()

After having successfully made a reservation, this method completes the reservation process by setting the status to processing for the thread that made the reservation.

This is an internal method.

Returns:

whatever event was deferred for this Status which the caller must handle

closeProcessing

public MapEvent closeProcessing()

Finish the processing of the entry for which this Status exists and proceed to the commit phase. The act of closing processing collects any side-effects to the corresponding front Map Entry (either from this or other threads) as a single event.

Returns:

all events that have occurred on this or other threads for the front Map Entry represented by this Status object while this Status object was "processing", or null if there were no events

commitAndMaybeInvalidate

protected boolean commitAndMaybeInvalidate()

Finish the commit for the entry for which this Status exists. If there are any threads waiting on the entry for which this Status exists, one will be notified that the Status is now available. If the entry for which this Status object exists is contained in the front Map, then it will proceed to the available phase. Otherwise, the Status will be invalidated and discarded from the Status registry.

This is an internal method. It requires the caller to have first synchronized on the registry (Map) that contains the Status objects and then to have synchronized on this Status object itself, in that explicit order. Failure to follow this rule will result in deadlock and/or exceptional conditions.

Returns:

true iff this Status object has invalidated itself

registerFrontEvent

public boolean registerFrontEvent(MapEvent evt)

Register a MapEvent that has been raised by the front Map against the same key for which this Status object exists. If an event has previously been registered, the previous and new event are merged into a single merged event that incorporates the data from both events.

For truly predictable behavior, this requires that the front Map implementation be synchronized during the raising of events, such that an event will only be raised from the front Map on one thread at a time. The event listener (for the overflow map) must then synchronize on this Status object (to verify that it is indeed valid before registering the event) and the register the event while holding that synchronization. If the registration returns a deferred indicator, then the

Parameters:

evt - the event that has occurred against an entry in the front Map with the same key which this Status object represents

Returns:

true iff the event processing has been deferred, implying that this Status object should be registered in a list of Status objects that have events that need to be handled

mergeEvents

protected 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

getState

protected int getState()

Determine the state of the Status object. This value is intended for internal and debugging use only, and should have no meaning to any external consumer.

Returns:

the bit-packed state of the Status object

setState

protected void setState(int nState)

Specify the state of the Status object. This value is intended for internal and debugging use only, and should have no meaning to any external consumer.

Parameters:

nState - the new bit-packed state for the Status object

extractState

protected int extractState(int nMask)

Extract a particular masked value from the state of the Status object.

Parameters:

nMask - the mask identifying the value

Returns:

the extracted value

updateState

protected void updateState(int nMask,
                           int nValue)

Update a particular masked value within the state of the Status object.

Parameters:

nMask - the mask of bits to store the value within

nValue - the value to store inside that mask

extractFlag

protected boolean extractFlag(int nMask)

Extract a particular masked flag from the state of the Status object.

Parameters:

nMask - the mask identifying the flag

Returns:

the extracted flag as a boolean

updateFlag

protected void updateFlag(int nMask,
                          boolean f)

Update a particular masked flag within the state of the Status object.

Parameters:

nMask - the mask of flag bit to store the flag within

f - the boolean value to store within that mask