Timetables for complex schedules in Apache Airflow - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a Timetable in Apache Airflow?

A Timetable in Airflow defines when and how often a workflow (DAG) should run. It controls the schedule beyond simple cron expressions, allowing complex timing rules.

intermediate

How does a Timetable differ from a cron schedule in Airflow?

A cron schedule is a simple string defining fixed times, while a Timetable is a Python class that can generate complex schedules dynamically, like irregular intervals or event-based triggers.

intermediate

Which method must be implemented in a custom Airflow Timetable class?

The method 'next_dagrun_info' must be implemented. It returns the next scheduled run time and optional metadata for the DAG run.

advanced

What is the role of 'logical_date' in Airflow Timetables?

The 'logical_date' represents the scheduled time for a DAG run, not the actual execution time. Timetables use it to calculate the next run time accurately.

advanced

Give an example use case for a custom Timetable in Airflow.

When you need to run a DAG on complex patterns like 'every first Monday of the month' or 'only on business days excluding holidays', a custom Timetable can handle these rules.

What does an Airflow Timetable primarily control?

A The resources used by a DAG

B The order of tasks inside a DAG

C When and how often a DAG runs

D The logs generated by a DAG

A Timetable defines the schedule for DAG runs, controlling when and how often they execute.

Which method must a custom Timetable class implement?

A start_dag

B execute_task

C get_logs

D next_dagrun_info

The 'next_dagrun_info' method returns the next scheduled run time for the DAG.

What is the 'logical_date' in Airflow scheduling?

A The scheduled time for a DAG run

B The actual time a task starts

C The time a DAG finishes

D The current system time

Logical date is the scheduled time Airflow uses to identify DAG runs, not the real execution time.

Why use a custom Timetable instead of cron?

A To handle complex or irregular schedules

B To speed up task execution

C To reduce memory usage

D To change task dependencies

Custom Timetables allow defining schedules that cron cannot express, like skipping holidays or irregular intervals.

Which of these is NOT a feature of Airflow Timetables?

A Dynamic schedule generation

B Task retry management

C Support for complex calendar rules

D Custom logic for run times

Task retry management is handled by task settings, not by Timetables.

Explain what an Airflow Timetable is and why you might create a custom one.

Think about when simple cron is not enough.

Describe the role of the 'next_dagrun_info' method in a custom Timetable.

This method is key to scheduling logic.