org.opennms.core.concurrent
Class RunnableConsumerThreadPool.SizingFifoQueue

java.lang.Object
  org.opennms.core.queue.FifoQueueImpl
      org.opennms.core.concurrent.RunnableConsumerThreadPool.SizingFifoQueue

All Implemented Interfaces:

ClosableFifoQueue, FifoQueue

Enclosing class:

RunnableConsumerThreadPool

private class RunnableConsumerThreadPool.SizingFifoQueue

extends FifoQueueImpl

implements ClosableFifoQueue

This class is used to create a queue that auto adjust the number of threads in the pool. Each time an addition or removal of queue elements occur the pool will be adjusted. This will cause some synchronization overhead, but it should be correct implementation.

To avoid the condition of toggleing a single thread the lo and hi water marks should have a large cushion between them.

Author:

Brian Weaver, OpenNMS

Field Summary

private boolean

m_isClosed Determines if the queue is open or closed.

Fields inherited from class org.opennms.core.queue.FifoQueueImpl

Constructor Summary

private

RunnableConsumerThreadPool.SizingFifoQueue()

Method Summary

void	add(java.lang.Object element) Inserts a new element into the queue.
boolean	add(java.lang.Object element, long timeout) Inserts a new element into the queue.
private void	adjust() Adjust the size of the thread pool based on the ratio of queue elements to threads.
void	close() Closes a currently open queue.
boolean	isClosed() Returns true if the queue is currently closed.
boolean	isOpen() Returns true if the queue is currently open.
void	open() Ensures that the queue is open and new elements can be added to the queue.
java.lang.Object	remove() Removes the oldest element from the queue.
java.lang.Object	remove(long timeout) Removes the next element from the queue if one becomes available before the timeout expires.

Methods inherited from class org.opennms.core.queue.FifoQueueImpl

isEmpty, size

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface org.opennms.core.queue.FifoQueue

isEmpty, size

Field Detail

m_isClosed

private volatile boolean m_isClosed

Determines if the queue is open or closed. If the queue is closed then an exception is thrown on queue additions. Also, queue removals will cause a queue exception if the queue is empty.

Constructor Detail

RunnableConsumerThreadPool.SizingFifoQueue

private RunnableConsumerThreadPool.SizingFifoQueue()

Method Detail

adjust

private void adjust()

Adjust the size of the thread pool based on the ratio of queue elements to threads. The thread pool is adjusted by the lo and hi water marks which are a ratio of elements to threads.

isOpen

public boolean isOpen()

Returns true if the queue is currently open.

Specified by:

isOpen in interface ClosableFifoQueue

Returns:

True if the queue is open.

isClosed

public boolean isClosed()

Returns true if the queue is currently closed.

Specified by:

isClosed in interface ClosableFifoQueue

Returns:

True if the queue is closed.

close

public void close()
           throws FifoQueueException

Closes a currently open queue. When a queue is closed is should still allow elements already in the queue to be removed, but new elements should not be added.

Specified by:

close in interface ClosableFifoQueue

Throws:

FifoQueueException - Thrown if an error occurs closing the queue.

open

public void open()
          throws FifoQueueException

Ensures that the queue is open and new elements can be added to the queue.

Specified by:

open in interface ClosableFifoQueue

Throws:

FifoQueueException - Thrown if an error occurs opening the queue.

add

public void add(java.lang.Object element)
         throws FifoQueueException,
                java.lang.InterruptedException

Inserts a new element into the queue.

Specified by:

add in interface FifoQueue

Overrides:

add in class FifoQueueImpl

Parameters:

element - The object to append to the queue.

Throws:

FifoQueueException - Thrown if a queue error occurs.

java.lang.InterruptedException - Thrown if the thread is interrupted.

add

public boolean add(java.lang.Object element,
                   long timeout)
            throws FifoQueueException,
                   java.lang.InterruptedException

Inserts a new element into the queue. If the queue has reached an implementation limit and the timeout expires, then a false value is returned to the caller.

Specified by:

add in interface FifoQueue

Overrides:

add in class FifoQueueImpl

Parameters:

element - The object to append to the queue.

timeout - The time to wait on the insertion to succeed.

Returns:

True if the element was successfully added to the queue before the timeout expired, false otherwise.

Throws:

FifoQueueException - Thrown if a queue error occurs.

java.lang.InterruptedException - Thrown if the thread is interrupted.

remove

public java.lang.Object remove()
                        throws FifoQueueException,
                               java.lang.InterruptedException

Removes the oldest element from the queue.

Specified by:

remove in interface FifoQueue

Overrides:

remove in class FifoQueueImpl

Returns:

The oldest object in the queue.

Throws:

FifoQueueException - Thrown if a queue error occurs.

java.lang.InterruptedException - Thrown if the thread is interrupted.

remove

public java.lang.Object remove(long timeout)
                        throws FifoQueueException,
                               java.lang.InterruptedException

Removes the next element from the queue if one becomes available before the timeout expires. If the timeout expires before an element is available then a null reference is returned to the caller.

Specified by:

remove in interface FifoQueue

Overrides:

remove in class FifoQueueImpl

Parameters:

timeout - The time to wait on an object to be available.

Returns:

The oldest object in the queue, or null if one is not available.

Throws:

FifoQueueException - Thrown if a queue error occurs.

java.lang.InterruptedException - Thrown if the thread is interrupted.