gh-czlonkowski-n8n-skills/skills/n8n-workflow-patterns/scheduled_tasks.md

Scheduled Tasks Pattern

Use Case: Recurring automation workflows that run automatically on a schedule.

---

Pattern Structure

Schedule Trigger → [Fetch Data] → [Process] → [Deliver] → [Log/Notify]

Key Characteristic: Time-based automated execution

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Core Components

1. Schedule Trigger

Purpose: Execute workflow at specified times

Modes:

• Interval - Every X minutes/hours/days
• Cron - Specific times (advanced)
• Days & Hours - Simple recurring schedule

2. Data Source

Common sources:

• HTTP Request (APIs)
• Database queries
• File reads
• Service-specific nodes

3. Processing

Typical operations:

• Filter/transform data
• Aggregate statistics
• Generate reports
• Check conditions

4. Delivery

Output channels:

• Email
• Slack/Discord/Teams
• File storage
• Database writes

5. Logging

Purpose: Track execution history

Methods:

• Database log entries
• File append
• Monitoring service

---

Schedule Configuration

Interval Mode

Best for: Simple recurring tasks

Examples:

// Every 15 minutes
{
  mode: "interval",
  interval: 15,
  unit: "minutes"
}

// Every 2 hours
{
  mode: "interval",
  interval: 2,
  unit: "hours"
}

// Every day at midnight
{
  mode: "interval",
  interval: 1,
  unit: "days"
}

Days & Hours Mode

Best for: Specific days and times

Examples:

// Weekdays at 9 AM
{
  mode: "daysAndHours",
  days: ["monday", "tuesday", "wednesday", "thursday", "friday"],
  hour: 9,
  minute: 0
}

// Every Monday at 6 PM
{
  mode: "daysAndHours",
  days: ["monday"],
  hour: 18,
  minute: 0
}

Cron Mode (Advanced)

Best for: Complex schedules

Examples:

// Every weekday at 9 AM
{
  mode: "cron",
  expression: "0 9 * * 1-5"
}

// First day of every month at midnight
{
  mode: "cron",
  expression: "0 0 1 * *"
}

// Every 15 minutes during business hours (9 AM - 5 PM) on weekdays
{
  mode: "cron",
  expression: "*/15 9-17 * * 1-5"
}

Cron format: minute hour day month weekday

• * = any value
• */15 = every 15 units
• 1-5 = range (Monday-Friday)
• 1,15 = specific values

Cron examples:

0 */6 * * *      Every 6 hours
0 9,17 * * *     At 9 AM and 5 PM daily
0 0 * * 0        Every Sunday at midnight
*/30 * * * *     Every 30 minutes
0 0 1,15 * *     1st and 15th of each month

---

Common Use Cases

1. Daily Reports

Flow: Schedule → Fetch data → Aggregate → Format → Email

Example (Sales report):

1. Schedule (daily at 9 AM)

2. Postgres (query yesterday's sales)
   SELECT date, SUM(amount) as total, COUNT(*) as orders
   FROM orders
   WHERE date = CURRENT_DATE - INTERVAL '1 day'
   GROUP BY date

3. Code (calculate metrics)
   - Total revenue
   - Order count
   - Average order value
   - Comparison to previous day

4. Set (format email body)
   Subject: Daily Sales Report - {{$json.date}}
   Body: Formatted HTML with metrics

5. Email (send to team@company.com)

6. Slack (post summary to #sales)

2. Data Synchronization

Flow: Schedule → Fetch from source → Transform → Write to target

Example (CRM to data warehouse sync):

1. Schedule (every hour)

2. Set (store last sync time)
   SELECT MAX(synced_at) FROM sync_log

3. HTTP Request (fetch new CRM contacts since last sync)
   GET /api/contacts?updated_since={{$json.last_sync}}

4. IF (check if new records exist)

5. Set (transform CRM schema to warehouse schema)

6. Postgres (warehouse - INSERT new contacts)

7. Postgres (UPDATE sync_log SET synced_at = NOW())

8. IF (error occurred)
   └─ Slack (alert #data-team)

3. Monitoring & Health Checks

Flow: Schedule → Check endpoints → Alert if down

Example (Website uptime monitor):

1. Schedule (every 5 minutes)

2. HTTP Request (GET https://example.com/health)
   - timeout: 10 seconds
   - continueOnFail: true

3. IF (status !== 200 OR response_time > 2000ms)

4. Redis (check alert cooldown - don't spam)
   - Key: alert:website_down
   - TTL: 30 minutes

5. IF (no recent alert sent)

6. [Alert Actions]
   ├─ Slack (notify #ops-team)
   ├─ PagerDuty (create incident)
   ├─ Email (alert@company.com)
   └─ Redis (set alert cooldown)

7. Postgres (log uptime check result)

4. Cleanup & Maintenance

Flow: Schedule → Find old data → Archive/Delete → Report

Example (Database cleanup):

1. Schedule (weekly on Sunday at 2 AM)

2. Postgres (find old records)
   SELECT * FROM logs
   WHERE created_at < NOW() - INTERVAL '90 days'
   LIMIT 10000

3. IF (records exist)

4. Code (export to JSON for archive)

5. Google Drive (upload archive file)
   - Filename: logs_archive_{{$now.format('YYYY-MM-DD')}}.json

6. Postgres (DELETE archived records)
   DELETE FROM logs
   WHERE id IN ({{$json.archived_ids}})

7. Slack (report: "Archived X records, deleted Y records")

5. Data Enrichment

Flow: Schedule → Find incomplete records → Enrich → Update

Example (Enrich contacts with company data):

1. Schedule (nightly at 3 AM)

2. Postgres (find contacts without company data)
   SELECT id, email, domain FROM contacts
   WHERE company_name IS NULL
   AND created_at > NOW() - INTERVAL '7 days'
   LIMIT 100

3. Split In Batches (10 contacts per batch)

4. HTTP Request (call Clearbit enrichment API)
   - For each contact domain
   - Rate limit: wait 1 second between batches

5. Set (map API response to database schema)

6. Postgres (UPDATE contacts with company data)

7. Wait (1 second - rate limiting)

8. Loop (back to step 4 until all batches processed)

9. Email (summary: "Enriched X contacts")

6. Backup Automation

Flow: Schedule → Export data → Compress → Store → Verify

Example (Database backup):

1. Schedule (daily at 2 AM)

2. Code (execute pg_dump)
   const { exec } = require('child_process');
   exec('pg_dump -h db.example.com mydb > backup.sql')

3. Code (compress backup)
   const zlib = require('zlib');
   // Compress backup.sql to backup.sql.gz

4. AWS S3 (upload compressed backup)
   - Bucket: backups
   - Key: db/backup-{{$now.format('YYYY-MM-DD')}}.sql.gz

5. AWS S3 (list old backups)
   - Keep last 30 days only

6. AWS S3 (delete old backups)

7. IF (error occurred)
   ├─ PagerDuty (critical alert)
   └─ Email (backup failed!)
   ELSE
   └─ Slack (#devops: "✅ Backup completed")

7. Content Publishing

Flow: Schedule → Fetch content → Format → Publish

Example (Automated social media posts):

1. Schedule (every 3 hours during business hours)
   - Cron: 0 9,12,15,18 * * 1-5

2. Google Sheets (read content queue)
   - Sheet: "Scheduled Posts"
   - Filter: status=pending AND publish_time <= NOW()

3. IF (posts available)

4. HTTP Request (shorten URLs in post)

5. HTTP Request (POST to Twitter API)

6. HTTP Request (POST to LinkedIn API)

7. Google Sheets (update status=published)

8. Slack (notify #marketing: "Posted: {{$json.title}}")

---

Timezone Considerations

Set Workflow Timezone

// In workflow settings
{
  timezone: "America/New_York"  // EST/EDT
}

Common Timezones

America/New_York    - Eastern (US)
America/Chicago     - Central (US)
America/Denver      - Mountain (US)
America/Los_Angeles - Pacific (US)
Europe/London       - GMT/BST
Europe/Paris        - CET/CEST
Asia/Tokyo          - JST
Australia/Sydney    - AEDT
UTC                 - Universal Time

Handle Daylight Saving

Best practice: Use timezone-aware scheduling

// ❌ Bad: UTC schedule for "9 AM local"
// Will be off by 1 hour during DST transitions

// ✅ Good: Set workflow timezone
{
  timezone: "America/New_York",
  schedule: {
    mode: "daysAndHours",
    hour: 9  // Always 9 AM Eastern, regardless of DST
  }
}

---

Error Handling

Pattern 1: Error Trigger Workflow

Main workflow: Normal execution Error workflow: Alerts and recovery

Main:

Schedule → Fetch → Process → Deliver

Error:

Error Trigger (for main workflow)
  → Set (extract error details)
  → Slack (#ops-team: "❌ Scheduled job failed")
  → Email (admin alert)
  → Postgres (log error for analysis)

Pattern 2: Retry with Backoff

Schedule → HTTP Request (continueOnFail: true)
  → IF (error)
    ├─ Wait (5 minutes)
    ├─ HTTP Request (retry 1)
    └─ IF (still error)
      ├─ Wait (15 minutes)
      ├─ HTTP Request (retry 2)
      └─ IF (still error)
        └─ Alert admin

Pattern 3: Partial Failure Handling

Schedule → Split In Batches
  → Process (continueOnFail: true)
  → Code (track successes and failures)
  → Report:
    "✅ Processed: 95/100"
    "❌ Failed: 5/100"

---

Performance Optimization

1. Batch Processing

For large datasets:

Schedule → Query (LIMIT 10000)
  → Split In Batches (100 items)
  → Process batch
  → Loop

2. Parallel Processing

When operations are independent:

Schedule
  ├─ [Branch 1: Update DB]
  ├─ [Branch 2: Send emails]
  └─ [Branch 3: Generate report]
  → Merge (wait for all) → Final notification

3. Skip if Already Running

Prevent overlapping executions:

Schedule → Redis (check lock)
  → IF (lock exists)
    └─ End (skip this execution)
  → ELSE
    ├─ Redis (set lock, TTL 30 min)
    ├─ [Execute workflow]
    └─ Redis (delete lock)

4. Early Exit on No Data

Don't waste time if nothing to process:

Schedule → Query (check if work exists)
  → IF (no results)
    └─ End workflow (exit early)
  → ELSE
    └─ Process data

---

Monitoring & Logging

Pattern 1: Execution Log Table

CREATE TABLE workflow_executions (
  id SERIAL PRIMARY KEY,
  workflow_name VARCHAR(255),
  started_at TIMESTAMP,
  completed_at TIMESTAMP,
  status VARCHAR(50),
  records_processed INT,
  error_message TEXT
);

Log execution:

Schedule
  → Set (record start)
  → [Workflow logic]
  → Postgres (INSERT execution log)

Pattern 2: Metrics Collection

Schedule → [Execute]
  → Code (calculate metrics)
    - Duration
    - Records processed
    - Success rate
  → HTTP Request (send to monitoring system)
    - Datadog, Prometheus, etc.

Pattern 3: Summary Notifications

Daily/weekly execution summaries:

Schedule (daily at 6 PM) → Query execution logs
  → Code (aggregate today's executions)
  → Email (summary report)
    "Today's Workflow Executions:
     - 24/24 successful
     - 0 failures
     - Avg duration: 2.3 min"

---

Testing Scheduled Workflows

1. Use Manual Trigger for Testing

Development pattern:

Manual Trigger (for testing)
  → [Same workflow logic]
  → [Outputs]

// Once tested, replace with Schedule Trigger

2. Test with Different Times

// Code node - simulate different times
const testTime = new Date('2024-01-15T09:00:00Z');
return [{ json: { currentTime: testTime } }];

3. Dry Run Mode

Schedule → Set (dryRun: true)
  → IF (dryRun)
    └─ Log what would happen (don't execute)
  → ELSE
    └─ Execute normally

4. Shorter Interval for Testing

// Testing: every 1 minute
{
  mode: "interval",
  interval: 1,
  unit: "minutes"
}

// Production: every 1 hour
{
  mode: "interval",
  interval: 1,
  unit: "hours"
}

---

Common Gotchas

1. ❌ Wrong: Ignoring timezone

Schedule (9 AM)  // 9 AM in which timezone?

✅ Correct: Set workflow timezone

// Workflow settings
{
  timezone: "America/New_York"
}

2. ❌ Wrong: Overlapping executions

Schedule (every 5 min) → Long-running task (10 min)
// Two executions running simultaneously!

✅ Correct: Add execution lock

Schedule → Redis (check lock)
  → IF (locked) → Skip
  → ELSE → Execute

3. ❌ Wrong: No error handling

Schedule → API call → Process (fails silently)

✅ Correct: Add error workflow

Main: Schedule → Execute
Error: Error Trigger → Alert

4. ❌ Wrong: Processing all data at once

Schedule → SELECT 1000000 records → Process (OOM)

✅ Correct: Batch processing

Schedule → SELECT with pagination → Split In Batches → Process

5. ❌ Wrong: Hardcoded dates

query: "SELECT * FROM orders WHERE date = '2024-01-15'"

✅ Correct: Dynamic dates

query: "SELECT * FROM orders WHERE date = CURRENT_DATE - INTERVAL '1 day'"

---

Real Template Examples

From n8n template library:

Template #2947 (Weather to Slack):

Schedule (daily 8 AM)
  → HTTP Request (weather API)
  → Set (format message)
  → Slack (post to #general)

Daily backup:

Schedule (nightly 2 AM)
  → Postgres (export data)
  → Google Drive (upload)
  → Email (confirmation)

Monitoring:

Schedule (every 5 min)
  → HTTP Request (health check)
  → IF (down) → PagerDuty alert

Use search_templates({query: "schedule"}) to find more!

---

Checklist for Scheduled Workflows

Planning

• Define schedule frequency (interval, cron, days & hours)
• Set workflow timezone
• Estimate execution duration
• Plan for failures and retries
• Consider timezone and DST

Implementation

• Configure Schedule Trigger
• Set workflow timezone in settings
• Add early exit for no-op cases
• Implement batch processing for large data
• Add execution logging

Error Handling

• Create Error Trigger workflow
• Implement retry logic
• Add alert notifications
• Log errors for analysis
• Handle partial failures gracefully

Monitoring

• Log each execution (start, end, status)
• Track metrics (duration, records, success rate)
• Set up daily/weekly summaries
• Alert on consecutive failures
• Monitor resource usage

Testing

• Test with Manual Trigger first
• Verify timezone behavior
• Test error scenarios
• Check for overlapping executions
• Validate output quality

Deployment

• Document workflow purpose
• Set up monitoring
• Configure alerts
• Activate workflow in n8n UI ⚠️ Manual activation required (API/MCP cannot activate)
• Test in production (short interval first)
• Monitor first few executions

---

Advanced Patterns

Dynamic Scheduling

Change schedule based on conditions:

Schedule (check every hour) → Code (check if it's time to run)
  → IF (business hours AND weekday)
    └─ Execute workflow
  → ELSE
    └─ Skip

Dependent Schedules

Chain workflows:

Workflow A (daily 2 AM): Data sync
  → On completion → Trigger Workflow B

Workflow B: Generate report (depends on fresh data)

Conditional Execution

Skip based on external factors:

Schedule → HTTP Request (check feature flag)
  → IF (feature enabled)
    └─ Execute
  → ELSE
    └─ Skip

---

Summary

Key Points:

1. Set workflow timezone explicitly
2. Batch processing for large datasets
3. Error handling is critical (Error Trigger + retries)
4. Prevent overlaps with execution locks
5. Monitor and log all executions

Pattern: Schedule → Fetch → Process → Deliver → Log

Schedule Modes:

• Interval: Simple recurring (every X minutes/hours)
• Days & Hours: Specific days and times
• Cron: Advanced complex schedules

Related:

• http_api_integration.md - Fetching data on schedule
• database_operations.md - Scheduled database tasks
• webhook_processing.md - Alternative to scheduling