com.hazelcast.internal.util.concurrent

Class MPSCQueue<E>

java.lang.Object

java.util.AbstractCollection<E>

java.util.AbstractQueue<E>

com.hazelcast.internal.util.concurrent.MPSCQueue<E>

Type Parameters:

E - the type of elements held in this collection

All Implemented Interfaces:

Iterable<E>, Collection<E>, BlockingQueue<E>, Queue<E>

public final class MPSCQueue<E>
extends AbstractQueue<E>
implements BlockingQueue<E>

Multi producer single consumer queue. This queue has a configurable IdleStrategy so if there is nothing to take, the thread can idle and eventually can do the more expensive blocking. The blocking is especially a concern for the putting thread, because it needs to notify the blocked thread.

This MPSCQueue is based on 2 stacks; so the items are put in a reverse order by the putting thread, and by the taking thread they are reversed in order again so that the original ordering is restored. Using this approach, if there are multiple items on the stack, the owning thread can take them all using a single CAS. Once this is done, the owning thread can process them one by one and doesn't need to contend with the putting threads; reducing contention.

Constructor Summary

Constructors

Constructor and Description
MPSCQueue(IdleStrategy idleStrategy) Creates a new MPSCQueue with the provided IdleStrategy.
MPSCQueue(Thread consumerThread, IdleStrategy idleStrategy) Creates a new MPSCQueue with the provided IdleStrategy and consumer thread.

Method Summary

Modifier and Type	Method and Description
void	clear() .
int	drainTo(Collection<? super E> c)
int	drainTo(Collection<? super E> c, int maxElements)
boolean	isEmpty()
Iterator<E>	iterator()
boolean	offer(E item)
boolean	offer(E e, long timeout, TimeUnit unit)
E	peek()
E	poll()
E	poll(long timeout, TimeUnit unit)
void	put(E e)
int	remainingCapacity()
void	setConsumerThread(Thread consumerThread) Sets the consumer thread.
int	size() .
E	take()

Methods inherited from class java.util.AbstractQueue

add, addAll, element, remove

Methods inherited from class java.util.AbstractCollection

contains, containsAll, remove, removeAll, retainAll, toArray, toArray, toString

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.util.concurrent.BlockingQueue

add, contains, remove

Methods inherited from interface java.util.Queue

element, remove

Methods inherited from interface java.util.Collection

addAll, containsAll, equals, hashCode, parallelStream, removeAll, removeIf, retainAll, spliterator, stream, toArray, toArray

Methods inherited from interface java.lang.Iterable

forEach

Constructor Detail

MPSCQueue

public MPSCQueue(Thread consumerThread,
                 IdleStrategy idleStrategy)

Creates a new MPSCQueue with the provided IdleStrategy and consumer thread.

Parameters:

consumerThread - the Thread that consumes the items.

idleStrategy - the idleStrategy. If null, this consumer will block if the queue is empty.

Throws:

NullPointerException - when consumerThread is null.

MPSCQueue

public MPSCQueue(IdleStrategy idleStrategy)

Creates a new MPSCQueue with the provided IdleStrategy.

Parameters:

idleStrategy - the idleStrategy. If null, the consumer will block.

Method Detail

setConsumerThread

public void setConsumerThread(Thread consumerThread)

Sets the consumer thread. The consumer thread is needed for blocking, so that an offering known which thread to wakeup. There can only be a single consumerThread and this method should be called before the queue is safely published. It will not provide a happens before relation on its own.

Parameters:

consumerThread - the consumer thread.

Throws:

NullPointerException - when consumerThread null.

clear

public void clear()

. This call is threadsafe; but it will only remove the items that are on the put-stack.

Specified by:

clear in interface Collection<E>

Overrides:

clear in class AbstractQueue<E>

offer

public boolean offer(E item)

Specified by:

offer in interface BlockingQueue<E>

Specified by:

offer in interface Queue<E>

peek

public E peek()

Specified by:

peek in interface Queue<E>

take

public E take()
       throws InterruptedException

Specified by:

take in interface BlockingQueue<E>

Throws:

InterruptedException

poll

public E poll()

Specified by:

poll in interface Queue<E>

size

public int size()

. Best effort implementation.

Specified by:

size in interface Collection<E>

Specified by:

size in class AbstractCollection<E>

isEmpty

public boolean isEmpty()

Specified by:

isEmpty in interface Collection<E>

Overrides:

isEmpty in class AbstractCollection<E>

put

public void put(E e)
         throws InterruptedException

Specified by:

put in interface BlockingQueue<E>

Throws:

InterruptedException

offer

public boolean offer(E e,
                     long timeout,
                     TimeUnit unit)
              throws InterruptedException

Specified by:

offer in interface BlockingQueue<E>

Throws:

InterruptedException

poll

public E poll(long timeout,
              TimeUnit unit)
       throws InterruptedException

Specified by:

poll in interface BlockingQueue<E>

Throws:

InterruptedException

remainingCapacity

public int remainingCapacity()

Specified by:

remainingCapacity in interface BlockingQueue<E>

drainTo

public int drainTo(Collection<? super E> c)

Specified by:

drainTo in interface BlockingQueue<E>

drainTo

public int drainTo(Collection<? super E> c,
                   int maxElements)

Specified by:

drainTo in interface BlockingQueue<E>

iterator

public Iterator<E> iterator()

Specified by:

iterator in interface Iterable<E>

Specified by:

iterator in interface Collection<E>

Specified by:

iterator in class AbstractCollection<E>