Week 10: ETL Pipeline Orchestration with Airflow

DSAN 6000: Big Data and Cloud Computing
Fall 2025

Amit Arora and Jeff Jacobs

jj1088@georgetown.edu

Monday, November 3, 2025

Pipelines for Triggered Execution

…HEY! WAKE UP! NEW DATA JUST CAME IN!

You before this week:

  • Sprint to your .ipynb and/or Spark cluster
  • Load, clean, process new data, manually, step-by-step
  • Email update to boss

You after this week:

  • Asset-aware pipeline automatically triggered
  • Airflow orchestrates loading, cleaning, processing
  • EmailOperator sends update

Pipelines vs. Pipeline Orchestration

From Astronomer Academy’s Airflow 101

Key Airflow-Specific Buzzwords

(Underlined words link to Airflow docs “Core Concepts” section)

  • Directed Acyclic Graph (DAG): Your pipeline as a whole!

  • DAGs consist of multiple tasks, which you “string together” using the control flow operators >> and <<

  • [Ex ] second_task, third_task can’t start until first_task completes:

    first_task >> [second_task, third_task]
# Equivalent to:
first_task.set_downstream([second_task, third_task])

  • [Ex ] fourth_task can’t start until third_task completes:

    fourth_task << third_task
# Equivalent to:
fourth_task.set_upstream(third_task)

  • What kinds of tasks can we create? Brings us to another concept…

Operators: What Kind of task?

  • + Hundreds of “community provider” Operators:
  • HttpOperator
  • S3FileTransformOperator
  • SQLExecuteQueryOperator
  • EmailOperator
  • SlackAPIOperator

+ Jinja templating for managing how data “passes” from one step to the next:

Task vs. Operator: A Sanity-Preserving Distinction

From Operator docs:

When we talk about a Task, we mean the generic “unit of execution” of a DAG; when we talk about an Operator, we mean a [specific] pre-made Task template, whose logic is all done for you and that just needs some arguments.

Task:

Operator:

From Ruiter et al. (2026)

Concepts \(\leadsto\) Code

start-airflow.sh
airflow db migrate
airflow api-server --port 8080
airflow scheduler
airflow dag-processor
airflow triggerer
  • Full Airflow “ecosystem” is running once you’ve started each piece via above (bash) commands!
  • Let’s look at each in turn…

db migrate: The Airflow Metastore

start-airflow.sh
airflow db migrate
airflow api-server --port 8080
airflow scheduler
airflow dag-processor
airflow triggerer
  • General info used by DAGs: variables, connections, XComs
  • Data about DAG and task runs (generated by scheduler)
  • Logs / error information
  • Not modified directly/manually! Managed by Airflow; To modify, use API Server →

API Server

start-airflow.sh
airflow db migrate
airflow api-server --port 8080
airflow scheduler
airflow dag-processor
airflow triggerer

Web UI for managing Airflow (much more on this later!)

 Default Login Info

Default db migrate generates admin password in ~/simple_auth_manager_passwords.json.generated

Scheduler → Executor

start-airflow.sh
airflow db migrate
airflow api-server --port 8080
airflow scheduler
airflow dag-processor
airflow triggerer
  • Default: LocalExecutor
  • For scaling: EcsExecutor (AWS ECS), KubernetesExecutor
  • See also SparkSubmitOperator

From Ruiter et al. (2026)

DAG Processor

start-airflow.sh
airflow db migrate
airflow api-server --port 8080
airflow scheduler
airflow dag-processor
airflow triggerer

From Ruiter et al. (2026)

The schedule Argument

(Airflow uses pendulum under the hood, rather than datetime!)

dag_scheduling.py
from airflow.sdk import DAG
import pendulum
dag = DAG("regular_interval_cron_example", schedule="0 0 * * *", ...)
dag = DAG("regular_interval_cron_preset_example", schedule="@daily", ...)
dag = DAG("regular_interval_timedelta_example", schedule=pendulum.timedelta(days=1), ...)

Cron: Full-on scheduling language (used by computers since 1975!)

crontab.sh
# ┌───────────── minute (0–59)
# │ ┌───────────── hour (0–23)
# │ │ ┌───────────── day of the month (1–31)
# │ │ │ ┌───────────── month (1–12)
# │ │ │ │ ┌───────────── day of the week (0–6) (Sunday to Saturday)
# │ │ │ │ │
# │ │ │ │ │
# │ │ │ │ │
# * * * * * <command to execute>

Cron Presets: None, "@once", "@continuous", "@hourly", "@daily", "@weekly"

External Service Integration

Service Command
AWS pip install 'apache-airflow[amazon]'
Azure pip install 'apache-airflow[microsoft-azure]'
Databricks pip install 'apache-airflow[databricks]'
GitHub pip install 'apache-airflow[github]'
Google Cloud pip install 'apache-airflow[google]'
MongoDB pip install 'apache-airflow[mongo]'
OpenAI pip install 'apache-airflow[openai]'
Slack pip install 'apache-airflow[slack]'
Spark pip install 'apache-airflow[apache-spark]'
Tableau pip install 'apache-airflow[tableau]'

(And many more:)

Jinja Example

homepage.jinja
<h4>{{ me['name'] }}'s Favorite Hobbies</h4>
<ul>
{%- for hobby in hobbies %}
  <li>{{ hobby }}</li>
{%- endfor %}
</ul>
+ 
render_jinja.py
from jinja2 import Template
tmpl = Template('homepage.jinja')
tmpl.render(
    me = {'name': 'Jeff'},
    hobbies = [
        'eat',
        'sleep',
        'attend to the proverbial bag'
    ]
)
↓ 
rendered.html
<h4>Jeff's Favorite Hobbies</h4>
<ul>
  <li>eat</li>
  <li>sleep</li>
  <li>attend to the proverbial bag</li>
</ul>

\(\leadsto\)

Jeff's Favorite Hobbies

  • eat
  • sleep
  • attend to the proverbial bag

Airflow UI: Grid View

Airflow UI: Run Details

Airflow UI: Task Instance Details

Tasks → Task Groups

Graph View

Calendar View

Gantt View

New Book: Up-To-Date (Airflow 3.0) Demos 🤓

Harenslak and Ruiter (2021)

\(\leadsto\)

Ruiter et al. (2026)

Conceptual Pipelines \(\leadsto\) DAGs

Main challenge: converting “intuitive” pipelines in our heads:

From Ruiter et al. (2026)

Into DAGs with concrete Tasks, dependencies, and triggers:

Also from Ruiter et al. (2026)

Implementation Detail 1: Backfilling

Implementation Detail 2: Train Model Only After Backfill

\(\leadsto\)

LatestOnlyOperator

Fig 1: Both figures from Ruiter et al. (2026)

Implementation Detail 3: Downstream Consumers

From Ruiter et al. (2026)

Lab Time!

Lab 10: ETL Pipeline Orchestration with Airflow

References

Harenslak, Bas P., and Julian de Ruiter. 2021. Data Pipelines with Apache Airflow. Simon and Schuster.
Ruiter, Julian de, Ismael Cabral, Kris Geusebroek, Daniel van der Ende, and Bas Harenslak. 2026. Data Pipelines with Apache Airflow, Second Edition. Simon and Schuster.