Executor ensuring that all Runnables submitted are executed in order, using the provided Executor, and sequentially such that no two will ever be running at the same time.

Tasks submitted to execute(Runnable) are executed in FIFO order.

The execution of tasks is done by one thread as long as there are tasks left in the queue. When a task is interrupted, execution of subsequent tasks continues. See QueueWorker#workOnQueue for details.

RuntimeExceptions thrown by tasks are simply logged and the executor keeps trucking. If an Error is thrown, the error will propagate and execution will stop until it is restarted by a call to execute.

Nested and Inner Type Summary

Modifier and Type	Class and Description
private class	SequentialExecutor.QueueWorker Worker that runs tasks from `queue` until it is empty.
pack-priv static enum	SequentialExecutor.WorkerRunningState

Field Summary

Modifier and Type	Field and Description
private final Executor	executor Underlying executor that all submitted Runnable objects are run on.
private static final LazyLogger	log
private final Deque<Runnable>	queue
private final SequentialExecutor.QueueWorker	worker
private long	workerRunCount This counter prevents an ABA issue where a thread may successfully schedule the worker, the worker runs and exhausts the queue, another thread enqueues a task and fails to schedule the worker, and then the first thread's call to delegate.execute() returns.
private SequentialExecutor.WorkerRunningState	workerRunningState see `WorkerRunningState`

Access	Constructor and Description
pack-priv	SequentialExecutor(Executor executor) Use `MoreExecutors#newSequentialExecutor`

Modifier and Type	Method and Description
public void	execute(Runnable the runnable task task) Implements java.util.concurrent.Executor.execute. Adds a task to the queue and makes sure a worker thread is running.
public String	toString() Overrides java.lang.Object.toString. Returns a string representation of the object.

Field Detail

executor	back to summary
private final Executor executor Underlying executor that all submitted Runnable objects are run on.

log	back to summary
private static final LazyLogger log

queue	back to summary
private final Deque<Runnable> queue Annotations @GuardedBy:queue

worker	back to summary
private final SequentialExecutor.QueueWorker worker Annotations @RetainedWith

workerRunCount	back to summary
private long workerRunCount This counter prevents an ABA issue where a thread may successfully schedule the worker, the worker runs and exhausts the queue, another thread enqueues a task and fails to schedule the worker, and then the first thread's call to delegate.execute() returns. Without this counter, it would observe the QUEUING state and set it to QUEUED, and the worker would never be scheduled again for future submissions. Annotations @GuardedBy:queue

workerRunCount

back to summary

private long workerRunCount

This counter prevents an ABA issue where a thread may successfully schedule the worker, the worker runs and exhausts the queue, another thread enqueues a task and fails to schedule the worker, and then the first thread's call to delegate.execute() returns. Without this counter, it would observe the QUEUING state and set it to QUEUED, and the worker would never be scheduled again for future submissions.

Annotations

@GuardedBy:queue

workerRunningState	back to summary
private SequentialExecutor.WorkerRunningState workerRunningState see `WorkerRunningState` Annotations @LazyInit @GuardedBy:queue

SequentialExecutor	back to summary
pack-priv SequentialExecutor(Executor executor) Use `MoreExecutors#newSequentialExecutor`

Method Detail

execute back to summary

execute	back to summary
public void execute(Runnable task) Implements java.util.concurrent.Executor.execute. Adds a task to the queue and makes sure a worker thread is running. If this method throws, e.g. a `RejectedExecutionException` from the delegate executor, execution of tasks will stop until a call to this method is made. Parameters task:Runnable Doc from java.util.concurrent.Executor.execute. the runnable task Annotations @Override

public void execute(Runnable task)

Implements java.util.concurrent.Executor.execute.

Adds a task to the queue and makes sure a worker thread is running.

If this method throws, e.g. a RejectedExecutionException from the delegate executor, execution of tasks will stop until a call to this method is made.

Parameters

task:Runnable

Doc from java.util.concurrent.Executor.execute.

the runnable task

Annotations

@Override

toString	back to summary
public String toString() Overrides java.lang.Object.toString. Doc from java.lang.Object.toString. Returns a string representation of the object. Returns:String a string representation of the object Annotations @Override

toString

back to summary

public String toString()

Overrides java.lang.Object.toString.

Doc from java.lang.Object.toString.

Returns a string representation of the object.

Returns:String

a string representation of the object

Annotations

@Override

com.google.common.util.concurrent back to summary

private final Class SequentialExecutor.QueueWorker

Class Inheritance

extends Object
implements Runnable

java.lang.Object
com.google.common.util.concurrent.SequentialExecutor.QueueWorker

All Implemented Interfaces

java.lang.Runnable

Worker that runs tasks from queue until it is empty.

Field Summary

Modifier and Type	Field and Description
pack-priv Runnable	task

Constructor Summary

Access	Constructor and Description
private	QueueWorker()

Method Summary

Modifier and Type	Method and Description
public void	run() Implements java.lang.Runnable.run. Runs this operation.
public String	toString() Overrides java.lang.Object.toString. Returns a string representation of the object.
private void	workOnQueue() Continues executing tasks from `queue` until it is empty.

Inherited from java.lang.Object:: clone equals finalize getClass hashCode notify notifyAll wait wait wait

Field Detail

task	back to summary
pack-priv Runnable task Annotations @CheckForNull

Constructor Detail

QueueWorker	back to summary
private QueueWorker()

Method Detail

run	back to summary
public void run() Implements java.lang.Runnable.run. Doc from java.lang.Runnable.run. Runs this operation. Annotations @Override

run

back to summary

public void run()

Implements java.lang.Runnable.run.

Doc from java.lang.Runnable.run.

Runs this operation.

Annotations

@Override

toString	back to summary
public String toString() Overrides java.lang.Object.toString. Doc from java.lang.Object.toString. Returns a string representation of the object. Returns:String a string representation of the object Annotations @SuppressWarnings:GuardedBy @Override

toString

back to summary

public String toString()

Overrides java.lang.Object.toString.

Doc from java.lang.Object.toString.

Returns a string representation of the object.

Returns:String

a string representation of the object

Annotations

@SuppressWarnings:GuardedBy
@Override

workOnQueue back to summary

workOnQueue	back to summary
private void workOnQueue() Continues executing tasks from `queue` until it is empty. The thread's interrupt bit is cleared before execution of each task. If the Thread in use is interrupted before or during execution of the tasks in `queue`, the Executor will complete its tasks, and then restore the interruption. This means that once the Thread returns to the Executor that this Executor composes, the interruption will still be present. If the composed Executor is an ExecutorService, it can respond to shutdown() by returning tasks queued on that Thread after `worker` drains the queue. Annotations @SuppressWarnings:CatchingUnchecked

private void workOnQueue()

Continues executing tasks from queue until it is empty.

The thread's interrupt bit is cleared before execution of each task.

If the Thread in use is interrupted before or during execution of the tasks in queue, the Executor will complete its tasks, and then restore the interruption. This means that once the Thread returns to the Executor that this Executor composes, the interruption will still be present. If the composed Executor is an ExecutorService, it can respond to shutdown() by returning tasks queued on that Thread after worker drains the queue.

Annotations

@SuppressWarnings:CatchingUnchecked

com.google.common.util.concurrent back to summary

pack-priv final Enum SequentialExecutor.WorkerRunningState

Class Inheritance

extends Enum<SequentialExecutor.WorkerRunningState>

java.lang.Object
java.lang.Enum
com.google.common.util.concurrent.SequentialExecutor.WorkerRunningState

Field Summary

Modifier and Type	Field and Description
public static final SequentialExecutor.WorkerRunningState	IDLE Runnable is not running and not queued for execution
public static final SequentialExecutor.WorkerRunningState	QUEUED runnable has been submitted but has not yet begun execution
public static final SequentialExecutor.WorkerRunningState	QUEUING Runnable is not running, but is being queued for execution
public static final SequentialExecutor.WorkerRunningState	RUNNING

Constructor Summary

Access	Constructor and Description
private	WorkerRunningState()

Method Summary

Modifier and Type	Method and Description
public static SequentialExecutor.WorkerRunningState	valueOf(String name)
public static SequentialExecutor.WorkerRunningState[]	values()

Inherited from java.lang.Enum:: clone compareTo describeConstable equals finalize getDeclaringClass hashCode name ordinal toString valueOf

Field Detail

IDLE	back to summary
public static final SequentialExecutor.WorkerRunningState IDLE Runnable is not running and not queued for execution

QUEUED	back to summary
public static final SequentialExecutor.WorkerRunningState QUEUED runnable has been submitted but has not yet begun execution

QUEUING	back to summary
public static final SequentialExecutor.WorkerRunningState QUEUING Runnable is not running, but is being queued for execution

RUNNING	back to summary
public static final SequentialExecutor.WorkerRunningState RUNNING

Constructor Detail

WorkerRunningState	back to summary
private WorkerRunningState()

Method Detail

valueOf	back to summary
public static SequentialExecutor.WorkerRunningState valueOf(String name)

values	back to summary
public static SequentialExecutor.WorkerRunningState[] values()

pack-priv final Class SequentialExecutor

Nested and Inner Type Summary

Field Summary

Constructor Summary

Method Summary

Field Detail

Constructor Detail

Method Detail

private final Class SequentialExecutor.QueueWorker

Field Summary

Constructor Summary

Method Summary

Field Detail

Constructor Detail

Method Detail

pack-priv final Enum SequentialExecutor.WorkerRunningState

Field Summary

Constructor Summary

Method Summary

Field Detail

Constructor Detail

Method Detail