Interface MessagePassingQueue<T>

Type Parameters:
T - the event/message type
All Known Implementing Classes:
AtomicReferenceArrayQueue, BaseLinkedAtomicQueue, BaseLinkedAtomicQueueConsumerNodeRef, BaseLinkedAtomicQueuePad0, BaseLinkedAtomicQueuePad1, BaseLinkedAtomicQueuePad2, BaseLinkedAtomicQueueProducerNodeRef, BaseLinkedQueue, BaseLinkedQueueConsumerNodeRef, BaseLinkedQueuePad0, BaseLinkedQueuePad1, BaseLinkedQueuePad2, BaseLinkedQueueProducerNodeRef, BaseMpscLinkedArrayQueue, BaseMpscLinkedAtomicArrayQueue, BaseSpscLinkedArrayQueue, BaseSpscLinkedAtomicArrayQueue, ConcurrentCircularArrayQueue, ConcurrentSequencedCircularArrayQueue, FFBuffer, FFBufferConsumerField, FFBufferL1Pad, FFBufferL2Pad, FFBufferL3Pad, FFBufferProducerField, MpmcArrayQueue, MpmcArrayQueueConsumerIndexField, MpmcArrayQueueL1Pad, MpmcArrayQueueL2Pad, MpmcArrayQueueL3Pad, MpmcArrayQueueProducerIndexField, MpmcAtomicArrayQueue, MpmcAtomicArrayQueueConsumerIndexField, MpmcAtomicArrayQueueL1Pad, MpmcAtomicArrayQueueL2Pad, MpmcAtomicArrayQueueL3Pad, MpmcAtomicArrayQueueProducerIndexField, MpmcUnboundedXaddArrayQueue, MpscArrayQueue, MpscArrayQueueConsumerIndexField, MpscArrayQueueL1Pad, MpscArrayQueueL2Pad, MpscArrayQueueL3Pad, MpscArrayQueueMidPad, MpscArrayQueueProducerIndexField, MpscArrayQueueProducerLimitField, MpscAtomicArrayQueue, MpscAtomicArrayQueueConsumerIndexField, MpscAtomicArrayQueueL1Pad, MpscAtomicArrayQueueL2Pad, MpscAtomicArrayQueueL3Pad, MpscAtomicArrayQueueMidPad, MpscAtomicArrayQueueProducerIndexField, MpscAtomicArrayQueueProducerLimitField, MpscBlockingConsumerArrayQueue, MpscChunkedArrayQueue, MpscChunkedArrayQueueColdProducerFields, MpscChunkedAtomicArrayQueue, MpscChunkedAtomicArrayQueueColdProducerFields, MpscCompoundQueue, MpscCompoundQueueColdFields, MpscCompoundQueueConsumerQueueIndex, MpscCompoundQueueL0Pad, MpscCompoundQueueMidPad, MpscGrowableArrayQueue, MpscGrowableAtomicArrayQueue, MpscLinkedAtomicQueue, MpscLinkedQueue, MpscRelaxedArrayQueue, MpscRelaxedAtomicArrayQueue, MpscSequencedArrayQueue, MpscSequencedArrayQueueConsumerField, MpscSequencedArrayQueueL1Pad, MpscSequencedArrayQueueL2Pad, MpscSequencedArrayQueueProducerField, MpscUnboundedArrayQueue, MpscUnboundedAtomicArrayQueue, MpscUnboundedXaddArrayQueue, MpUnboundedXaddArrayQueue, SequencedAtomicReferenceArrayQueue, SpmcArrayQueue, SpmcArrayQueueConsumerIndexField, SpmcArrayQueueL1Pad, SpmcArrayQueueL2Pad, SpmcArrayQueueL3Pad, SpmcArrayQueueMidPad, SpmcArrayQueueProducerIndexCacheField, SpmcArrayQueueProducerIndexField, SpmcAtomicArrayQueue, SpmcAtomicArrayQueueConsumerIndexField, SpmcAtomicArrayQueueL1Pad, SpmcAtomicArrayQueueL2Pad, SpmcAtomicArrayQueueL3Pad, SpmcAtomicArrayQueueMidPad, SpmcAtomicArrayQueueProducerIndexCacheField, SpmcAtomicArrayQueueProducerIndexField, SpscArrayQueue, SpscArrayQueueColdField, SpscArrayQueueConsumerIndexField, SpscArrayQueueL1Pad, SpscArrayQueueL2Pad, SpscArrayQueueL3Pad, SpscArrayQueueProducerIndexFields, SpscAtomicArrayQueue, SpscAtomicArrayQueueColdField, SpscAtomicArrayQueueConsumerIndexField, SpscAtomicArrayQueueL1Pad, SpscAtomicArrayQueueL2Pad, SpscAtomicArrayQueueL3Pad, SpscAtomicArrayQueueProducerIndexFields, SpscChunkedArrayQueue, SpscChunkedAtomicArrayQueue, SpscGrowableArrayQueue, SpscGrowableAtomicArrayQueue, SpscLinkedAtomicQueue, SpscLinkedQueue, SpscUnboundedArrayQueue, SpscUnboundedAtomicArrayQueue

public interface MessagePassingQueue<T>
Message passing queues are intended for concurrent method passing. A subset of Queue methods are provided with the same semantics, while further functionality which accomodates the concurrent usecase is also on offer.

Message passing queues provide happens before semantics to messages passed through, namely that writes made by the producer before offering the message are visible to the consuming thread after the message has been polled out of the queue.

  • Field Details

  • Method Details

    • offer

      boolean offer(T e)
      Called from a producer thread subject to the restrictions appropriate to the implementation and according to the Queue.offer(Object) interface.
      Parameters:
      e - not null, will throw NPE if it is
      Returns:
      true if element was inserted into the queue, false iff full
    • poll

      T poll()
      Called from the consumer thread subject to the restrictions appropriate to the implementation and according to the Queue.poll() interface.
      Returns:
      a message from the queue if one is available, null iff empty
    • peek

      T peek()
      Called from the consumer thread subject to the restrictions appropriate to the implementation and according to the Queue.peek() interface.
      Returns:
      a message from the queue if one is available, null iff empty
    • size

      int size()
      This method's accuracy is subject to concurrent modifications happening as the size is estimated and as such is a best effort rather than absolute value. For some implementations this method may be O(n) rather than O(1).
      Returns:
      number of messages in the queue, between 0 and Integer.MAX_VALUE but less or equals to capacity (if bounded).
    • clear

      void clear()
      Removes all items from the queue. Called from the consumer thread subject to the restrictions appropriate to the implementation and according to the Collection.clear() interface.
    • isEmpty

      boolean isEmpty()
      This method's accuracy is subject to concurrent modifications happening as the observation is carried out.
      Returns:
      true if empty, false otherwise
    • capacity

      int capacity()
      Returns:
      the capacity of this queue or UNBOUNDED_CAPACITY if not bounded
    • relaxedOffer

      boolean relaxedOffer(T e)
      Called from a producer thread subject to the restrictions appropriate to the implementation. As opposed to Queue.offer(Object) this method may return false without the queue being full.
      Parameters:
      e - not null, will throw NPE if it is
      Returns:
      true if element was inserted into the queue, false if unable to offer
    • relaxedPoll

      T relaxedPoll()
      Called from the consumer thread subject to the restrictions appropriate to the implementation. As opposed to Queue.poll() this method may return null without the queue being empty.
      Returns:
      a message from the queue if one is available, null if unable to poll
    • relaxedPeek

      T relaxedPeek()
      Called from the consumer thread subject to the restrictions appropriate to the implementation. As opposed to Queue.peek() this method may return null without the queue being empty.
      Returns:
      a message from the queue if one is available, null if unable to peek
    • drain

      int drain(MessagePassingQueue.Consumer<T> c, int limit)
      Remove up to limit elements from the queue and hand to consume. This should be semantically similar to:

      
         M m;
         int i = 0;
         for(;i < limit && (m = relaxedPoll()) != null; i++){
           c.accept(m);
         }
         return i;
       

      There's no strong commitment to the queue being empty at the end of a drain. Called from a consumer thread subject to the restrictions appropriate to the implementation.

      WARNING: Explicit assumptions are made with regards to MessagePassingQueue.Consumer.accept(T) make sure you have read and understood these before using this method.

      Returns:
      the number of polled elements
      Throws:
      IllegalArgumentException - c is null
      IllegalArgumentException - if limit is negative
    • fill

      int fill(MessagePassingQueue.Supplier<T> s, int limit)
      Stuff the queue with up to limit elements from the supplier. Semantically similar to:

      
         for(int i=0; i < limit && relaxedOffer(s.get()); i++);
       

      There's no strong commitment to the queue being full at the end of a fill. Called from a producer thread subject to the restrictions appropriate to the implementation. WARNING: Explicit assumptions are made with regards to MessagePassingQueue.Supplier.get() make sure you have read and understood these before using this method.

      Returns:
      the number of offered elements
      Throws:
      IllegalArgumentException - s is null
      IllegalArgumentException - if limit is negative
    • drain

      Remove all available item from the queue and hand to consume. This should be semantically similar to:
       M m;
       while((m = relaxedPoll()) != null){
       c.accept(m);
       }
       
      There's no strong commitment to the queue being empty at the end of a drain. Called from a consumer thread subject to the restrictions appropriate to the implementation.

      WARNING: Explicit assumptions are made with regards to MessagePassingQueue.Consumer.accept(T) make sure you have read and understood these before using this method.

      Returns:
      the number of polled elements
      Throws:
      IllegalArgumentException - c is null
    • fill

      Stuff the queue with elements from the supplier. Semantically similar to:
       while(relaxedOffer(s.get());
       
      There's no strong commitment to the queue being full at the end of a fill. Called from a producer thread subject to the restrictions appropriate to the implementation.

      Unbounded queues will fill up the queue with a fixed amount rather than fill up to oblivion. WARNING: Explicit assumptions are made with regards to MessagePassingQueue.Supplier.get() make sure you have read and understood these before using this method.

      Returns:
      the number of offered elements
      Throws:
      IllegalArgumentException - s is null
    • drain

      Remove elements from the queue and hand to consume forever. Semantically similar to:

        int idleCounter = 0;
        while (exit.keepRunning()) {
            E e = relaxedPoll();
            if(e==null){
                idleCounter = wait.idle(idleCounter);
                continue;
            }
            idleCounter = 0;
            c.accept(e);
        }
       

      Called from a consumer thread subject to the restrictions appropriate to the implementation.

      WARNING: Explicit assumptions are made with regards to MessagePassingQueue.Consumer.accept(T) make sure you have read and understood these before using this method.

      Throws:
      IllegalArgumentException - c OR wait OR exit are null
    • fill

      Stuff the queue with elements from the supplier forever. Semantically similar to:

       
        int idleCounter = 0;
        while (exit.keepRunning()) {
            E e = s.get();
            while (!relaxedOffer(e)) {
                idleCounter = wait.idle(idleCounter);
                continue;
            }
            idleCounter = 0;
        }
       
       

      Called from a producer thread subject to the restrictions appropriate to the implementation. The main difference being that implementors MUST assure room in the queue is available BEFORE calling MessagePassingQueue.Supplier.get(). WARNING: Explicit assumptions are made with regards to MessagePassingQueue.Supplier.get() make sure you have read and understood these before using this method.

      Throws:
      IllegalArgumentException - s OR wait OR exit are null