| # |
| # Licensed to the Apache Software Foundation (ASF) under one |
| # or more contributor license agreements. See the NOTICE file |
| # distributed with this work for additional information |
| # regarding copyright ownership. The ASF licenses this file |
| # to you under the Apache License, Version 2.0 (the |
| # "License"); you may not use this file except in compliance |
| # with the License. You may obtain a copy of the License at |
| # |
| # http://www.apache.org/licenses/LICENSE-2.0 |
| # |
| # Unless required by applicable law or agreed to in writing, |
| # software distributed under the License is distributed on an |
| # "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY |
| # KIND, either express or implied. See the License for the |
| # specific language governing permissions and limitations |
| # under the License. |
| """Example DAG demonstrating the usage DAG params to model a trigger UI with a user form. |
| |
| This example DAG generates greetings to a list of provided names in selected languages in the logs. |
| """ |
| from __future__ import annotations |
| |
| import datetime |
| from pathlib import Path |
| |
| from airflow import DAG |
| from airflow.decorators import task |
| from airflow.models.dagrun import DagRun |
| from airflow.models.param import Param |
| from airflow.models.taskinstance import TaskInstance |
| from airflow.utils.trigger_rule import TriggerRule |
| |
| with DAG( |
| dag_id=Path(__file__).stem, |
| description=__doc__[0 : __doc__.find(".")], |
| doc_md=__doc__, |
| schedule=None, |
| start_date=datetime.datetime(2022, 3, 4), |
| catchup=False, |
| tags=["example_ui"], |
| params={ |
| "names": Param( |
| ["Linda", "Martha", "Thomas"], |
| type="array", |
| description="Define the list of names for which greetings should be generated in the logs." |
| " Please have one name per line.", |
| title="Names to greet", |
| ), |
| "english": Param(True, type="boolean", title="English"), |
| "german": Param(True, type="boolean", title="German (Formal)"), |
| "french": Param(True, type="boolean", title="French"), |
| }, |
| ) as dag: |
| |
| @task(task_id="get_names") |
| def get_names(**kwargs) -> list[str]: |
| ti: TaskInstance = kwargs["ti"] |
| dag_run: DagRun = ti.dag_run |
| if "names" not in dag_run.conf: |
| print("Uuups, no names given, was no UI used to trigger?") |
| return [] |
| return dag_run.conf["names"] |
| |
| @task.branch(task_id="select_languages") |
| def select_languages(**kwargs) -> list[str]: |
| ti: TaskInstance = kwargs["ti"] |
| dag_run: DagRun = ti.dag_run |
| selected_languages = [] |
| for lang in ["english", "german", "french"]: |
| if lang in dag_run.conf and dag_run.conf[lang]: |
| selected_languages.append(f"generate_{lang}_greeting") |
| return selected_languages |
| |
| @task(task_id="generate_english_greeting") |
| def generate_english_greeting(name: str) -> str: |
| return f"Hello {name}!" |
| |
| @task(task_id="generate_german_greeting") |
| def generate_german_greeting(name: str) -> str: |
| return f"Sehr geehrter Herr/Frau {name}." |
| |
| @task(task_id="generate_french_greeting") |
| def generate_french_greeting(name: str) -> str: |
| return f"Bonjour {name}!" |
| |
| @task(task_id="print_greetings", trigger_rule=TriggerRule.ALL_DONE) |
| def print_greetings(greetings1, greetings2, greetings3) -> None: |
| for g in greetings1 if greetings1 else []: |
| print(g) |
| for g in greetings2 if greetings2 else []: |
| print(g) |
| for g in greetings3 if greetings3 else []: |
| print(g) |
| if not greetings1 and not greetings2 and not greetings3: |
| print("sad, nobody to greet :-(") |
| |
| lang_select = select_languages() |
| names = get_names() |
| english_greetings = generate_english_greeting.expand(name=names) |
| german_greetings = generate_german_greeting.expand(name=names) |
| french_greetings = generate_french_greeting.expand(name=names) |
| lang_select >> [english_greetings, german_greetings, french_greetings] |
| results_print = print_greetings(english_greetings, german_greetings, french_greetings) |