Scheduled-task pattern: Difference between revisions

Revision as of 07:10, 9 November 2008

Revision as of 00:09, 2 August 2009

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'''Intent:''' Ensure that desired operations are performed at specific points in the future.

{{Unreferenced|date=November 2008}}

In RealTime systems, it is often necessary to ensure that something is done at a specific time. A scheduler object (note: not quite the same as SchedulerPattern) keeps track of these actions, and invokes them at the appropriate times.

A '''scheduled-task pattern''' is a type of [[design pattern (computer science)|software design pattern]] used with real-time systems. It is not to be confused with the "[[scheduler pattern]]".

Times may be expressed as "wall time" or as some sort of internal time ("ticks", milliseconds-since-startup, etc.).

While the [[scheduler pattern]] delays access to a resource (be it a function, variable, or otherwise) only as long as absolutely needed, the scheduled-task pattern delays execution until a determined time. This is important in real-time systems for a variety of reasons.

If highly accurate scheduling of tasks is needed (to milliseconds or less), the scheduler task needs to run at a very high priority, or be hooked into a high-frequency interrupt routine.

==See also==

*[[Command pattern]]

*[[Memento pattern]]

''Is there another, more common name for this pattern?''

[[Category:Software design patterns]]

'''See also:''' CommandPattern, MementoPattern

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The PPR has MartinFowler's "Recurring Events" document at http://c2.com/ppr/schedule.pdf

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CategoryPattern | CategoryBehavioralPatterns | CategoryRealTimePatterns

*[[CommandScheduled-task pattern]]