org.opennms.netmgt.linkd.scheduler

Class Scheduler

java.lang.Object

org.opennms.netmgt.linkd.scheduler.Scheduler

All Implemented Interfaces:

Runnable, Fiber, PausableFiber, ScheduleTimer, Timer

public class Scheduler
extends Object
implements Runnable, PausableFiber, ScheduleTimer

This class implements a simple scheduler to ensure the polling occurs at the expected intervals. The scheduler employees a dynamic thread pool that adjust to the load until a maximum thread count is reached.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	Scheduler.PeekableFifoQueue<T> This queue extends the standard FIFO queue instance so that it is possible to peek at an instance without removing it from the queue.

Field Summary

Fields

Modifier and Type	Field and Description
Map<Long,Scheduler.PeekableFifoQueue<ReadyRunnable>>	m_queues The map of queue that contain ready runnable instances.
ExecutorService	m_runner The pool of threads that are used to executed the runnable instances scheduled by the class' instance.
int	m_scheduled The total number of elements currently scheduled.
int	m_status The status for this fiber.

Fields inherited from interface org.opennms.core.fiber.PausableFiber

PAUSE_PENDING, PAUSED, RESUME_PENDING

Fields inherited from interface org.opennms.core.fiber.Fiber

RUNNING, START_PENDING, STARTING, STATUS_NAMES, STOP_PENDING, STOPPED

Constructor Summary

Constructors

Constructor and Description
Scheduler(String parent, int maxSize) Constructs a new instance of the scheduler.
Scheduler(String parent, int maxSize, float lowMark, float hiMark) Constructs a new instance of the scheduler.

Method Summary

Methods

Modifier and Type	Method and Description
long	getCurrentTime() This returns the current time for the scheduler
String	getName() Returns the name of this fiber.
ReadyRunnable	getReadyRunnable(ReadyRunnable runnable) This method is used to get a ready runnable in the system.
ReadyRunnable	getReadyRunnable(ReadyRunnable runnable, long interval) getReadyRunnable
int	getStatus() Returns the current of this fiber.
void	pause() Pauses the scheduler if it is current running.
void	resume() Resumes the scheduler if it has been paused.
void	run() The main method of the scheduler.
void	schedule(long interval, ReadyRunnable runnable) schedule
void	schedule(ReadyRunnable runnable, long interval) This method is used to schedule a ready runnable in the system.
void	start() Starts the fiber.
void	stop() Stops the fiber.
void	unschedule(ReadyRunnable runnable) This method is used to unschedule a ready runnable in the system.
void	unschedule(ReadyRunnable runnable, long interval) This method is used to unschedule a ready runnable in the system.

Methods inherited from class java.lang.Object

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

Field Detail

m_queues

public Map<Long,Scheduler.PeekableFifoQueue<ReadyRunnable>> m_queues

The map of queue that contain ready runnable instances. The queues are mapped according to the interval of scheduling.

m_scheduled

public int m_scheduled

The total number of elements currently scheduled. This should be the sum of all the elements in the various queues.

m_runner

public ExecutorService m_runner

The pool of threads that are used to executed the runnable instances scheduled by the class' instance.

m_status

public int m_status

The status for this fiber.

Constructor Detail

Scheduler

public Scheduler(String parent,
         int maxSize)

Constructs a new instance of the scheduler. The maximum number of executable threads is specified in the constructor. The executable threads are part of a runnable thread pool where the scheduled runnables are executed.

Parameters:

parent - String prepended to "Scheduler" to create fiber name

maxSize - The maximum size of the thread pool.

Scheduler

public Scheduler(String parent,
         int maxSize,
         float lowMark,
         float hiMark)

Constructs a new instance of the scheduler. The maximum number of executable threads is specified in the constructor. The executable threads are part of a runnable thread pool where the scheduled runnables are executed.

Parameters:

parent - String prepended to "Scheduler" to create fiber name

maxSize - The maximum size of the thread pool.

lowMark - The low water mark ratios of thread size to threads when threads are stopped.

hiMark - The high water mark ratio of thread size to threads when threads are started.

Method Detail

schedule

public void schedule(ReadyRunnable runnable,
            long interval)

This method is used to schedule a ready runnable in the system. The interval is used as the key for determining which queue to add the runnable.

Parameters:

runnable - The element to run when interval expires.

interval - The queue to add the runnable to.

Throws:

RuntimeException - Thrown if an error occurs adding the element to the queue.

schedule

public void schedule(long interval,
            ReadyRunnable runnable)

schedule

This method is used to schedule a ready runnable in the system. The interval is used as the key for determining which queue to add the runnable.

Specified by:

schedule in interface ScheduleTimer

Parameters:

interval - a long.

runnable - a ReadyRunnable object.

unschedule

public void unschedule(ReadyRunnable runnable)

This method is used to unschedule a ready runnable in the system. The runnuble is removed from all queue interval where is found.

Parameters:

runnable - The element to remove from queue intervals.

unschedule

public void unschedule(ReadyRunnable runnable,
              long interval)

This method is used to unschedule a ready runnable in the system. The interval is used as the key for determining which queue to remove the runnable.

Parameters:

interval - The queue to add the runnable to.

runnable - The element to remove.

getReadyRunnable

public ReadyRunnable getReadyRunnable(ReadyRunnable runnable)

This method is used to get a ready runnable in the system.

Parameters:

runnable - The element to get from queues interval.

Returns:

a ReadyRunnable object.

getReadyRunnable

public ReadyRunnable getReadyRunnable(ReadyRunnable runnable,
                             long interval)

getReadyRunnable

Parameters:

runnable - a ReadyRunnable object.

interval - a long.

Returns:

a ReadyRunnable object.

getCurrentTime

public long getCurrentTime()

This returns the current time for the scheduler

Specified by:

getCurrentTime in interface Timer

Returns:

a long.

start

public void start()

Starts the fiber.

Specified by:

start in interface Fiber

Throws:

IllegalStateException - Thrown if the fiber is already running.

stop

public void stop()

Stops the fiber. If the fiber has never been run then an exception is generated.

Specified by:

stop in interface Fiber

Throws:

IllegalStateException - Throws if the fiber has never been started.

pause

public void pause()

Pauses the scheduler if it is current running. If the fiber has not been run or has already stopped then an exception is generated.

Specified by:

pause in interface PausableFiber

Throws:

IllegalStateException - Throws if the operation could not be completed due to the fiber's state.

resume

public void resume()

Resumes the scheduler if it has been paused. If the fiber has not been run or has already stopped then an exception is generated.

Specified by:

resume in interface PausableFiber

Throws:

IllegalStateException - Throws if the operation could not be completed due to the fiber's state.

getStatus

public int getStatus()

Returns the current of this fiber.

Specified by:

getStatus in interface Fiber

Returns:

The current status.

getName

public String getName()

Returns the name of this fiber.

Specified by:

getName in interface Fiber

Returns:

a String object.

run

public void run()

The main method of the scheduler. This method is responsible for checking the runnable queues for ready objects and then enqueuing them into the thread pool for execution.

Specified by:

run in interface Runnable