Airflow architecture (scheduler, webserver, executor, metadata DB) - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Role of the Airflow Scheduler

What is the primary role of the Airflow scheduler in the system?

A It triggers tasks based on their schedules and manages task dependencies.

B It provides the user interface to monitor workflows.

C It stores all task logs and metadata.

D It executes tasks on worker nodes.

💡 Hint

Think about which component decides when tasks should run.

The scheduler is responsible for triggering tasks according to their schedules and managing dependencies between tasks.

💻 Command Output

intermediate

Output of Airflow Webserver Command

What output will you see when you run airflow webserver successfully?

Apache Airflow

airflow webserver

A Executing scheduled tasks

B Starting the web server on port 8080

C Connecting to metadata database failed

D Worker nodes started

💡 Hint

The webserver is responsible for the UI, so it should start a server.

Running airflow webserver starts the web interface, usually on port 8080.

❓ Configuration

advanced

Configuring the Executor in Airflow

Which configuration snippet correctly sets the Airflow executor to CeleryExecutor in airflow.cfg?

A

[webserver]
executor = CeleryExecutor

B

[scheduler]
executor = CeleryExecutor

C

[core]
executor = CeleryExecutor

D

[database]
executor = CeleryExecutor

💡 Hint

Executor setting is under the core section.

The executor is configured under the [core] section in airflow.cfg.

❓ Troubleshoot

advanced

Metadata Database Connection Issue

If Airflow components cannot connect to the metadata database, which symptom is most likely observed?

A Scheduler fails to schedule tasks and logs connection errors.

B Webserver UI loads normally but tasks do not run.

C Executor runs tasks without any errors.

D Worker nodes start and execute tasks successfully.

💡 Hint

Metadata DB is critical for scheduler operation.

The scheduler relies on the metadata database to track task states; connection failure causes scheduling errors.

🔀 Workflow

expert

Order of Airflow Component Startup

What is the correct order to start Airflow components for a CeleryExecutor setup?

A 3,1,2,4

B 2,1,4,3

C 1,3,2,4

D 1,2,3,4

💡 Hint

Database must be ready before scheduler and workers start.

The metadata database must start first, then the scheduler, followed by the webserver and workers.