What is Apache Airflow - CLI Guide

Introduction

Apache Airflow helps you organize and run tasks automatically in a specific order. It solves the problem of managing many steps that depend on each other, like a recipe for a cake but for computer jobs.

When you want to run data processing steps one after another without doing it manually.

When you need to schedule tasks to run at certain times, like every day or every hour.

When you want to see if your tasks worked or failed and get alerts.

When you have many tasks that depend on each other and want to manage their order easily.

When you want to reuse and share task workflows with your team.

Commands

This command sets up the database Airflow uses to keep track of tasks and workflows.

Terminal

airflow db init

Expected Output

INFO  [alembic.runtime.migration] Context impl PostgresqlImpl.

INFO  [alembic.runtime.migration] Will assume transactional DDL.

INFO  [alembic.runtime.migration] Running upgrade head

INFO  [alembic.runtime.migration] Upgrade successful

Creates an admin user so you can log into the Airflow web interface and manage workflows.

Terminal

airflow users create --username admin --firstname Admin --lastname User --role Admin --email [e-mail] --password admin123

Expected Output

User created successfully

→

--username - Set the login name

→

--role - Set user permissions

→

--password - Set the login password

Starts the Airflow web interface on port 8080 so you can see and control your workflows in a browser.

Terminal

airflow webserver --port 8080

Expected Output

[2024-06-01 12:00:00,000] {webserver.py:123} INFO - Starting web server on port 8080

→

--port - Choose the port number for the web interface

Starts the scheduler that runs your tasks at the right time and in the right order.

Terminal

airflow scheduler

Expected Output

[2024-06-01 12:00:05,000] {scheduler.py:456} INFO - Starting the scheduler

Key Concept

If you remember nothing else, remember: Apache Airflow lets you automate and monitor complex task workflows easily.

Common Mistakes

Not initializing the database before starting Airflow

Airflow needs the database to store task info; without it, Airflow won't work.

Always run 'airflow db init' before starting the webserver or scheduler.

Forgetting to create a user before accessing the web interface

Without a user, you cannot log in to manage workflows.

Create at least one user with 'airflow users create' before starting the webserver.

Running the webserver and scheduler in the same terminal without backgrounding

One process will block the other, so both won't run properly.

Run them in separate terminals or use background processes.

Summary

Initialize Airflow's database with 'airflow db init' to prepare the system.

Create a user to access the Airflow web interface using 'airflow users create'.

Start the webserver to view and control workflows in a browser.

Run the scheduler to execute tasks automatically in the right order.