Package com.tangosol.net.cache

Class ReadWriteBackingMap.ReadQueue

  • Enclosing class:
    ReadWriteBackingMap
    public class ReadWriteBackingMap.ReadQueue
extends com.tangosol.license.CoherenceCommunityEdition
    A queue of keys that should be read from the underlying CacheStore.
    Author:
    jh 2005.02.08

    • Constructor Detail

      • ReadQueue

        protected ReadQueue()
        Construct a ReadQueue.

    • Method Detail

      • add

        public boolean add​(Object oKey)
        Add a key to the queue. This method has no effect if the key is already queued.
        Parameters:
        oKey - the key object
        Returns:
        true if the key was added to the queue; false otherwise

      • peek

        public Object peek()
        Wait for a key to be added to the queue and return it without removing it from the queue.
        Returns:
        the next item in the queue (it will only return null when the backing map is no longer active)

      • peek

        public Object peek​(long cMillis)
        Wait for a key (up to the specified wait time) to be added to the queue and return it without removing it from the queue, or null if the specified wait time has passed).
        Parameters:
        cMillis - the number of ms to wait for a key in the queue; 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        the next item in the queue, or null if the wait time has passed or if the backing map is no longer active

      • remove

        public boolean remove​(Object oKey)
        Remove a key from the queue if the key is in the queue.
        Parameters:
        oKey - the key object
        Returns:
        true if the key was removed from the queue; false otherwise

      • select

        protected ReadWriteBackingMap.ReadLatch select​(long cWaitMillis)
        Select the next key from the refresh-ahead queue that is a candidate for an asynchronous load. A key is a candidate if it can be locked "quickly".

        This method performs the selection process by iterating through the refresh-ahead queue starting with the first key in the queue. If the queue is empty, this method will block until a key is added to the queue. A key is skipped if it cannot be locked within the specified wait time.

        If a candidate key is found, a new ReadLatch for the key is placed in the control map and returned; otherwise, null is returned.

        Parameters:
        cWaitMillis - the maximum amount of time (in milliseconds) to wait to select a key and acquire a latch on it; pass -1 to wait indefinitely
        Returns:
        a ReadLatch for the selected key or null if a candidate key was not found and latched within the specified time

      • clear

        public void clear()
        Remove all keys from the queue.

      • size

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

      • toString

        public String toString()
        For debugging purposes, present the queue in human-readable format.
        Overrides:
        toString in class com.tangosol.license.CoherenceCommunityEdition
        Returns:
        a String representation of this object

      • getKeyList

        protected List getKeyList()
        Return a list of keys in the queue.
        Returns:
        a list of keys in the queue

      • getKeyMap

        protected Map<Object,​com.tangosol.internal.tracing.Span> getKeyMap()
        Return a map of keys in the queue.

        Note: The map returned from this method is not thread-safe; therefore, a lock on this ReadQueue must be obtained before accessing the map

        Returns:
        a map of keys in the queue