Oracle® Coherence Java API Reference
v3.5

E14977-01

com.tangosol.net.cache
Class ReadWriteBackingMap.WriteQueue

java.lang.Object
  extended by CoherenceApplicationEdition
      extended by com.tangosol.net.cache.ReadWriteBackingMap.WriteQueue
Enclosing class:
ReadWriteBackingMap

public class ReadWriteBackingMap.WriteQueue
extends CoherenceApplicationEdition

A queue that only releases entries after a configurable period of time.

Author:
cp 2002.10.22

Nested Class Summary
 class ReadWriteBackingMap.WriteQueue.Entry
          A queue entry that is scheduled to come out of the front of the queue no earlier than some specific point in time.
 
Constructor Summary
protected ReadWriteBackingMap.WriteQueue()
          Construct a WriteQueue that holds write-behind entries.
 
Method Summary
 java.lang.Object add(java.lang.Object oKey, java.lang.Object oValue)
          Add an entry to the queue.
 java.lang.Object checkPending(java.lang.Object oKey)
          Check for an item known to the WriteBehind queue.
 void clearPending()
          Clear the map of pending entries.
 boolean containsKey(java.lang.Object oKey)
           
protected  long getCutoffMillis()
          Determine the time before which all entries that were added are now eligable for removing from the queue.
 long getDelayMillis()
           
 int getDelaySeconds()
           
protected  java.util.Map getEntryMap()
           
protected  java.util.List getKeyList()
           
protected  java.util.Map getPendingMap()
          Obtain a map of entries removed from the queue, but not yet persisted to the underlying datastore.
protected  ReadWriteBackingMap.WriteQueue.Entry instantiateEntry(java.lang.Object oKey)
          Factory pattern: instantiate a queue entry.
 boolean isEmpty()
           
 java.util.Map.Entry remove()
          Wait for item in the queue to ripen (to be ready to be removed), and when there is one and it is ripe, then remove and return it.
 java.util.Map.Entry remove(long cMillis)
          Wait for the next item in the queue to ripen (to be ready to be removed), and remove and return it, or return null if the specified wait time has passed.
 java.util.Map.Entry remove(java.lang.Object oKey)
          Remove a key from the queue if the key is in the queue.
 java.util.Map.Entry removeImmediate()
          Remove the first key from the queue immediately.
 java.util.Map.Entry removeNoWait()
          Check for a ripe or soft-ripe item in the queue, and if there is one, return it; otherwise, return null.
 void setDelayMillis(long cMillis)
          Specify the number of millseconds that an entry added to the queue will sit in the queue before being removable ("ripe").
 void setDelaySeconds(int cSeconds)
          Specify the number of seconds that an entry added to the queue will sit in the queue before being removable ("ripe").
 int size()
           
 

Constructor Detail

ReadWriteBackingMap.WriteQueue

protected ReadWriteBackingMap.WriteQueue()
Construct a WriteQueue that holds write-behind entries.

Method Detail

getDelaySeconds

public int getDelaySeconds()
Returns:
the number of seconds that an entry added to the queue will sit in the queue before being removable ("ripe")

setDelaySeconds

public void setDelaySeconds(int cSeconds)
Specify the number of seconds that an entry added to the queue will sit in the queue before being removable ("ripe").

Parameters:
cSeconds - the number of seconds to wait before allowing an entry to be removed from the queue

getDelayMillis

public long getDelayMillis()
Returns:
the number of milliseconds that an entry added to the queue will sit in the queue before being removable ("ripe")
Since:
Coherence 3.4

setDelayMillis

public void setDelayMillis(long cMillis)
Specify the number of millseconds that an entry added to the queue will sit in the queue before being removable ("ripe").

Parameters:
cMillis - the number of milliseconds to wait before allowing an entry to be removed from the queue
Since:
Coherence 3.4

add

public java.lang.Object add(java.lang.Object oKey,
                            java.lang.Object oValue)
Add an entry to the queue.

Parameters:
oKey - the key object
oValue - the value object
Returns:
the old value of the existing entry, if such an entry existed at the time this method was invoked; null otherwise

remove

public java.util.Map.Entry remove(java.lang.Object oKey)
Remove a key from the queue if the key is in the queue. This method is used, for example, if an item has actually been removed from the backing map.

Parameters:
oKey - the key object
Returns:
the corresponding entry in the queue or null if the specified key was not in the queue

removeImmediate

public java.util.Map.Entry removeImmediate()
Remove the first key from the queue immediately.

Returns:
the first entry in the queue or null if the queue is empty

remove

public java.util.Map.Entry remove()
Wait for item in the queue to ripen (to be ready to be removed), and when there is one and it is ripe, then remove and return it.

Returns:
the next item in the queue (it will only return null when the backing map is no longer active)

remove

public java.util.Map.Entry remove(long cMillis)
Wait for the next item in the queue to ripen (to be ready to be removed), and remove and return it, or return null if the specified wait time has passed.

Parameters:
cMillis - the number of ms to wait for an entry to ripen; pass -1 to wait indefinitely or 0 for no wait
Returns:
the next item in the queue, or null if the wait time has passed or if the backing map is no longer active

removeNoWait

public java.util.Map.Entry removeNoWait()
Check for a ripe or soft-ripe item in the queue, and if there is one, return it; otherwise, return null.

Unlike the remove(java.lang.Object) method, this method will also remove soft-ripe items as calculated using the write-batch factor. A soft-ripe item is an item that has been in the write-behind queue for at least the following duration:

 D' = (1.0 - F)*D
where:
 D = write-behind delay
 F = write-batch factor

Returns:
the next item in the queue if one is ripe or soft-ripe and if the backing map is active, otherwise null

size

public int size()
Returns:
the length of the queue

isEmpty

public boolean isEmpty()
Returns:
true if and only if the queue contains no items

containsKey

public boolean containsKey(java.lang.Object oKey)
Parameters:
oKey - the key to look for
Returns:
true if and only if the queue contains the specified key

checkPending

public java.lang.Object checkPending(java.lang.Object oKey)
Check for an item known to the WriteBehind queue.

Parameters:
oKey - the key object to look for
Returns:
a value from the queue or a pending map

clearPending

public void clearPending()
Clear the map of pending entries.


getEntryMap

protected java.util.Map getEntryMap()
Returns:
the set of items in the queue

getKeyList

protected java.util.List getKeyList()
Returns:
the list of items in the queue

getPendingMap

protected java.util.Map getPendingMap()
Obtain a map of entries removed from the queue, but not yet persisted to the underlying datastore. The returned map is not thread safe, so all access to its content must be synchronized by the caller.

Returns:
the map of items not yet persisted to the underlying datastore

getCutoffMillis

protected long getCutoffMillis()
Determine the time before which all entries that were added are now eligable for removing from the queue. Any entry whose "when-added" time falls on or before the cutoff is considered to be "ripe".

Returns:
the millisecond time value related to the system time from System.currentTimeMillis() to compare to entry when-added values to determine which entries are ripe

instantiateEntry

protected ReadWriteBackingMap.WriteQueue.Entry instantiateEntry(java.lang.Object oKey)
Factory pattern: instantiate a queue entry.

Parameters:
oKey - the key for the new entry
Returns:
a new Entry

Oracle® Coherence Java API Reference
v3.5

E14977-01

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