schedule_interval in Airflow DAGs

In Apache Airflow, the schedule_interval parameter defines how frequently a DAG should run. Here are the main options and formats you can use:

1. Preset Schedule Intervals (String aliases)

• "@once": Run the DAG only once, regardless of start_date.
• "@hourly": Run the DAG every hour.
• "@daily": Run the DAG once a day at midnight (00:00 UTC).
• "@weekly": Run the DAG once a week at midnight on Sunday (00:00 UTC).
• "@monthly": Run the DAG once a month at midnight on the first day of the month.
• "@quarterly": Run the DAG at midnight on the first day of each quarter (January, April, July, October).
• "@yearly" or "@annually": Run the DAG once a year at midnight on January 1.

2. Cron Expressions (String format)

• You can use cron syntax to define custom schedules. Format: minute hour day month day_of_week.
  • Examples:
    • "0 9 * * *": Run daily at 9:00 AM UTC.
    • "15 14 * * 1": Run every Monday at 14:15 UTC.
    • "0 0 1 * *": Run at midnight on the first day of each month.

3. TimeDelta (Using datetime.timedelta)

• Use timedelta for intervals in hours, minutes, days, etc., instead of a specific time of day.
• Example:

  python
  from datetime import timedelta
  schedule_interval=timedelta(hours=6)  # Runs every 6 hours
  

4. None

• Setting schedule_interval=None means the DAG will only run if manually triggered.

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