Module org.eclipse.milo.opcua.stack.core

Package org.eclipse.milo.opcua.stack.core.util

Class TaskQueue

java.lang.Object

org.eclipse.milo.opcua.stack.core.util.TaskQueue

public final class TaskQueue
extends Object

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static final class	TaskQueue.Builder
static interface	TaskQueue.Task
static enum	TaskQueue.TaskPriority

Constructor Summary

Constructors

Constructor	Description
TaskQueue(Executor executor)	Create a TaskQueue that executes TaskQueue.Tasks on the provided Executor.
TaskQueue(Executor executor, int maxConcurrentTasks, int maxQueueSize, int priorityRatio)	Create a TaskQueue that executes TaskQueue.Tasks on the provided Executor.

Method Summary

Modifier and Type	Method	Description
boolean	execute(TaskQueue.Task task)	Queue a TaskQueue.Task to be executed.
int	getPending()	Get the current number of tasks that are pending execution.
int	getQueueSize()	Get the current number of tasks waiting in the queue.
boolean	isShutdown()
static TaskQueue.Builder	newBuilder()
void	pause()	Pause execution of queued TaskQueue.Tasks.
void	resume()	Resume execution of queued TaskQueue.Tasks.
List<TaskQueue.Task>	shutdown(boolean awaitQuiescence)	Shut down this executor, optionally awaiting completion of any currently-executing tasks.
@Nullable CompletionStage<Unit>	submit(TaskQueue.Task task)	Queue a TaskQueue.Task to be executed, returning a CompletionStage that will complete when the task has been executed.

Methods inherited from class java.lang.Object

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

Constructor Details

TaskQueue

public TaskQueue(Executor executor)

Create a TaskQueue that executes TaskQueue.Tasks on the provided Executor.

All other parameters are default values.

Parameters:

executor - the Executor that TaskQueue.Tasks will use to execute.

See Also:

• DEFAULT_MAX_CONCURRENT_TASKS
• DEFAULT_MAX_QUEUE_SIZE
• DEFAULT_PRIORITY_RATIO

TaskQueue

public TaskQueue(Executor executor,
 int maxConcurrentTasks,
 int maxQueueSize,
 int priorityRatio)

Create a TaskQueue that executes TaskQueue.Tasks on the provided Executor.

Parameters:

executor - the Executor that TaskQueue.Tasks will use to execute.

maxConcurrentTasks - the number of concurrently executing tasks allowed. When 1, the default value, submitted Tasks are guaranteed to execute serially.

maxQueueSize - the maximum number of Tasks that can be queued before backpressure is applied and execute(Task) starts returning false.

priorityRatio - ratio of TaskQueue.TaskPriority.ELEVATED tasks to TaskQueue.TaskPriority.REGULAR tasks that will be executed when elevated tasks are continually being dequeued.

Method Details

execute

public boolean execute(TaskQueue.Task task)

Queue a TaskQueue.Task to be executed.

Parameters:

task - the TaskQueue.Task to be executed.

Returns:

true if task was queued for execution, or false if it was not queued, either because this TaskQueue is shut down, or because backpressure is being applied because the configured max queue size would be exceeded.

submit

public @Nullable CompletionStage<Unit> submit(TaskQueue.Task task)

Queue a TaskQueue.Task to be executed, returning a CompletionStage that will complete when the task has been executed.

The callback completes asynchronously, using the TaskQueue's configured Executor, and does not block execution of any further queued tasks.

Parameters:

task - the TaskQueue.Task to be executed.

Returns:

a CompletionStage that will complete when task has been executed, or null if the task was not queued, either because this TaskQueue is shut down, or because backpressure is being applied because the configured max queue size would be exceeded.

pause

public void pause()

Pause execution of queued TaskQueue.Tasks.

resume

public void resume()

Resume execution of queued TaskQueue.Tasks.

shutdown

public List<TaskQueue.Task> shutdown(boolean awaitQuiescence)
                              throws InterruptedException

Shut down this executor, optionally awaiting completion of any currently-executing tasks.

Parameters:

awaitQuiescence - true if this method should block awaiting completion of any currently-executing tasks.

Returns:

a List of TaskQueue.Tasks that were queued and will not be executed.

Throws:

InterruptedException - if the current Thread is interrupted while waiting.

isShutdown

public boolean isShutdown()

getQueueSize

public int getQueueSize()

Get the current number of tasks waiting in the queue.

This count does not include tasks that are currently executing.

Returns:

the current number of tasks waiting in the queue.

getPending

public int getPending()

Get the current number of tasks that are pending execution.

Pending tasks have been dequeued and submitted to the executor but have not yet completed.

Returns:

the current number of tasks pending execution.

newBuilder

public static TaskQueue.Builder newBuilder()

Returns:

a new TaskQueue.Builder instance.