timersscheduling

Timer scheduling is a technique in computer systems for deferring or repeating the execution of tasks until a specified time or after a given delay. It is implemented through timer facilities provided by operating systems, runtimes, or event-driven frameworks. A timer typically comprises a reference or handle, an expiration time (or deadline), a callback or task to run, and optional repetition parameters. Timers can be one-shot, firing once, or periodic, firing at regular intervals.

Timer management relies on a data structure that stores timers in order of their expiration. Common approaches include a min-heap (priority queue), a timing wheel, or a bucketed queue. The system uses a monotonic clock to avoid errors from wall-clock changes, and upon reaching the next expiration, the corresponding callback is scheduled for execution, either by a thread pool, the event loop, or a dedicated timer thread.

Use cases include delaying work until a future time, implementing timeouts for I/O or network operations, performing periodic maintenance tasks, and implementing retry or backoff strategies. Timers are central to asynchronous programming and real-time systems, but they introduce challenges such as timer granularity, jitter, cancellation race conditions, and resource leaks if not managed carefully.

Examples: In Java, one can use Timer/TimerTask or ScheduledExecutorService; in JavaScript, setTimeout and setInterval; in Python, threading.Timer or asyncio call_later/call_at. See also: event loop, deadline scheduling, and real-time scheduling.