Creating a basic DAG file in Apache Airflow - Practice Exercises

Challenge - 5 Problems

💻 Command Output

intermediate

Output of a simple Airflow DAG run

Given this Airflow DAG code, what will be the output when the task runs successfully?

Apache Airflow

from airflow import DAG
from airflow.operators.python import PythonOperator
from datetime import datetime

def greet():
    print('Hello from Airflow!')

default_args = {
    'start_date': datetime(2024, 1, 1)
}

dag = DAG('greet_dag', default_args=default_args, schedule_interval='@daily')

task = PythonOperator(
    task_id='greet_task',
    python_callable=greet,
    dag=dag
)

A Hello from Airflow!

B Task greet_task failed

C SyntaxError: invalid syntax

D No output because DAG is paused

💡 Hint

The PythonOperator runs the greet function which prints a message.

The greet function prints 'Hello from Airflow!' when the task runs successfully.

🧠 Conceptual

intermediate

Understanding DAG schedule_interval

What does the schedule_interval='@hourly' mean in an Airflow DAG?

A The DAG runs once every minute

B The DAG runs once every day

C The DAG runs once every hour

D The DAG runs only once at start_date

💡 Hint

Think about how often '@hourly' triggers the DAG.

'@hourly' is a preset that schedules the DAG to run once every hour.

❓ Configuration

advanced

Correct DAG default_args configuration

Which option correctly sets the default_args for an Airflow DAG with a start date of January 1, 2024, and retries set to 3?

A {'start_date': datetime(2024, 1, 1), 'retries': 3}

B {'start_date': '2024-01-01', 'retries': '3'}

C {start_date: datetime(2024, 1, 1), retries: 3}

D {'start_date': datetime(2024, 1, 1), retries: 'three'}

💡 Hint

Check the types of values and syntax for dictionary keys and values.

Option A uses correct Python dictionary syntax with proper types for start_date and retries.

❓ Troubleshoot

advanced

Identifying error in DAG task definition

What error will occur with this task definition in an Airflow DAG? from airflow.operators.python import PythonOperator task = PythonOperator( task_id='task1' python_callable=lambda: print('Hi') dag=dag )

A NameError: name 'dag' is not defined

B SyntaxError: missing comma between arguments

C TypeError: python_callable must be a function

D No error, task will run successfully

💡 Hint

Look carefully at the commas separating arguments in the function call.

The task definition is missing commas between arguments, causing a SyntaxError.

🔀 Workflow

expert

Order of steps to create and run a basic Airflow DAG

What is the correct order of steps to create and run a basic Airflow DAG?

A 1,3,2,4

B 3,2,1,4

C 2,1,3,4

D 1,2,3,4

💡 Hint

Think about writing code first, then placing it, then starting services, then running.

You first write the DAG file, then place it in the DAGs folder, start Airflow services, then trigger the DAG.