Package org.eclipse.jetty.io

Class CyclicTimeout

java.lang.Object
org.eclipse.jetty.io.CyclicTimeout
All Implemented Interfaces:
Destroyable
Direct Known Subclasses:
TimeoutCompleteListener
public abstract class CyclicTimeout extends Object implements Destroyable

An abstract implementation of a timeout.

Subclasses should implement onTimeoutExpired().

This implementation is optimised assuming that the timeout will mostly be cancelled and then reused with a similar value.

The typical scenario to use this class is when you have events that postpone (by re-scheduling), or cancel then re-schedule, a timeout for a single entity. For example: connection idleness, where for each connection there is a CyclicTimeout and a read/write postpones the timeout; when the timeout expires, the implementation checks against a timestamp if the connection is really idle. Another example: HTTP session expiration, where for each HTTP session there is a CyclicTimeout and at the beginning of the request processing the timeout is canceled (via cancel()), but at the end of the request processing the timeout is re-scheduled.

This implementation has a CyclicTimeout.Timeout holding the time at which the scheduled task should fire, and a linked list of CyclicTimeout.Wakeup, each holding the actual scheduled task.

Calling schedule(long, TimeUnit) the first time will create a Timeout with an associated Wakeup and submit a task to the scheduler. Calling schedule(long, TimeUnit) again with the same or a larger delay will cancel the previous Timeout, but keep the previous Wakeup without submitting a new task to the scheduler, therefore reducing the pressure on the scheduler and avoid it becomes a bottleneck. When the Wakeup task fires, it will see that the Timeout is now in the future and will attach a new Wakeup with the future time to the Timeout, and submit a scheduler task for the new Wakeup.

See Also:

  • Constructor Details

    • CyclicTimeout

      public CyclicTimeout(Scheduler scheduler)
      Parameters:
      scheduler - A scheduler used to schedule wakeups

  • Method Details

    • getScheduler

      public Scheduler getScheduler()

    • schedule

      public boolean schedule(long delay, TimeUnit units)

      Schedules a timeout, even if already set, cancelled or expired.

      If a timeout is already set, it will be cancelled and replaced by the new one.

      Parameters:
      delay - The period of time before the timeout expires.
      units - The unit of time of the period.
      Returns:
      true if the timeout was already set.

    • cancel

      public boolean cancel()

      Cancels this CyclicTimeout so that it won't expire.

      After being cancelled, this CyclicTimeout can be scheduled again.

      Returns:
      true if this CyclicTimeout was scheduled to expire
      See Also:

    • onTimeoutExpired

      public abstract void onTimeoutExpired()

      Invoked when the timeout expires.

    • destroy

      public void destroy()

      Destroys this CyclicTimeout.

      After being destroyed, this CyclicTimeout is not used anymore.

      Specified by:
      destroy in interface Destroyable