⏰ Scheduler (daemon)

📌 Description

The task scheduler inside the daemon: running operations on a schedule (cron syntax) and managing the node's background task queue. Used by backups, certificate renewal, auto-updates and user-defined tasks.

🎯 Scenarios

• ⏰ A daily backup at 03:00 (a policy from the platform).
• 🔁 A daily check of Let's Encrypt certificate expiry.
• 🔄 A daemon auto-update — postponed while there are active tasks; --force to run anyway.
• 🧩 A user cron task: asc task add "0 5 * * *" -- ./cleanup.sh.

🏗️ Technical design

✅ First increment (shipped): schedule evaluator + backups

Implemented in src/daemon/scheduler/ and started from the daemon's main loop:

• Evaluator: wakes up at the start of every minute and runs whatever is due; a pass runs on the blocking pool and failures are logged per app — one broken app never stops the rest. Duplicate runs within one minute (fast loop, clock step) are deduplicated by wall-clock minute.
• Schedule syntax (Schedule::parse): daily@HH:MM, bare HH:MM (same as daily) or a five-field cron expression minute hour day-of-month month day-of-week with *, values, a-b ranges, a,b,c lists and /n steps; day-of-week 0–7 (0 and 7 are Sunday). Both date fields restricted follows the vixie-cron rule: either may match. Times are the node's local time.
• Consumer — scheduled backups (DMN-009): every app whose backup policy (asc app settings, category backups) has a schedule gets backups created to the policy's storages with its keep rotation. The settings editor validates the schedule syntax on input.

📝 Next increments (planned)

• Task types: Install, Update, Uninstall, Backup, Restore, CertRenew, Custom.
• States: Pending → Running → Completed | Failed | Cancelled; priorities Low/Normal/High/Critical.
• Queue: prioritized, persistent (SQLite) — survives a daemon restart; unfinished tasks are correctly resumed or marked Failed.
• Schedules: one-off delayed tasks in addition to cron.
• Concurrency: mutually exclusive tasks (two operations on one application) are serialized; auto-update waits for an empty queue.
• CLI: asc task list|add|cancel|info; the API — for the platform's taskmanager (task statuses are streamed upward).

🔗 Related tasks

DMN-012, TASK-001, BE-005, BE-006 in ROADMAP.md.