Package org.openstreetmap.josm.data.cache

Class HostLimitQueue

java.lang.Object

java.util.AbstractCollection<E>

java.util.AbstractQueue<E>

java.util.concurrent.LinkedBlockingDeque<java.lang.Runnable>

org.openstreetmap.josm.data.cache.HostLimitQueue

All Implemented Interfaces:

java.io.Serializable, java.lang.Iterable<java.lang.Runnable>, java.util.Collection<java.lang.Runnable>, java.util.concurrent.BlockingDeque<java.lang.Runnable>, java.util.concurrent.BlockingQueue<java.lang.Runnable>, java.util.Deque<java.lang.Runnable>, java.util.Queue<java.lang.Runnable>

public class HostLimitQueue
extends java.util.concurrent.LinkedBlockingDeque<java.lang.Runnable>

Queue for ThreadPoolExecutor that implements per-host limit. It will acquire a semaphore for each task and it will set a runnable task with semaphore release, when job has finished.

This implementation doesn't guarantee to have at most hostLimit connections per host[1], and it doesn't guarantee that all threads will be busy, when there is work for them[2].
[1] More connection per host may happen, when ThreadPoolExecutor is growing its pool, and thus tasks do not go through the Queue
[2] If we have a queue, and for all hosts in queue we will fail to acquire semaphore, the thread take the first available job and wait for semaphore. It might be the case, that semaphore was released for some task further in queue, but this implementation doesn't try to detect such situation

See Also:

Serialized Form

Field Summary

Fields

Modifier and Type	Field	Description
private int	hostLimit
private java.util.Map<java.lang.String,java.util.concurrent.Semaphore>	hostSemaphores
private static long	serialVersionUID

Constructor Summary

Constructors

Constructor	Description
HostLimitQueue(int hostLimit)	Creates an unbounded queue
HostLimitQueue(int hostLimit, int queueLimit)	Creates bounded queue

Method Summary

Modifier and Type	Method	Description
private void	acquireSemaphore(java.lang.Runnable job)
private JCSCachedTileLoaderJob<?,?>	findJob()
private java.util.concurrent.Semaphore	getSemaphore(JCSCachedTileLoaderJob<?,?> job)
java.lang.Runnable	poll(long timeout, java.util.concurrent.TimeUnit unit)
private void	releaseSemaphore(JCSCachedTileLoaderJob<?,?> job)
java.lang.Runnable	take()
private boolean	tryAcquireSemaphore(java.lang.Runnable job, long timeout, java.util.concurrent.TimeUnit unit)
private boolean	tryAcquireSemaphore(JCSCachedTileLoaderJob<?,?> job)

Methods inherited from class java.util.concurrent.LinkedBlockingDeque

add, addAll, addFirst, addLast, clear, contains, descendingIterator, drainTo, drainTo, element, forEach, getFirst, getLast, iterator, offer, offer, offerFirst, offerFirst, offerLast, offerLast, peek, peekFirst, peekLast, poll, pollFirst, pollFirst, pollLast, pollLast, pop, push, put, putFirst, putLast, remainingCapacity, remove, remove, removeAll, removeFirst, removeFirstOccurrence, removeIf, removeLast, removeLastOccurrence, retainAll, size, spliterator, takeFirst, takeLast, toArray, toArray, toString

Methods inherited from class java.util.AbstractCollection

containsAll, isEmpty

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.util.Collection

containsAll, equals, hashCode, isEmpty, parallelStream, stream, toArray

Field Detail

serialVersionUID

private static final long serialVersionUID

See Also:

Constant Field Values

hostSemaphores

private final java.util.Map<java.lang.String,java.util.concurrent.Semaphore> hostSemaphores

hostLimit

private final int hostLimit

Constructor Detail

HostLimitQueue

public HostLimitQueue(int hostLimit)

Creates an unbounded queue

Parameters:

hostLimit - how many parallel calls to host to allow

HostLimitQueue

public HostLimitQueue(int hostLimit,
                      int queueLimit)

Creates bounded queue

Parameters:

hostLimit - how many parallel calls to host to allow

queueLimit - how deep the queue should be

Method Detail

findJob

private JCSCachedTileLoaderJob<?,?> findJob()

poll

public java.lang.Runnable poll(long timeout,
                               java.util.concurrent.TimeUnit unit)
                        throws java.lang.InterruptedException

Specified by:

poll in interface java.util.concurrent.BlockingDeque<java.lang.Runnable>

Specified by:

poll in interface java.util.concurrent.BlockingQueue<java.lang.Runnable>

Overrides:

poll in class java.util.concurrent.LinkedBlockingDeque<java.lang.Runnable>

Throws:

java.lang.InterruptedException

take

public java.lang.Runnable take()
                        throws java.lang.InterruptedException

Specified by:

take in interface java.util.concurrent.BlockingDeque<java.lang.Runnable>

Specified by:

take in interface java.util.concurrent.BlockingQueue<java.lang.Runnable>

Overrides:

take in class java.util.concurrent.LinkedBlockingDeque<java.lang.Runnable>

Throws:

java.lang.InterruptedException

getSemaphore

private java.util.concurrent.Semaphore getSemaphore(JCSCachedTileLoaderJob<?,?> job)

acquireSemaphore

private void acquireSemaphore(java.lang.Runnable job)
                       throws java.lang.InterruptedException

Throws:

java.lang.InterruptedException

tryAcquireSemaphore

private boolean tryAcquireSemaphore(JCSCachedTileLoaderJob<?,?> job)

tryAcquireSemaphore

private boolean tryAcquireSemaphore(java.lang.Runnable job,
                                    long timeout,
                                    java.util.concurrent.TimeUnit unit)
                             throws java.lang.InterruptedException

Throws:

java.lang.InterruptedException

releaseSemaphore

private void releaseSemaphore(JCSCachedTileLoaderJob<?,?> job)