max_active_runs

[Gerard Toonstra]

A user on airflow 1.9.0 reports that 'max_active_runs' isn't respected. I
remembered having fixed something related to this ages ago and this is
here:

https://issues.apache.org/jira/browse/AIRFLOW-137

That however was related to backfills and clearing the dagruns.

I watched him in the scenario and he literally creates a new simple dag
with the following config:

-----

from airflow import DAG
from datetime import datetime, timedelta

from airflow.contrib.operators.bigquery_operator import BigQueryOperator
from airflow.contrib.operators.bigquery_to_gcs import
BigQueryToCloudStorageOperator
from airflow.contrib.operators.gcs_download_operator import
GoogleCloudStorageDownloadOperator
from airflow.contrib.operators.file_to_gcs import
FileToGoogleCloudStorageOperator
from airflow.operators.python_operator import PythonOperator
from airflow.models import Variable
import time

default_args = {
    'owner': 'airflow',
    'start_date': datetime(2018, 2, 10),
    'max_active_runs': 1,
    'email_on_failure': False,
    'email_on_retry': False,
}

dag = DAG('analytics6', default_args=default_args, schedule_interval='15 12
* * *')

-----

When it gets activated, multiple dagruns are created when there are still
tasks running on the first date.

His version is 1.9.0 from pypi.

Is max_active_runs broken or are there other explanations for this
particular behavior?

Rgds,

Gerard