Debugging with Airflow CLI - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

Check DAG Run Status

You run the command airflow dags state example_dag 2023-06-01T00:00:00+00:00. What is the expected output if the DAG run succeeded?

A success

B failed

C running

D queued

💡 Hint

The command shows the state of a specific DAG run at the given execution date.

The airflow dags state command returns the state of the DAG run. If it succeeded, the output is exactly 'success'.

💻 Command Output

intermediate

Task Instance Log Retrieval

What output do you get when running airflow tasks logs example_dag example_task 2023-06-01T00:00:00+00:00 if the log file for that task instance does not exist?

A Task instance logs displayed successfully

B No logs found for task instance example_task on 2023-06-01T00:00:00+00:00

C FileNotFoundError: [Errno 2] No such file or directory

D Permission denied error

💡 Hint

Airflow CLI handles missing logs gracefully with a message.

If the log file is missing, Airflow CLI prints a friendly message indicating no logs found rather than a Python error.

🔀 Workflow

advanced

Order of Commands to Debug a Failed Task

Arrange the following Airflow CLI commands in the correct order to debug a failed task instance:

A 3,1,4,2

B 4,3,1,2

C 3,4,1,2

D 1,2,3,4

💡 Hint

Start by confirming the DAG exists, then list tasks, check task state, then view logs.

First list DAGs to confirm the DAG exists (3), then list tasks in the DAG (4), check the task state (1), and finally view logs for details (2).

❓ Troubleshoot

advanced

Identifying Cause of CLI Connection Error

You run airflow dags list but get the error: ConnectionRefusedError: [Errno 111] Connection refused. What is the most likely cause?

A Airflow webserver is not running

B Airflow scheduler is not running

C Airflow CLI is outdated

D Airflow metadata database is down

💡 Hint

The CLI connects to the metadata database to list DAGs.

The CLI needs to connect to the metadata database. If the database is down or unreachable, it raises ConnectionRefusedError.

✅ Best Practice

expert

Best Practice for Debugging Task Failures Using Airflow CLI

Which of the following is the best practice when using Airflow CLI to debug a task failure in production?

A Check the task instance state, then review logs before deciding to clear or rerun

B Directly clear the failed task instance using <code>airflow tasks clear</code> without checking logs

C Restart the entire Airflow scheduler to fix task failures

D Ignore CLI and only use the Airflow web UI for debugging

💡 Hint

Good debugging means understanding the failure before acting.

The best practice is to first check the task state and logs to understand the failure cause before clearing or rerunning tasks.

Practice

1. What is the primary purpose of the Airflow CLI command airflow tasks list DAG_ID?

easy

A. To show logs of a specific task

B. To run all tasks in a DAG immediately

C. To clear all task instances in a DAG

D. To display all tasks in a specific DAG

Solution

1. Step 1: Understand the command structure

   The command airflow tasks list DAG_ID is used to list tasks related to the DAG identified by DAG_ID.

2. Step 2: Identify the command's function

   This command shows all tasks defined in the DAG, helping users see what tasks exist.

3. Final Answer:

   To display all tasks in a specific DAG -> Option D

4. Quick Check:

   List tasks = Display tasks [OK]

Hint: List tasks to see all steps in a DAG quickly [OK]

Common Mistakes:

• Confusing 'list' with 'run' to execute tasks
• Thinking it clears tasks instead of listing
• Assuming it shows logs instead of task names

2. Which of the following is the correct Airflow CLI command to view logs for a task named task1 in DAG example_dag for execution date 2023-01-01T00:00:00?

easy

A. airflow tasks logs example_dag task1 2023-01-01T00:00:00

B. airflow logs example_dag task1 2023-01-01T00:00:00

C. airflow task logs example_dag task1 2023-01-01T00:00:00

D. airflow tasks log example_dag task1 2023-01-01T00:00:00

Solution

1. Step 1: Recall the correct Airflow CLI syntax for logs

   The correct command to view logs is airflow tasks logs DAG_ID TASK_ID EXECUTION_DATE.

2. Step 2: Match the command with the options

   airflow tasks logs example_dag task1 2023-01-01T00:00:00 matches the exact syntax with correct keywords and parameters.

3. Final Answer:

   airflow tasks logs example_dag task1 2023-01-01T00:00:00 -> Option A

4. Quick Check:

   Correct syntax for logs = airflow tasks logs example_dag task1 2023-01-01T00:00:00 [OK]

Hint: Use 'tasks logs' to view task logs with DAG and date [OK]

Common Mistakes:

• Using 'logs' without 'tasks' keyword
• Misspelling 'tasks' as 'task'
• Using 'log' instead of 'logs'

3. What will be the output of the command airflow tasks clear example_dag -t task1 -s 2023-01-01 -e 2023-01-02?

medium

A. It runs task1 in example_dag for the specified dates

B. It lists all tasks in example_dag between the given dates

C. It clears all task instances of task1 in example_dag between 2023-01-01 and 2023-01-02

D. It shows logs of task1 for the specified dates

Solution

1. Step 1: Understand the 'tasks clear' command

   The command airflow tasks clear removes task instance states, allowing rerun.

2. Step 2: Analyze the options -t, -s, -e

   -t specifies the task, -s and -e specify start and end dates for clearing task instances.

3. Final Answer:

   It clears all task instances of task1 in example_dag between 2023-01-01 and 2023-01-02 -> Option C

4. Quick Check:

   Clear task instances = It clears all task instances of task1 in example_dag between 2023-01-01 and 2023-01-02 [OK]

Hint: Clear tasks with -t for task and -s/-e for date range [OK]

Common Mistakes:

• Confusing clear with run or list commands
• Ignoring date range flags -s and -e
• Assuming it shows logs instead of clearing

4. You run airflow tasks run example_dag task1 2023-01-01 but get an error saying the task instance does not exist. What is the most likely cause?

medium

A. The command syntax is incorrect and missing required flags

B. The DAG is not loaded or paused, so the task instance is missing

C. The execution date format is wrong and not recognized

D. The task1 does not exist in any DAG

Solution

1. Step 1: Understand task instance creation

   Task instances exist only if the DAG is loaded and active (not paused).

2. Step 2: Identify why instance might be missing

   If the DAG is paused or not loaded, the task instance for the date won't exist, causing the error.

3. Final Answer:

   The DAG is not loaded or paused, so the task instance is missing -> Option B

4. Quick Check:

   Missing instance = DAG paused/not loaded [OK]

Hint: Check DAG status; paused DAGs block task instances [OK]

Common Mistakes:

• Assuming syntax error without checking DAG state
• Blaming date format without verifying
• Thinking task1 is missing from DAG

5. You want to debug a failed task task2 in DAG data_pipeline for execution date 2023-06-15T12:00:00. Which sequence of Airflow CLI commands helps you clear the failed task, rerun it, and then view its logs?

hard

A. airflow tasks clear data_pipeline -t task2 -s 2023-06-15T12:00:00 -e 2023-06-15T12:00:00 && airflow tasks run data_pipeline task2 2023-06-15T12:00:00 && airflow tasks logs data_pipeline task2 2023-06-15T12:00:00

B. airflow tasks run data_pipeline task2 2023-06-15T12:00:00 && airflow tasks clear data_pipeline -t task2 -s 2023-06-15T12:00:00 -e 2023-06-15T12:00:00 && airflow tasks logs data_pipeline task2 2023-06-15T12:00:00

C. airflow tasks logs data_pipeline task2 2023-06-15T12:00:00 && airflow tasks clear data_pipeline -t task2 -s 2023-06-15T12:00:00 -e 2023-06-15T12:00:00 && airflow tasks run data_pipeline task2 2023-06-15T12:00:00

D. airflow tasks clear data_pipeline -t task2 && airflow tasks logs data_pipeline task2 2023-06-15T12:00:00 && airflow tasks run data_pipeline task2 2023-06-15T12:00:00

Solution

1. Step 1: Clear the failed task instance for the exact execution date

   Use airflow tasks clear with task name and exact start/end date to reset the failed task.

2. Step 2: Run the cleared task instance

   Use airflow tasks run with DAG, task, and execution date to rerun the task.

3. Step 3: View the logs of the rerun task

   Use airflow tasks logs to check the output and debug information.

4. Final Answer:

   Clear, then run, then logs in sequence with correct dates -> Option A

5. Quick Check:

   Clear -> Run -> Logs = airflow tasks clear data_pipeline -t task2 -s 2023-06-15T12:00:00 -e 2023-06-15T12:00:00 && airflow tasks run data_pipeline task2 2023-06-15T12:00:00 && airflow tasks logs data_pipeline task2 2023-06-15T12:00:00 [OK]

Hint: Clear failed task first, then run, then check logs [OK]

Common Mistakes:

• Running task before clearing causes rerun failure
• Checking logs before rerun shows old failure logs
• Omitting date range in clear command