ExternalTaskSensor for cross-DAG dependencies in Apache Airflow - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import the ExternalTaskSensor from Airflow sensors.

Apache Airflow

from airflow.sensors.external_task import [1]

Drag options to blanks, or click blank then click option'

AExternalTaskSensor

BExternalSensorTask

CTaskSensorExternal

DExternalTask

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong class names like ExternalSensorTask or ExternalTask.

The correct import is ExternalTaskSensor from airflow.sensors.external_task.

2fill in blank

medium

Complete the ExternalTaskSensor to wait for a task named 'task_b' in DAG 'dag_b'.

Apache Airflow

wait_for_task = ExternalTaskSensor(
    task_id='wait_for_task_b',
    external_dag_id='[1]',
    external_task_id='task_b',
    mode='reschedule'
)

Drag options to blanks, or click blank then click option'

Atask_a

Bdag_a

Cdag_b

Dtask_b

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing external_dag_id with external_task_id.

The external_dag_id should be the DAG where the task to wait for lives, which is 'dag_b'.

3fill in blank

hard

Fix the error in the ExternalTaskSensor mode parameter to avoid blocking the worker.

Apache Airflow

wait_for_task = ExternalTaskSensor(
    task_id='wait_for_task_c',
    external_dag_id='dag_c',
    external_task_id='task_c',
    mode='[1]'
)

Drag options to blanks, or click blank then click option'

Apoke

Breschedule

Cblock

Dwait

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'poke' mode which blocks the worker.

Using mode='reschedule' allows the sensor to free the worker slot while waiting, preventing blocking.

4fill in blank

hard

Fill both blanks to create an ExternalTaskSensor that waits for 'task_x' in 'dag_x' with a 600 seconds timeout.

Apache Airflow

wait_task = ExternalTaskSensor(
    task_id='wait_task_x',
    external_dag_id='[1]',
    external_task_id='[2]',
    timeout=600
)

Drag options to blanks, or click blank then click option'

Adag_x

Btask_x

Cdag_y

Dtask_y

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping DAG and task names.

The sensor waits for task_x in dag_x, so those values fill the blanks.

5fill in blank

hard

Fill all three blanks to create a dictionary comprehension that maps task ids to their ExternalTaskSensor instances for tasks 'task1' and 'task2' in 'dag_main'.

Apache Airflow

sensors = {
    '[1]': ExternalTaskSensor(
        task_id='wait_[1]',
        external_dag_id='[2]',
        external_task_id='[1]'
    )
    for [3] in ['task1', 'task2']
}

Drag options to blanks, or click blank then click option'

Atask

Bdag_main

Ctask_id

Attempts:

3 left

💡 Hint

Common Mistakes

Using different variable names inconsistently.

The variable name for iteration is 'task' (option D), the DAG id is 'dag_main' (option B), and the dictionary keys and sensor task ids use the iteration variable 'task'.