Trigger rules (all_success, one_success, none_failed) in Apache Airflow - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to set the trigger rule so the task runs only if all upstream tasks succeed.

Apache Airflow

task = PythonOperator(task_id='task1', python_callable=my_func, trigger_rule='[1]')

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

Anone_failed

Ball_done

Cone_success

Dall_success

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'all_done' which runs regardless of success or failure.

Using 'one_success' which runs if any upstream task succeeds.

The all_success trigger rule makes the task run only if all upstream tasks succeed.

2fill in blank

medium

Complete the code to set the trigger rule so the task runs if at least one upstream task succeeds.

Apache Airflow

task = PythonOperator(task_id='task2', python_callable=my_func, trigger_rule='[1]')

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

Anone_failed

Ball_success

Cone_success

Dall_done

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing 'all_success' which requires all upstream tasks to succeed.

Choosing 'none_failed' which requires no failures but all must be done.

The one_success trigger rule runs the task if any one upstream task succeeds.

3fill in blank

hard

Fix the error in the code to make the task run only if no upstream tasks have failed.

Apache Airflow

task = PythonOperator(task_id='task3', python_callable=my_func, trigger_rule='[1]')

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

Anone_failed

Bone_success

Call_success

Dall_done

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'all_success' which requires all upstream tasks to succeed.

Using 'all_done' which runs regardless of failure.

The none_failed trigger rule runs the task if no upstream tasks have failed, even if some are skipped.

4fill in blank

hard

Fill both blanks to create a PythonOperator that runs if all upstream tasks succeed and has a task_id of 'final_task'.

Apache Airflow

task = PythonOperator(task_id='[1]', python_callable=my_func, trigger_rule='[2]')

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

Afinal_task

Ball_done

Call_success

Done_success

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'all_done' as trigger_rule which runs regardless of success.

Using wrong task_id names.

Setting task_id to 'final_task' names the task, and trigger_rule='all_success' ensures it runs only if all upstream tasks succeed.

5fill in blank

hard

Fill all three blanks to create a PythonOperator with task_id 'check_task', that runs if no upstream tasks failed, and uses a callable named 'check_status'.

Apache Airflow

task = PythonOperator(task_id='[1]', python_callable=[2], trigger_rule='[3]')

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

Acheck_task

Bcheck_status

Cnone_failed

Dall_success

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up trigger rules like using 'all_success' instead of 'none_failed'.

Using incorrect callable names.

The task is named 'check_task', uses the function 'check_status', and runs only if no upstream tasks failed using the 'none_failed' trigger rule.

Practice

1. In Airflow, which trigger rule ensures a task runs only if all upstream tasks have succeeded?

easy

A. all_success

B. one_success

C. none_failed

D. all_failed

Solution

1. Step 1: Understand the meaning of all_success

   This trigger rule requires every upstream task to complete successfully before the downstream task runs.

2. Step 2: Compare with other trigger rules

   one_success runs if any upstream succeeds, none_failed runs if no upstream failed (some may be skipped), and all_failed runs only if all upstream failed.

3. Final Answer:

   all_success -> Option A

4. Quick Check:

   All upstream success = all_success [OK]

Hint: All upstream must succeed means all_success [OK]

Common Mistakes:

• Confusing one_success with all_success
• Thinking none_failed means all succeeded
• Assuming all_failed runs on success

2. Which of the following is the correct way to set a task's trigger rule to run if at least one upstream task succeeds in Airflow DAG code?

easy

A. trigger_rule='all_success'

B. trigger_rule='all_done'

C. trigger_rule='none_failed'

D. trigger_rule='one_success'

Solution

1. Step 1: Recall the trigger rule for running on any upstream success

   The trigger rule one_success runs the task if at least one upstream task succeeded.

2. Step 2: Check syntax correctness

   Setting trigger_rule='one_success' is the correct syntax in Airflow task definition.

3. Final Answer:

   trigger_rule='one_success' -> Option D

4. Quick Check:

   At least one success = trigger_rule='one_success' [OK]

Hint: Use trigger_rule='one_success' for any upstream success [OK]

Common Mistakes:

• Using all_success instead of one_success
• Misspelling trigger_rule or using wrong quotes
• Confusing none_failed with one_success

3. Given a DAG with three upstream tasks: task1 (success), task2 (skipped), task3 (failed). If a downstream task uses trigger_rule='none_failed', will it run?

medium

A. Yes, because no upstream task failed

B. No, because one upstream task failed

C. Yes, because at least one upstream succeeded

D. No, because all upstream tasks must succeed

Solution

1. Step 1: Understand none_failed trigger rule

   This rule runs the task only if no upstream task has failed. If any upstream failed, it will not run.

2. Step 2: Analyze upstream task states

   task3 failed, so the condition of no failures is false. Therefore, the downstream task will not run.

3. Final Answer:

   No, because one upstream task failed -> Option B

4. Quick Check:

   Any failure blocks none_failed run [OK]

Hint: If any upstream failed, none_failed won't run [OK]

Common Mistakes:

• Ignoring failed upstream tasks when using none_failed
• Confusing skipped with failed states
• Assuming none_failed runs if some succeed

4. You have a task with trigger_rule='one_success' but it never runs even though some upstream tasks succeed. What is the likely cause?

medium

A. The task has no upstream dependencies defined

B. The DAG is paused

C. The trigger_rule is misspelled or not set correctly

D. All upstream tasks failed

Solution

1. Step 1: Check trigger_rule spelling and assignment

   If the trigger_rule is misspelled or not properly set, Airflow defaults to all_success, causing the task not to run if not all upstream succeed.

2. Step 2: Verify other conditions

   Since some upstream succeed, and the task has dependencies, the most common cause is incorrect trigger_rule syntax.

3. Final Answer:

   The trigger_rule is misspelled or not set correctly -> Option C

4. Quick Check:

   Incorrect trigger_rule causes unexpected task skipping [OK]

Hint: Check trigger_rule spelling if task doesn't run as expected [OK]

Common Mistakes:

• Assuming upstream failure when some succeeded
• Ignoring DAG paused state
• Not defining upstream dependencies

5. You want a downstream task to run if either all upstream tasks succeed or if none failed but some were skipped. Which trigger rule should you use?

hard

A. none_failed

B. one_success

C. all_success

D. all_done

Solution

1. Step 1: Understand the requirement

   The task should run if all upstream succeeded or if none failed but some were skipped. This means failures block the run, but skips do not.

2. Step 2: Match with trigger rules

   all_success requires all succeed (no skips allowed). none_failed allows skips but no failures. one_success runs if any succeed, which is too loose. all_done runs regardless of success or failure.

3. Step 3: Choose the correct trigger rule

   none_failed fits the requirement exactly.

4. Final Answer:

   none_failed -> Option A

5. Quick Check:

   No failures but allows skips = none_failed [OK]

Hint: Use none_failed to allow skips but no failures [OK]

Common Mistakes:

• Choosing all_success which disallows skips
• Using one_success which is too permissive
• Confusing all_done with failure conditions