Cron Sink

The Cron sink allows you to trigger workflow executions on a schedule using standard cron expressions.

How It Works

Local Mode

When running the desktop app, Flow-Like uses a local scheduler to trigger executions:

┌──────────────┐
│   Flow-Like  │
│   Desktop    │
│  ┌────────┐  │
│  │ Cron   │──┼──► Trigger Execution
│  │ Sched. │  │
│  └────────┘  │
└──────────────┘

Advantages:

• Works offline
• No server required
• Uses local system time

Limitations:

• Computer must be running
• Missed executions when computer is off

Remote Mode

When deployed to a server, the scheduler runs continuously:

┌──────────────┐
│   Flow-Like  │
│    Server    │
│  ┌────────┐  │
│  │ Cron   │──┼──► Trigger Execution
│  │ Sched. │  │
│  └────────┘  │
└──────────────┘

Advantages:

• Runs 24/7
• Reliable execution
• No missed schedules

Configuration Options

| Field | Type | Description | Required | |-------|------|-------------|----------| | expression | string | Cron expression | Yes | | timezone | string | Timezone (e.g., America/New_York) | No | | enabled | boolean | Whether the schedule is active | No |

Cron Expression Format

Standard 5-field cron format:

┌───────────── minute (0 - 59)
│ ┌───────────── hour (0 - 23)
│ │ ┌───────────── day of month (1 - 31)
│ │ │ ┌───────────── month (1 - 12)
│ │ │ │ ┌───────────── day of week (0 - 6) (Sunday = 0)
│ │ │ │ │
│ │ │ │ │
* * * * *

Special Characters

| Character | Description | Example | |-----------|-------------|---------| | * | Any value | * * * * * (every minute) | | , | List | 1,15,30 * * * * (at 1, 15, 30 min) | | - | Range | 1-5 * * * * (minutes 1-5) | | / | Step | */15 * * * * (every 15 minutes) |

Examples

| Expression | Description | |------------|-------------| | 0 * * * * | Every hour at minute 0 | | 0 9 * * * | Every day at 9:00 AM | | 0 9 * * 1-5 | Weekdays at 9:00 AM | | */15 * * * * | Every 15 minutes | | 0 0 1 * * | First day of month at midnight | | 0 12 * * 0 | Sundays at noon | | 30 4 1,15 * * | 1st and 15th at 4:30 AM |

Timezones

By default, cron expressions use the system timezone (local mode) or server timezone (remote mode). You can override this:

{
  "expression": "0 9 * * *",
  "timezone": "America/New_York"
}

Common Timezones

• UTC - Coordinated Universal Time
• America/New_York - Eastern Time
• America/Los_Angeles - Pacific Time
• Europe/London - British Time
• Europe/Berlin - Central European Time
• Asia/Tokyo - Japan Standard Time

Payload

Cron triggers receive a payload with execution context:

{
  "trigger": "cron",
  "scheduled_time": "2024-01-15T09:00:00Z",
  "actual_time": "2024-01-15T09:00:01Z",
  "expression": "0 9 * * *",
  "timezone": "UTC"
}

Missed Executions

Local Mode Behavior

If the computer was off during a scheduled time:

• Default: The execution is skipped
• Execution resumes at the next scheduled time

Remote Mode Behavior

With proper server infrastructure, missed executions shouldn't occur. However, if the server was down:

• The execution is skipped
• Consider using persistent job queues for critical schedules

Use Cases

Daily Report

Generate and send a daily report every morning:

{
  "expression": "0 8 * * *",
  "timezone": "America/New_York"
}

Hourly Data Sync

Sync data every hour:

{
  "expression": "0 * * * *"
}

Weekly Backup

Run backup every Sunday at 2 AM:

{
  "expression": "0 2 * * 0"
}

End of Month Processing

Process on the last day of each month:

{
  "expression": "0 23 28-31 * *"
}

Note

For true "last day of month" scheduling, you may need workflow logic to check if it's actually the last day.

Monitoring

Checking Schedule Status

The sink status indicates:

• Whether the schedule is active
• Next scheduled execution time
• Last execution time and result

Execution History

All cron executions are logged with:

• Scheduled vs actual execution time
• Run ID for tracking
• Execution result

Best Practices

1. Use specific times when possible - avoid * * * * * unless truly needed
2. Consider timezones - be explicit to avoid confusion
3. Avoid overlapping - ensure previous run completes before next starts
4. Add buffer time - schedule a few minutes after the hour to avoid clock drift issues
5. Monitor execution - check that scheduled jobs are running
6. Test expressions - verify your cron expression does what you expect

Cron Expression Validators

Test your cron expressions:

• crontab.guru - Simple expression explainer
• cronhub.io/cron-expression-generator - Visual builder

Limitations

• Minimum interval: 1 minute
• Maximum schedules per event: Depends on hub configuration
• Execution timeout: Follows standard workflow timeout settings