ReadMeABook/documentation/backend/services/scheduler.md

Recurring Jobs Scheduler

Status: ✅ Implemented

Manages recurring/scheduled jobs providing automated tasks (Plex scans, Audible refresh) with scheduled (cron) execution and manual triggering.

Recent Updates

• Config validation before job execution
• Audible refresh persists to database
• Enhanced error handling with clear messages
• Schedule editing UI with toast notifications
• Human-friendly schedule descriptions and editor (preset/custom/advanced modes)
• Real-time cron expression preview

Scheduled Jobs

1. plex_library_scan - Default: every 6 hours, full library scan, disabled by default (enable after setup)
2. plex_recently_added_check - Default: every 5 minutes, lightweight polling of top 10 recently added items, enabled by default
3. audible_refresh - Default: daily midnight, fetches 200 popular + 200 new releases, stores with rankings, disabled by default
4. retry_missing_torrents - Default: daily midnight, re-searches 'awaiting_search' status (limit 50), handles both audiobook and ebook requests, enabled by default
5. retry_failed_imports - Default: every 6 hours, re-attempts 'awaiting_import' status (limit 50), enabled by default
6. cleanup_seeded_torrents - Default: every 30 mins, deletes torrents after seeding requirements met, respects seeding_time_minutes config (0 = never), enabled by default
7. monitor_rss_feeds - Default: every 15 mins, checks RSS feeds from enabled indexers, matches against 'awaiting_search' requests (audiobook and ebook, limit 100), triggers appropriate search jobs for matches, enabled by default

Architecture: Bull + Cron

• Repeatable jobs with cron expressions (Bull's built-in scheduler)
• Manual trigger capability
• Job persistence and retry logic
• Admin UI management
• Automatic scheduling/unscheduling when jobs enabled/disabled
• Schedule updates handled by unscheduling old job and scheduling new one

Human-Friendly Scheduling UI

Three Modes:

1. Common Schedules - Preset options (every 15min, hourly, daily, weekly, monthly)
2. Custom Schedule - Visual builder with dropdowns for minutes/hours/daily/weekly/monthly
3. Advanced (Cron) - Raw cron expression for power users

Features:

• Human-readable display: "Every 6 hours" instead of "0 */6 * * *"
• Real-time preview of cron expressions
• Visual schedule builder (no cron knowledge required)
• Cron validation before saving
• Shows both human text and cron expression in job list

Utility Functions (src/lib/utils/cron.ts):

• cronToHuman(cron) - Converts cron to readable text
• customScheduleToCron(schedule) - Builds cron from visual inputs (auto-converts 24+ hour intervals to daily)
• cronToCustomSchedule(cron) - Parses cron to visual inputs
• isValidCron(cron) - Validates cron expression

Cron Expressions

* * * * *
│ │ │ │ └─ day of week (0-7)
│ │ │ └─── month (1-12)
│ │ └───── day of month (1-31)
│ └─────── hour (0-23)
└───────── minute (0-59)

Examples:

• 0 */6 * * * - Every 6 hours
• 0 0 * * * - Daily midnight
• */30 * * * * - Every 30 mins

API Endpoints

GET /api/admin/jobs - Get all scheduled jobs (admin auth)

POST /api/admin/jobs - Create job (admin auth)

{
  "name": "Daily Audible Refresh",
  "type": "audible_refresh",
  "schedule": "0 0 * * *",
  "enabled": true
}

PUT /api/admin/jobs/:id - Update job (admin auth)

DELETE /api/admin/jobs/:id - Delete job (admin auth)

POST /api/admin/jobs/:id/trigger - Manually trigger job (admin auth)

GET /api/admin/jobs/:id/history?limit=50 - Job execution history (admin auth)

Data Model

interface ScheduledJob {
  id: string;
  name: string;
  type: JobType;
  schedule: string; // cron
  enabled: boolean;
  lastRun: Date | null;
  nextRun: Date | null;
  payload: any;
}

Implementation Details

Scheduler Service (scheduler.service.ts):

• start(): Initializes scheduler, creates default jobs, schedules all enabled jobs
• scheduleJob(): Adds job to Bull as repeatable job with cron expression
• unscheduleJob(): Removes repeatable job from Bull
• updateScheduledJob(): Unschedules old job, updates DB, schedules new job if enabled
• deleteScheduledJob(): Unschedules job before deleting from DB

Job Queue Service (job-queue.service.ts):

• addRepeatableJob(): Registers job type with Bull's repeat scheduler
• removeRepeatableJob(): Removes job from Bull's repeat scheduler
• Processors for each scheduled job type call scheduler.triggerJobNow()
• setMaxListeners(20): Set on both Redis client and Bull queue to accommodate 12 job processors (6 regular + 6 scheduled)

Flow:

1. App starts → scheduler.start() → schedules all enabled jobs
2. Bull triggers job at cron time → processor calls triggerJobNow()
3. triggerJobNow() executes job-specific logic (Plex scan, Audible refresh, etc.)
4. Updates lastRun timestamp in database

Audible Refresh Processor

Implementation:

1. Fetch 200 popular + 200 new releases (multi-page scraping)
2. Download and cache cover thumbnails locally (stored in /app/cache/thumbnails)
3. Wipe and re-populate AudibleCacheCategory entries with reserved IDs (__popular__, __new_releases__) and user-configured category IDs
4. Upsert book metadata in AudibleCache, ranked entries in AudibleCacheCategory
5. Record sync timestamp (lastAudibleSync)
6. Clean up unused thumbnails (removes covers for audiobooks no longer in cache)
7. Perform fuzzy matching (70% threshold) against Plex library
8. Set plexGuid when match found (with duplicate protection)
9. Update availabilityStatus to 'available' or 'unknown'

Duplicate PlexGuid Handling: Since plexGuid has UNIQUE constraint, only first match gets assigned to prevent violations.

Thumbnail Caching: Downloads cover images from Audible and stores them locally to reduce external requests. Cached thumbnails are served via /api/cache/thumbnails/[filename] endpoint. Unused thumbnails are automatically cleaned up after each sync.

Fixed Issues ✅

• ✅ Jobs running without config validation
• ✅ Default alert() popups → toast notifications
• ✅ No UI for editing schedules → added edit modal
• ✅ Audible data not persisting → saves to database
• ✅ Download progress logging ~500x/s → 10s delay
• ✅ Requests failing permanently (no torrents) → retry system with 'awaiting_search'
• ✅ Requests failing permanently (no files) → retry system with max 5 retries + 'warn' status
• ✅ Failed requests blocking re-requests → allow re-requesting failed/warn/cancelled
• ✅ Files deleted immediately → kept until seeding requirements met
• ✅ No seeding time config → added seeding_time_minutes
• ✅ Scheduled jobs not running on schedule → implemented Bull repeatable jobs with cron scheduling
• ✅ MaxListenersExceededWarning → increased maxListeners to 20 on both Redis client and Bull queue
• ✅ Cron expressions not user-friendly → added human-readable descriptions and visual schedule builder
• ✅ Scheduled jobs triggered by timer not appearing in system logs → Job records now created automatically for timer-triggered jobs
• ✅ Scheduled jobs triggered by timer not updating lastRun timestamp → Job queue now updates lastRun when processing timer-triggered jobs
• ✅ Daily cron patterns at non-midnight hours not recognized → Fixed getIntervalFromCron to parse any daily time (e.g., "0 4 * * *")
• ✅ "Every 24 hours" interval validation error → Auto-converts 24+ hour intervals to daily schedule (0 0 * * *)

Tech Stack

• Bull repeatable jobs
• PostgreSQL (scheduled_jobs table)
• Bull/Redis infrastructure