[GitHub] [airflow] stas-snow commented on issue #22193: max_active_runs = 1 can still create multiple active execution runs (again)

[GitBox <gi...@apache.org>]

stas-snow commented on issue #22193:
URL: https://github.com/apache/airflow/issues/22193#issuecomment-1067079346


   Code:
   
   ```
   import logging
   import time
   
   # Airflow packages
   from random import uniform
   from airflow.decorators import dag, task
   
   logger = logging.getLogger(__name__)
   
   default_dag_args = {
       'owner': 'airflow',
       'start_date': '2022-03-01',
       'schedule_interval': '@daily',
       'retries': 0,
       'catchup': True,
       'max_active_runs': 1,
       'depends_on_past': False,
   }
   
   
   @dag(default_args=default_dag_args)
   def test2_dag():
   
       @task()
       def start():
           logging.info("Starting DAG. Going to sleep")
           time.sleep(uniform(1, 5) * 60)
           logging.info("First task, exiting")
           return None
   
       @task()
       def do():
           time.sleep(uniform(1, 5) * 60)
           return None
   
       @task()
       def end():
           logging.info(f"Finishing...")
           time.sleep(3)
           return None
   
       # Define dependency between tasks
       start() >> do() >> end()
   
   
   # start the DAG
   test_pipeline = test2_dag()
   
   ```
   
   Screenshot of multiple DAG instances all in "Running" state.
   <img width="546" alt="image" src="https://user-images.githubusercontent.com/93541868/158224423-fae9b635-abd2-4be5-a292-fa2c6d3c5398.png">
   
   Documentation says that there should not be more than max_active_runs in Running state:
   ```
   max_active_runs – maximum number of active DAG runs, beyond this number of DAG runs in a running state, the scheduler won’t create new active DAG runs
   ```
   
   I would expect only 1 DAG in Running state if I have "max_active_runs = 1".
   


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