Status

Motivation

Airflow Examples have been grown in number and focus over the past years. They purpose multiple things:

• Serve as tutorials to learn Airflow DAG implementation
• Serve with code snippets for documentation
• Serve for testing the setup
• (some) service for CI integration testing

Some example DAGs are in a good quality, some are not following best practices. Current examples do not follow a structure.

There are example DAGs contained in the Airflow core (currently pushed to standard provider/example_dags) as well as there are more examples in other providers. But examples from other providers are lot loaded automatically.

So in the Airflow 3 Dev Calls there was a demand named to clean-up and optimize example DAGs.

Considerations / Targets

• The number of examples should be reduced to 20-30
  • If possible examples from docs should be represented in examples. Some code examples which are stand-alone in code should be moved into examples if possible.
  • Otherwise example content not referenced in documentation might be questioned if beneficial
• Examples should be arranged along a story-line if possible which might represent a virtual company and support real-life use cases. Might be good if we can structure it as growth of use-cases bringing in need for more features. i.e. starting off basic transformation → needing more complex task so using groups → using sensors, assets... showing progression of usage with project/company maturity. 
  
• Examples should follow best practices in coding
• Existing examples should be reviewed which DAGs are just used for testing. Testing DAGs should be separated and not pollute the example collection
• Some examples are specific for providers. They should be moved to provider packages
• A mechanism is to be created that uses DAG bundle loading mechanism to load example DAGs from providers w/o need to copy them to global examples.
• Same like today if loading of example DAGs is enabled also needed plugins e.g. timetables should be usable out-of-the-box
• (more tbd?)

Storyline

Current ideas collection:

• "Tailwind" - A virtual / non existing wind park energy company that powers a farm of win-mills to produce clean energy. The company has a strong demand to ETL sensor data from the windmills as well as need to act on data events when base data changes or contracts with customers renew. The company values also the DEI rules and has sustainable targets for clean energy and CO2 reduction.
  • Event driven case: New data is dropped on a file system (S3 would be great but can not be executed w/o S3, can be added to AWS provider as extension) that triggers data processing for wind energy. Data is loaded  and Asset events are generated
  • Asset driven pipeline around reporting,  data is split up per city of wind turbine and reports about production are distributed to shareholders. Branching can be used to check if a notification is sent via email or a custom notifier. This can also use branch labels. A third notification channel might be broken and as these shareholders are important we inform the admin in case of any task fails (trigger rule) and start a recovery task.
  • Scheduled nightly use case, example reporting is written to file system (where event pipeline is picking up!). As it would be too easy some tasks migth fail and then a custom weight rule is used for retries.
  • Manual correction trigger: Correction wind production counters can be submitted which then also are written to file system
  • Timetable example for maintenance schedule (selected calendar dates) where maintenance notifications are sent
  • Scheduled hourly check for wind turbines state. This requires som special infrastructure to start and stop, using setup+teardown to open a VPN tunnel to the remote machines. This is using a generator pattern and produces the same logic for 3 counties.

As for demos and examples a lot of functionality is needed in both decorator as well as classic Dag implementation it would be good to have two similar use cases. Or alternatively dscribe that the Tailwind south branch prefers to implement all in Pythonic manner whereas the Tailwind North branch data engineers like the classic implementation?

rankdir=LR;
  node [style=rounded]
  node1 [shape=box]
  node2 [fillcolor=lightblue, style="rounded,filled", shape=diamond]
  node3 [shape=record, label="{ a | b | c }"]
  node1 -> node2 -> node3

Technical Work Packages → Features

• --load-example-dags must load examples from standard provider at least in Airflow 3.1 (same like in breeze hack today)
• Testing DAGs must be loadable (at least in breeze) to be able to remove them from example tree
  Likely we should have a dedicated "test_dags" folder/bundle that should contain dags used for testing only. We can automatically add such dags to be used in unit test via auto-fixture in the shared conftest.py or similar - this way it will work in both breeze and local venv. I think we should aim to have breeze == local env
  
• DAG Bundles must be extended depending on installed/available providers to extend examples - allowing to move examples from core to providers (e.g. example_kubernetes_executor.py → cncf.kubernetes)
  Likely we can add "examples" section in provider.yaml and move the example dags from "tests" to separate "examples" folder that will be also embedded in the .whl file (so that you can also conditionally enable examples from a given provider). This means that "system" tests will not be a separate "system" folder, but something separate.
  

• We should figure out a way how to show examples from a provider - possibly "load_core_examples=true/false" and "load_provider_examples=[list of providers]" would be a nice way how to do it

• The example have to be reviewed with  "security" point of view. We often have security reports that are pointing to RCE , lack of sanitizations etc. in our examples - which is very important as those examples can be used by others and bad practices propagated to production code.

• Add a review checklist into the repo to remember the qulity gates we defined for future reviews and extensions after the examples have been cleaned-up.

Proposed Technical Excellence in Example DAGs

• All code has documentation (pydoc)
• All DAGs have DAG MD docs and task MD docs
  The MD must include a lightweight Dag Preview - Let's Include a short summary (1–2 sentences) in the Dag’s description, explaining what it demonstrates/features and why it’s useful. So that users don't have to really go through the story to understand that one feature.
  The MD should include links to the official Airflow documentation. This would provide users with instant access to deeper reference material for operators, hooks, or features being demonstrated, without them needing to search separately.
• All DAGs and Tasks use Typing
• The Examples use tags mapping to use cases of storyline.
  • All examples carry the the tag "Example"
  • If the DAG is serving as a tutorial, it is having the tag "Tutorial"
  • Current examples that we move off for testing (or which are dual-use) get a tag "Testing"

  • Feature Tags for Easier Discoverability - The new storyline-based example Dags are great for understanding end-to-end workflows. That said, they can be a bit overwhelming if you’re just looking to learn a specific concept (e.g., Dynamic Task Mapping, Assets, Sensors, XCom). It helps to add feature tags to each Dag. So users can more easily find Dags showcasing a specific capability. We should maintain a specific set of tags.

• Ruff + Mypy checks are enabled and examples follow code quality guidelines
• DAGs and Tasks have nice display names
• Examples do not use deprecated functions
• Examples do not carry top-level code
• Code in the examples follow best practices with regards to security (sanitizatio, RCE protection, no exposure of sensitive information and the like)
• All examples are running in the standard setup out-of-the-box. They need to run out-of-the-box (e.g. no connections, SW packages need to be created prior run)
  Note: This will not be possible for some provider examples - for example Google  - they need at least configuration of Google connection and some of them need a separate setup. Possibly in those cases we should just document prerequisites for them. Or we need to find other creative options like checking for existence and short-circuit if per-requisites are not existing (e.g. a snowflake back-end needed). If can be set-up automatically then setup- and teardown tasks might be an option.
• Examples should integrate into the story-line and not just stand-alone to showcase a technical feature
• All xamples should be (if possible) available as Taskflow and Non-Taskflow (we call it Classic in the examples)

Current Examples → Example DAG Target Panning

See https://github.com/apache/airflow/tree/main/airflow-core/src/airflow/example_dags

Name	Gaps	Referenced in	Features used	Proposed Change
Core - airflow-core/src/airflow/example_dags
example_asset_alias.py		-	AssetAlias, taskflow	Documentation in https://airflow.apache.org/docs/apache-airflow/stable/authoring-and-scheduling/assets.html#dynamic-data-events-emitting-and-asset-creation-through-assetalias does not use the examples. Either ned to add to real-world example, refernce it in docs or delete them. Unknown User (uranusjr) Do you have an ida how to map this to a real world example
example_asset_alias_with_no_taskflow.py		-	AssetAlias
example_asset_decorator.py		-	assets, decorators	Basic examples should be integrated into the storyline. Else too many dags w/o business example. Then drop
example_assets.py		-	assets
example_asset_with_watchers.py		-	AssetWatcher	Needs to be intgrated into case, not standalone. Then drop
example_branch_labels.py		airflow-core/docs/core-concepts/dags.rst		Needs to be intgrated into case, not standalone. Then drop
example_branch_python_dop_operator_3.py		-		Needs to be intgrated into case, not standalone, then drop
example_complex.py		airflow-core/docs/howto/usage-cli.rst		Lags a real business case. But complexity might be still a good show case. Check for the resulting example, if similar complexity then drop
example_custom_weight.py		airflow-core/docs/administration-and-deployment/priority-weight.rst	priority weights,	Just a technical example. Needs to be kept but would be best to integrate in a real use case.
example_dag_decorator.py		airflow-core/docs/core-concepts/dags.rst		Not needed as standalone example if the business example contains similar code. Rework into a real business example then Drop
example_display_name.py		-		Drop standalone example. Ral display names should be added to all examples. → Drop
example_dynamic_task_mapping.py		airflow-core/docs/authoring-and-scheduling/dynamic-task-mapping.rst	Dynamic task mapping	Nice example. But use one alternative from real life and drop the individual dag then
example_dynamic_task_mapping_with_no_taskflow_operators.py		airflow-core/docs/authoring-and-scheduling/dynamic-task-mapping.rst	Dynamic task mapping
example_inlet_event_extra.py		-		Needs a proper example to showcase something useful. Unknown User (uranusjr) do you have a real world example to add to the storyline  Then rework on this together with outlet events. Then drop this example as standaone file.
example_kubernetes_executor.py		providers/cncf/kubernetes/docs/kubernetes_executor.rst		Move to K8s Provider
example_latest_only_with_trigger.py		airflow-core/docs/core-concepts/dags.rst		I (= Unknown User (jscheffl)) do not understand the example as well as not the benefit of this Operator. Is there anybody who can provide a real life example of use? Else drop
example_local_kubernetes_executor.py		-		Move to K8s Provider
example_nested_branch_dag.py		-		Not of any use standalone. Drop
example_outlet_event_extra.py		-		Same like example_inlet_event_extra.py
example_params_trigger_ui.py		airflow-core/docs/core-concepts/params.rst		Migrate to storyline, then drop the individual example
example_params_ui_tutorial.py		airflow-core/docs/core-concepts/params.rst		If not all features can be transferred into storyline, keep this as individual example to be able to test all form elements.
example_passing_params_via_test_command.py		-		Migrate to storyline, then drop the individual example
example_setup_teardown.py		-		Migrate to storyline, then drop the individual example
example_setup_teardown_taskflow.py		-
example_simplest_dag.py		-		Merge with tutorial. No value standalone
example_skip_dag.py		-		Should be integrated into storyline and be added as code reference in docs. Then Drop this example
example_task_group_decorator.py		airflow-core/docs/core-concepts/dags.rst	Task Group	Migrate to storyline, then drop the individual example
example_task_group.py		-	Task Group
example_time_delta_sensor_async.py		-		Merge with tutorial. No value standalone
example_trigger_target_dag.py		-		Ups, this DAG was forgotten to be moved to standard provider → But anyway: Migrate to storyline, then drop the individual example
example_workday_timetable.py		code copied, not inlined in airflow-core/docs/howto/timetable.rst		Use as a base for one of the examples in the storyline, then Drop
example_xcomargs.py		-		Use as a base for one of the examples in the storyline, then Drop
example_xcom.py		-		Use as a base for one of the examples in the storyline, then Drop
tutorial_dag.py		-		Consolidate with tutorial.py Note is referenced in some tests and needs to be replaces with the other tutorial
tutorial_objectstorage.py		airflow-core/docs/tutorial/objectstorage.rst
tutorial.py		airflow-core/docs/core-concepts/dag-run.rst airflow-core/docs/tutorial/fundamentals.rst		Keep as starter tutorial, beautify using technical rules
tutorial_taskflow_api.py		airflow-core/docs/tutorial/taskflow.rst
tutorial_taskflow_api_virtualenv.py		-		Check if features can be added to storyline for technical completeness, then drop
tutorial_taskflow_templates.py		-		Check if features can be added to storyline for technical completeness, then drop
Standard - providers/standard/tests/system/standard
example_bash_decorator.py		providers/standard/docs/operators/bash.rst		Keep
example_bash_operator.py		providers/standard/docs/operators/bash.rst airflow-core/docs/core-concepts/debug.rst contributing-docs/quick-start-ide/contributors_quick_start_vscode.rst		Keep
example_branch_datetime_operator.py		providers/standard/docs/operators/datetime.rst		Keep, but need a better idea
example_branch_day_of_week_operator.py		providers/standard/docs/operators/datetime.rst
example_branch_operator_decorator.py		providers/standard/docs/operators/python.rst
example_branch_operator.py		providers/standard/docs/operators/python.rst
example_external_task_child_deferrable.py		-
example_external_task_marker_dag.py		providers/standard/docs/sensors/external_task_sensor.rst
example_external_task_parent_deferrable.py		providers/standard/docs/sensors/external_task_sensor.rst
example_latest_only.py		providers/standard/docs/operators/latest_only.rst
example_python_decorator.py		airflow-core/docs/tutorial/taskflow.rst providers/standard/docs/operators/python.rst
example_python_operator.py		airflow-core/docs/best-practices.rst providers/standard/docs/operators/python.rst
example_sensor_decorator.py		airflow-core/docs/tutorial/taskflow.rst providers/standard/docs/sensors/python.rst
example_sensors.py		providers/standard/docs/sensors/bash.rst providers/standard/docs/sensors/datetime.rst providers/standard/docs/sensors/file.rst providers/standard/docs/sensors/python.rst
example_short_circuit_decorator.py		providers/standard/docs/operators/python.rst
example_short_circuit_operator.py		providers/standard/docs/operators/python.rst
example_trigger_controller_dag.py		providers/standard/docs/operators/trigger_dag_run.rst		See example_trigger_target_dag.py
ArangoDB - providers/arangodb/src/airflow/providers/arangodb/example_dags
example_arangodb.py		providers/arangodb/docs/operators/index.rst
Oracle - providers/oracle/src/airflow/providers/oracle/example_dags
example_oracle.py		providers/oracle/docs/operators.rst
Edge - providers/edge3/src/airflow/providers/edge3/example_dags
integration_test.py		-
win_notepad.py		-
win_test.py		-

List of features to cover in new examples