Class TaskQueue

java.lang.Object

java.util.AbstractCollection<Runnable>

java.util.AbstractQueue<Runnable>

java.util.concurrent.LinkedBlockingQueue<Runnable>

org.apache.tomcat.util.threads.TaskQueue

All Implemented Interfaces:

Serializable, Iterable<Runnable>, Collection<Runnable>, BlockingQueue<Runnable>, Queue<Runnable>, RetryableQueue<Runnable>

public class TaskQueue
extends LinkedBlockingQueue<Runnable>
implements RetryableQueue<Runnable>

A task queue specifically designed to run with a thread pool executor. The task queue is optimised to properly utilize threads within a thread pool executor. A normal queue causes the executor to queue tasks first and only create new threads once the queue is full. This queue instead refuses to queue a task while all existing threads are busy and the pool size is below its maximum, so the executor creates a new thread for the task instead. It also supports forcing items onto the queue via force(Runnable).

See Also:

• Serialized Form

Field Summary

Fields

Modifier and Type	Field	Description
protected static final StringManager	sm	The string manager for this package.

Constructor Summary

Constructors

Constructor	Description
TaskQueue()	Constructs a new TaskQueue with default capacity.
TaskQueue(int capacity)	Constructs a new TaskQueue with the given capacity.
TaskQueue(Collection<? extends Runnable> c)	Constructs a new TaskQueue containing the elements in the given collection.

Method Summary

Modifier and Type	Method	Description
boolean	force(Runnable o)	Used to add a task to the queue if the task has been rejected by the Executor.
boolean	force(Runnable o, long timeout, TimeUnit unit)	Deprecated.
boolean	offer(Runnable o)
Runnable	poll(long timeout, TimeUnit unit)	Removes and returns the head of this queue, waiting up to the specified wait time if necessary for an element to become available.
void	setParent(ThreadPoolExecutor tp)	Sets the parent thread pool executor for this queue.
Runnable	take()

Methods inherited from class LinkedBlockingQueue

clear, contains, drainTo, drainTo, forEach, iterator, offer, peek, poll, put, remainingCapacity, remove, removeAll, removeIf, retainAll, size, spliterator, toArray, toArray, toString

Methods inherited from class AbstractQueue

add, addAll, element, remove

Methods inherited from class AbstractCollection

containsAll, isEmpty

Methods inherited from class Object

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

Methods inherited from interface BlockingQueue

add, contains, drainTo, drainTo, offer, put, remainingCapacity, remove

Methods inherited from interface Collection

addAll, clear, containsAll, equals, hashCode, isEmpty, iterator, parallelStream, removeAll, removeIf, retainAll, size, spliterator, stream, toArray, toArray, toArray

Methods inherited from interface Iterable

forEach

Methods inherited from interface Queue

element, peek, poll, remove

Field Details

sm

protected static final StringManager sm

The string manager for this package.

Constructor Details

TaskQueue

public TaskQueue()

Constructs a new TaskQueue with default capacity.

TaskQueue

public TaskQueue(int capacity)

Constructs a new TaskQueue with the given capacity.

Parameters:

capacity - the queue capacity

TaskQueue

public TaskQueue(Collection<? extends Runnable> c)

Constructs a new TaskQueue containing the elements in the given collection.

Parameters:

c - the collection of initial elements

Method Details

setParent

public void setParent(ThreadPoolExecutor tp)

Sets the parent thread pool executor for this queue.

Parameters:

tp - the parent executor

force

public boolean force(Runnable o)

Description copied from interface: RetryableQueue

Used to add a task to the queue if the task has been rejected by the Executor.

Specified by:

force in interface RetryableQueue<Runnable>

Parameters:

o - The task to add to the queue

Returns:

true if the task was added to the queue, otherwise false

force

@Deprecated
public boolean force(Runnable o,
 long timeout,
 TimeUnit unit)
              throws InterruptedException

Deprecated.

Description copied from interface: RetryableQueue

Used to add a task to the queue if the task has been rejected by the Executor.

Specified by:

force in interface RetryableQueue<Runnable>

Parameters:

o - The task to add to the queue

timeout - The timeout to use when adding the task

unit - The units in which the timeout is expressed

Returns:

true if the task was added to the queue, otherwise false

Throws:

InterruptedException - If the call is interrupted before the timeout expires

offer

public boolean offer(Runnable o)

Specified by:

offer in interface BlockingQueue<Runnable>

Specified by:

offer in interface Queue<Runnable>

Overrides:

offer in class LinkedBlockingQueue<Runnable>

poll

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

Removes and returns the head of this queue, waiting up to the specified wait time if necessary for an element to become available.

Specified by:

poll in interface BlockingQueue<Runnable>

Overrides:

poll in class LinkedBlockingQueue<Runnable>

Parameters:

timeout - the maximum time to wait

unit - the time unit of the timeout argument

Returns:

the head of this queue, or null if the specified waiting time elapses before an element becomes available

Throws:

InterruptedException - if interrupted while waiting

StopPooledThreadException - if the current thread is due to be stopped by the parent executor

take

public Runnable take()
              throws InterruptedException

Specified by:

take in interface BlockingQueue<Runnable>

Overrides:

take in class LinkedBlockingQueue<Runnable>

Throws:

InterruptedException