Core Concepts

Core Concepts

Schedulers

The Scheduler is the main entry point. It manages a pool of worker threads and orchestrates task execution.

• Thread Pool: Configurable size via SchedulerSpec.threadCount().
• Time Source: Uses monotonic time (System.nanoTime()) for duration calculations to be immune to system clock shifts.
• Lifecycle: Must be closed via close() to terminate worker threads.

Triggers

Triggers determine when a task runs.

1. OnceTrigger: Fires a single time after a delay.
2. FixedRateTrigger: Fires at regular intervals (e.g., every 5 minutes). If a task takes too long, subsequent executions may bunch up or be skipped depending on policy.
3. FixedDelayTrigger: Fires after a fixed delay after the previous execution completes. Useful for preventing overlap.
4. CronTrigger: Fires based on a calendar schedule (e.g., "Mondays at 9 AM").

Tasks

A task is simply a Runnable. Chronos wraps your runnable to provide:

• History: Tracks run counts, success rates, and last execution times.
• Safety: Catches exceptions to prevent thread death (configurable via ExecutionPolicy).
• Resilience: Can automatically retry upon failure.
• State: Tracks lifecycle states (SCHEDULED, RUNNING, COMPLETED, FAILED, CANCELLED).