Generating airflow DAGs dynamically - airflow

Question

I am trying to generate airflow dags using a template in a python code, and using globals() as defined here
To define dag object and saving it. Below is my code :
import datetime as dt
import sys
import airflow
from airflow.models import DAG
from airflow.operators.bash_operator import BashOperator
argumentList = sys.argv
owner = argumentList[1]
dag_name = argumentList[2]
taskID = argumentList[3]
bashCommand = argumentList[4]
default_args = {
'owner': owner,
'start_date': dt.datetime(2019, 6, 1),
'retries': 1,
'retry_delay': dt.timedelta(minutes=5),
}
def dagCreate():
with DAG(dag_name,
default_args=default_args,
schedule_interval=None,
) as dag:
print_hello = BashOperator(task_id=taskID, bash_command=bashCommand)
return dag
globals()[dag_name] = dagCreate()
I have kept this python code outside dag_folder, and executing it as follows :
python bash-dag-generator.py Airflow test_bash_generate auto_bash_task ls
But I don't see any DAG generated in the airflow webserver UI. I am not sure where I am going wrong.

Answer 1

As per the official documentation:
DAGs are defined in standard Python files that are placed in Airflow’s DAG_FOLDER. Airflow will execute the code in each file to dynamically build the DAG objects. You can have as many DAGs as you want, each describing an arbitrary number of tasks. In general, each one should correspond to a single logical workflow.
So unless your code is actually inside the DAG_FOLDER, it will not be registered as a DAG.

Answer 2

The way I have been able to implement Dynamic DAGs is by using Airflow Variable.
In the below example I have a csv file that has list of Bash command like ls, echo etc. As part of the read_file task I am updating the file location to the Airflow Variable. The part where we read the csv file and loop through the commands is where the dynamic DAGs get created.
from airflow import DAG
from airflow.operators.python_operator import PythonOperator
from airflow.operators.bash_operator import BashOperator
from airflow.models import Variable
from datetime import datetime, timedelta
import csv
'''
Orchestrate the Dynamic Tasks
'''
def read_file_task():
print('I am reading a File and setting variables ')
Variable.set('dynamic-dag-sample','/home/bashoperator.csv')
with DAG('dynamic-dag-sample',
start_date=datetime(2018, 11, 1)) as dag:
read_file_task = PythonOperator(task_id='read_file_task',
python_callable=read_file_task, provide_context=True,
dag=dag)
dynamic_dag_sample_file_path = Variable.get("dynamic-dag-sample")
if dynamic_dag_sample_file_path != None:
with open(dynamic_dag_sample_file_path) as csv_file:
reader = csv.DictReader(csv_file)
line_count = 0
for row in reader:
bash_task = BashOperator(task_id=row['Taskname'], bash_command=row['Command'])
read_file_task.set_downstream(bash_task)