The Full Cron Daemon: End-to-End

You've built every piece. The final assembly is a long-running process that:

1. Loads jobs from a config file or database on startup
2. Computes initial next_run for each (with catchup if last_run shows missed instances)
3. Pushes everything onto the min-heap
4. Runs the execution loop:
   • peek at heap head
   • sleep until next firing or 60s, whichever sooner
   • run all jobs whose next_run has passed (respecting overlap policy)
   • push each back with new next_run
5. Handles signals:
   • SIGHUP -> reload config
   • SIGTERM -> drain (wait for running jobs) and exit
6. Persists state every minute so a restart resumes near the right point

Production extras:

• Logging: stdout/stderr of each run captured
• Alerts: notify on N consecutive failures
• Webhooks: call out on success/failure
• HTTP API: query schedule, trigger now, pause/resume

You now understand the moving parts behind cron, kubernetes CronJob, GitHub Actions schedules, AWS EventBridge, and every other "do this thing on a schedule" system.