Package com.inductiveautomation.perspective.gateway.threading

Class BlockingTaskQueue

java.lang.Object

com.inductiveautomation.perspective.gateway.threading.BlockingTaskQueue

public class BlockingTaskQueue
extends Object

Helps to manage threading for a series of tasks. These tasks are blocking tasks that may produce a value (T) and ideally can gracefully handle being cancelled.

This class will guarantee:

1. Only one task executes at a time.
2. All tasks execute on the executor given.
3. Tasks will have their BlockingCancelableTask.cancel() called if they exceed the configured timeout, and their completion stage will be completed exceptionally with a TaskTimedOutException
4. Tasks submitted while other tasks are executing are put into a queue. If the queue fills up, the oldest tasks are rejected first. Rejected tasks will have their completion stages completed exceptionally with a QueueOverflowException

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	BlockingTaskQueue.Builder
static enum	BlockingTaskQueue.ShutdownBehavior

Method Summary

Modifier and Type	Method	Description
static BlockingTaskQueue.Builder	newBuilder()	Create a new blocking task queue builder with a default of 30 second timeout and max queue length of 5
void	shutdown()	Shuts down the queue.
<T> CompletionStage<T>	submit(BlockingCancelableTask<T> work)	Submit a task to the queue.

Methods inherited from class java.lang.Object

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

Method Details

submit

public <T> CompletionStage<T> submit(BlockingCancelableTask<T> work)

Submit a task to the queue.

Returns:

CompletionStage that will be completed with the return value of type T produced by the task, or completed exceptionally if the task times out, the task is kicked out of the queue by more tasks, or the task throws an exception during execution.

Throws:

QueueShutdownException - if this queue has been shutdown.

shutdown

public void shutdown()

Shuts down the queue. Any excuting or pending tasks will be canceled, their completion stages completed exceptionally with a QueueShutdownException.

newBuilder

public static BlockingTaskQueue.Builder newBuilder()

Create a new blocking task queue builder with a default of 30 second timeout and max queue length of 5