com.graphaware.writer.service

Class QueueBackedScheduledService<E>

java.lang.Object

com.google.common.util.concurrent.AbstractScheduledService

com.graphaware.writer.service.QueueBackedScheduledService<E>

All Implemented Interfaces:

com.google.common.util.concurrent.Service

Direct Known Subclasses:

BaseThirdPartyWriter, SingleThreadedWriter

public abstract class QueueBackedScheduledService<E>
extends com.google.common.util.concurrent.AbstractScheduledService

A AbstractScheduledService that maintains a queue of tasks and executes them in a single thread by constantly pulling the tasks from the head of the queue.

By default, if the queue capacity is full, tasks are dropped and a warning is logged.

Note that start() must be called in order to start processing the queue and stop() should be called before the application is shut down.

Nested Class Summary

Nested classes/interfaces inherited from class com.google.common.util.concurrent.AbstractScheduledService

com.google.common.util.concurrent.AbstractScheduledService.CustomScheduler, com.google.common.util.concurrent.AbstractScheduledService.Scheduler

Nested classes/interfaces inherited from interface com.google.common.util.concurrent.Service

com.google.common.util.concurrent.Service.Listener, com.google.common.util.concurrent.Service.State

Field Summary

Fields

Modifier and Type	Field and Description
static int	DEFAULT_QUEUE_CAPACITY
protected LinkedBlockingDeque<E>	queue

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	QueueBackedScheduledService() Construct a new service with a default queue capacity of DEFAULT_QUEUE_CAPACITY.
protected	QueueBackedScheduledService(int queueCapacity) Construct a new service.

Method Summary

Modifier and Type	Method and Description
boolean	equals(Object o)
int	hashCode()
protected boolean	logEmptyQueue() Return true iff empty queue should be logged.
protected long	loggingFrequencyMs() How often in ms should the queue size be reported to the log.
protected boolean	offer(E futureTask) Offer a task to the queue for processing.
protected com.google.common.util.concurrent.AbstractScheduledService.Scheduler	scheduler()
protected void	shutDown()
void	start() Start the processing of tasks.
void	stop() Stop the processing of tasks.

Methods inherited from class com.google.common.util.concurrent.AbstractScheduledService

addListener, awaitRunning, awaitRunning, awaitTerminated, awaitTerminated, executor, failureCause, isRunning, runOneIteration, serviceName, startAsync, startUp, state, stopAsync, toString

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

DEFAULT_QUEUE_CAPACITY

public static final int DEFAULT_QUEUE_CAPACITY

See Also:

Constant Field Values

queue

protected final LinkedBlockingDeque<E> queue

Constructor Detail

QueueBackedScheduledService

protected QueueBackedScheduledService()

Construct a new service with a default queue capacity of DEFAULT_QUEUE_CAPACITY.

QueueBackedScheduledService

protected QueueBackedScheduledService(int queueCapacity)

Construct a new service.

Parameters:

queueCapacity - capacity of the queue.

Method Detail

start

public void start()

Start the processing of tasks.

stop

public void stop()

Stop the processing of tasks.

shutDown

protected void shutDown()
                 throws Exception

Overrides:

shutDown in class com.google.common.util.concurrent.AbstractScheduledService

Throws:

Exception

offer

protected boolean offer(E futureTask)

Offer a task to the queue for processing. Intended to be overridden. By default, don't wait and return false in case the queue is full, otherwise return true.

Parameters:

futureTask - to offer to the queue.

Returns:

true iff the task was accepted.

logEmptyQueue

protected boolean logEmptyQueue()

Return true iff empty queue should be logged. Defaults to false, intended to be overridden.

Returns:

true iff empty queue should be logged.

loggingFrequencyMs

protected long loggingFrequencyMs()

How often in ms should the queue size be reported to the log.

Returns:

logging interval in ms. The default is LOGGING_INTERVAL_MS, intended to be overridden.

scheduler

protected com.google.common.util.concurrent.AbstractScheduledService.Scheduler scheduler()

Specified by:

scheduler in class com.google.common.util.concurrent.AbstractScheduledService

equals

public boolean equals(Object o)

Overrides:

equals in class Object

hashCode

public int hashCode()

Overrides:

hashCode in class Object