DAG concept (Directed Acyclic Graph) in Apache Airflow - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does DAG stand for in Airflow?

DAG stands for Directed Acyclic Graph. It is a collection of tasks with a defined order and no cycles.

beginner

Why must a DAG be acyclic?

A DAG must be acyclic to avoid infinite loops in task execution. This ensures tasks run in a clear, one-way order.

beginner

In Airflow, what does the direction in a DAG represent?

The direction shows the order tasks should run. An arrow from Task A to Task B means Task A runs before Task B.

intermediate

How does Airflow use DAGs to manage workflows?

Airflow uses DAGs to define workflows as tasks connected by dependencies. It schedules and runs tasks following the DAG order.

intermediate

What happens if a cycle is introduced in an Airflow DAG?

Airflow will raise an error because cycles cause tasks to depend on themselves, making execution impossible.

What is a key property of a DAG in Airflow?

A It has only one task

B It allows tasks to run in any order

C It repeats tasks infinitely

D It has no cycles

A DAG must have no cycles to ensure tasks run in a clear, one-way order.

In a DAG, what does an arrow from Task A to Task B mean?

A Task A runs before Task B

B Tasks run at the same time

C Task B runs before Task A

D Tasks are unrelated

The arrow shows Task A must finish before Task B starts.

Why does Airflow reject DAGs with cycles?

A Cycles speed up execution

B Cycles reduce task dependencies

C Cycles cause infinite loops

D Cycles are allowed in Airflow

Cycles cause infinite loops, making task execution impossible.

What does Airflow use DAGs for?

A To define and schedule workflows

B To store data

C To create user interfaces

D To monitor servers

Airflow uses DAGs to define workflows and schedule tasks in order.

Which of these is NOT true about DAGs?

A They have directed edges

B They can have cycles

C They define task order

D They are used in Airflow

DAGs cannot have cycles; that is what 'acyclic' means.

Explain what a Directed Acyclic Graph (DAG) is and why it is important in Airflow.

Think about how tasks depend on each other and why loops would cause problems.

Describe what happens if you try to create a cycle in an Airflow DAG and why Airflow prevents it.

Consider what would happen if tasks kept waiting for each other forever.