org.threadly.concurrent

Class SingleThreadScheduler

java.lang.Object

org.threadly.concurrent.AbstractSubmitterExecutor

org.threadly.concurrent.AbstractSubmitterScheduler

org.threadly.concurrent.AbstractPriorityScheduler

org.threadly.concurrent.SingleThreadScheduler

All Implemented Interfaces:

java.util.concurrent.Executor, PrioritySchedulerService, SchedulerService, SubmitterExecutor, SubmitterScheduler

Direct Known Subclasses:

SingleThreadSchedulerStatisticTracker

public class SingleThreadScheduler
extends AbstractPriorityScheduler

A simple and light weight implementation of the SchedulerService. This is designed to be a lighter weight option to the PriorityScheduler, for when multiple threads are either not needed, or not desired.

Since:

2.0.0

Constructor Summary

Constructors

Constructor and Description
SingleThreadScheduler() Constructs a new SingleThreadScheduler.
SingleThreadScheduler(boolean daemonThread) Constructs a new SingleThreadScheduler.
SingleThreadScheduler(TaskPriority defaultPriority, long maxWaitForLowPriorityInMs) Constructs a new SingleThreadScheduler.
SingleThreadScheduler(TaskPriority defaultPriority, long maxWaitForLowPriorityInMs, boolean daemonThread) Constructs a new SingleThreadScheduler.
SingleThreadScheduler(TaskPriority defaultPriority, long maxWaitForLowPriorityInMs, java.util.concurrent.ThreadFactory threadFactory) Constructs a new SingleThreadScheduler.
SingleThreadScheduler(java.util.concurrent.ThreadFactory threadFactory) Constructs a new SingleThreadScheduler.

Method Summary

Modifier and Type	Method and Description
void	awaitTermination() Block until the thread pool has shutdown and all threads have been stopped.
boolean	awaitTermination(long timeoutMillis) Block until the thread pool has shutdown and all threads have been stopped.
int	getActiveTaskCount() Call to check how many tasks are currently being executed in this scheduler.
boolean	isShutdown() Function to check if the thread pool is currently accepting and handling tasks.
boolean	isTerminated() One step beyond isShutdown(), a true here indicates that not only has a shutdown on the pool been requested, but that the thread running tasks has completed.
void	prestartExecutionThread() Start thread for execution if not already started.
void	prestartExecutionThread(boolean blockTillStarted) Start thread for execution if not already started.
void	scheduleAtFixedRate(java.lang.Runnable task, long initialDelay, long period, TaskPriority priority) Schedule a fixed rate recurring task to run.
void	scheduleWithFixedDelay(java.lang.Runnable task, long initialDelay, long recurringDelay, TaskPriority priority) Schedule a fixed delay recurring task to run.
void	shutdown() Stops any new tasks from being submitted to the pool.
java.util.List<java.lang.Runnable>	shutdownNow() Stops any new tasks from being submitted to the pool.

Methods inherited from class org.threadly.concurrent.AbstractPriorityScheduler

execute, getDefaultPriority, getMaxWaitForLowPriority, getQueuedTaskCount, getQueuedTaskCount, getWaitingForExecutionTaskCount, getWaitingForExecutionTaskCount, remove, remove, schedule, scheduleAtFixedRate, scheduleWithFixedDelay, setMaxWaitForLowPriority, submit, submit, submitScheduled, submitScheduled

Methods inherited from class org.threadly.concurrent.AbstractSubmitterScheduler

schedule, submitScheduled, submitScheduled

Methods inherited from class org.threadly.concurrent.AbstractSubmitterExecutor

execute, submit, submit

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.threadly.concurrent.PrioritySchedulerService

submit, submitScheduled

Methods inherited from interface org.threadly.concurrent.SubmitterScheduler

schedule, submitScheduled, submitScheduled, submitScheduled

Methods inherited from interface org.threadly.concurrent.SubmitterExecutor

submit, submit, submit

Methods inherited from interface java.util.concurrent.Executor

execute

Constructor Detail

SingleThreadScheduler

public SingleThreadScheduler()

Constructs a new SingleThreadScheduler. No threads will start until the first task is provided. This defaults to using a daemon thread for the scheduler.

SingleThreadScheduler

public SingleThreadScheduler(TaskPriority defaultPriority,
                             long maxWaitForLowPriorityInMs)

Constructs a new SingleThreadScheduler. No threads will start until the first task is provided. This defaults to using a daemon thread for the scheduler.

Parameters:

defaultPriority - Default priority for tasks which are submitted without any specified priority

maxWaitForLowPriorityInMs - time low priority tasks to wait if there are high priority tasks ready to run

SingleThreadScheduler

public SingleThreadScheduler(boolean daemonThread)

Constructs a new SingleThreadScheduler. No threads will start until the first task is provided.

Parameters:

daemonThread - true if scheduler thread should be a daemon thread

SingleThreadScheduler

public SingleThreadScheduler(TaskPriority defaultPriority,
                             long maxWaitForLowPriorityInMs,
                             boolean daemonThread)

Constructs a new SingleThreadScheduler. No threads will start until the first task is provided.

Parameters:

defaultPriority - Default priority for tasks which are submitted without any specified priority

maxWaitForLowPriorityInMs - time low priority tasks to wait if there are high priority tasks ready to run

daemonThread - true if scheduler thread should be a daemon thread

SingleThreadScheduler

public SingleThreadScheduler(java.util.concurrent.ThreadFactory threadFactory)

Constructs a new SingleThreadScheduler. No threads will start until the first task is provided.

Parameters:

threadFactory - factory to make thread for scheduler

SingleThreadScheduler

public SingleThreadScheduler(TaskPriority defaultPriority,
                             long maxWaitForLowPriorityInMs,
                             java.util.concurrent.ThreadFactory threadFactory)

Constructs a new SingleThreadScheduler. No threads will start until the first task is provided.

Parameters:

defaultPriority - Default priority for tasks which are submitted without any specified priority

maxWaitForLowPriorityInMs - time low priority tasks to wait if there are high priority tasks ready to run

threadFactory - factory to make thread for scheduler

Method Detail

shutdown

public void shutdown()

Stops any new tasks from being submitted to the pool. But allows all tasks which are submitted to execute, or scheduled (and have elapsed their delay time) to run. If recurring tasks are present they will also be unable to reschedule. This call will not block to wait for the shutdown of the scheduler to finish. If shutdown() or shutdownNow() has already been called, this will have no effect.

If you wish to not want to run any queued tasks you should use shutdownNow().

shutdownNow

public java.util.List<java.lang.Runnable> shutdownNow()

Stops any new tasks from being submitted to the pool. If any tasks are waiting for execution they will be prevented from being run. If a task is currently running it will be allowed to finish (though this call will not block waiting for it to finish).

Returns:

returns a list of runnables which were waiting in the queue to be run at time of shutdown

awaitTermination

public void awaitTermination()
                      throws java.lang.InterruptedException

Block until the thread pool has shutdown and all threads have been stopped. If neither shutdown() or shutdownNow() is invoked, then this will block forever.

Throws:

java.lang.InterruptedException - Thrown if blocking thread is interrupted waiting for shutdown

awaitTermination

public boolean awaitTermination(long timeoutMillis)
                         throws java.lang.InterruptedException

Block until the thread pool has shutdown and all threads have been stopped. If neither shutdown() or shutdownNow() is invoked, then this will block until the timeout is reached.

Parameters:

timeoutMillis - time to block and wait for thread pool to shutdown

Returns:

true if the pool has shutdown, false if timeout was reached

Throws:

java.lang.InterruptedException - Thrown if blocking thread is interrupted waiting for shutdown

isShutdown

public boolean isShutdown()

Description copied from interface: SchedulerService

Function to check if the thread pool is currently accepting and handling tasks.

Returns:

true if thread pool is running

isTerminated

public boolean isTerminated()

One step beyond isShutdown(), a true here indicates that not only has a shutdown on the pool been requested, but that the thread running tasks has completed.

Returns:

true if this scheduler is no longer processing any tasks

prestartExecutionThread

public void prestartExecutionThread()

Start thread for execution if not already started. This can avoid the minor delay of the thread starting later. This will not block till the thread is running, instead letting it start in the background (usually fine).

prestartExecutionThread

public void prestartExecutionThread(boolean blockTillStarted)

Start thread for execution if not already started. This can avoid the minor delay of the thread starting later.

Parameters:

blockTillStarted - If true this will not return till the scheduler thread has started

scheduleWithFixedDelay

public void scheduleWithFixedDelay(java.lang.Runnable task,
                                   long initialDelay,
                                   long recurringDelay,
                                   TaskPriority priority)

Description copied from interface: PrioritySchedulerService

Schedule a fixed delay recurring task to run. The recurring delay time will be from the point where execution has finished. So the execution frequency is the recurringDelay + runtime for the provided task.

Unlike ScheduledExecutorService if the task throws an exception, subsequent executions are NOT suppressed or prevented. So if the task throws an exception on every run, the task will continue to be executed at the provided recurring delay (possibly throwing an exception on each execution).

Parameters:

task - runnable to be executed

initialDelay - delay in milliseconds until first run

recurringDelay - delay in milliseconds for running task after last finish

priority - priority for task to get available thread to run on

scheduleAtFixedRate

public void scheduleAtFixedRate(java.lang.Runnable task,
                                long initialDelay,
                                long period,
                                TaskPriority priority)

Description copied from interface: PrioritySchedulerService

Schedule a fixed rate recurring task to run. The recurring delay will be the same, regardless of how long task execution takes. A given runnable will not run concurrently (unless it is submitted to the scheduler multiple times). Instead of execution takes longer than the period, the next run will occur immediately (given thread availability in the pool).

Unlike ScheduledExecutorService if the task throws an exception, subsequent executions are NOT suppressed or prevented. So if the task throws an exception on every run, the task will continue to be executed at the provided recurring delay (possibly throwing an exception on each execution).

Parameters:

task - runnable to be executed

initialDelay - delay in milliseconds until first run

period - amount of time in milliseconds between the start of recurring executions

priority - priority for task to get available thread to run on

getActiveTaskCount

public int getActiveTaskCount()

Description copied from interface: SchedulerService

Call to check how many tasks are currently being executed in this scheduler.

Returns:

current number of running tasks