package org.jctools_voltpatches.queues;
/**
* This interface is provided for monitoring purposes only and is only available on queues where it is easy to
* provide it. The producer/consumer progress indicators usually correspond with the number of elements
* offered/polled, but they are not guaranteed to maintain that semantic.
*
* @author nitsanw
*
*/
public interface QueueProgressIndicators {
/**
* This method has no concurrent visibility semantics. The value returned may be negative. Under normal
* circumstances 2 consecutive calls to this method can offer an idea of progress made by producer threads
* by subtracting the 2 results though in extreme cases (if producers have progressed by more than 2^64)
* this may also fail.<br/>
* This value will normally indicate number of elements passed into the queue, but may under some
* circumstances be a derivative of that figure. This method should not be used to derive size or
* emptiness.
*
* @return the current value of the producer progress index
*/
long currentProducerIndex();
/**
* This method has no concurrent visibility semantics. The value returned may be negative. Under normal
* circumstances 2 consecutive calls to this method can offer an idea of progress made by consumer threads
* by subtracting the 2 results though in extreme cases (if consumers have progressed by more than 2^64)
* this may also fail.<br/>
* This value will normally indicate number of elements taken out of the queue, but may under some
* circumstances be a derivative of that figure. This method should not be used to derive size or
* emptiness.
*
* @return the current value of the consumer progress index
*/
long currentConsumerIndex();
}