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Re: programmatically creating and airflow quirks



> On Nov 23, 2018, at 3:28 AM, Alex Guziel <alex.guziel@xxxxxxxxxx> wrote:
> 
> It’s because of this 
> 
> “When searching for DAGs, Airflow will only consider files where the string “airflow” and “DAG” both appear in the contents of the .py file.”
> 

Have not noticed it.  From airflow/models.py, in process_file — (both in 1.9 and 1.10)
..
if not all([s in content for s in (b'DAG', b'airflow')]):
..
is looking for those strings and if they are not found, it is returning without loading the DAGs.


So having “airflow” and “DAG”  dummy strings placed somewhere will make it work?


> On Thu, Nov 22, 2018 at 2:27 AM soma dhavala <soma.dhavala@xxxxxxxxx <mailto:soma.dhavala@xxxxxxxxx>> wrote:
> 
> 
>> On Nov 22, 2018, at 3:37 PM, Alex Guziel <alex.guziel@xxxxxxxxxx <mailto:alex.guziel@xxxxxxxxxx>> wrote:
>> 
>> I think this is what is going on. The dags are picked by local variables. I.E. if you do
>> dag = Dag(...)
>> dag = Dag(…)
> 
> from my_module import create_dag
> 
> for file in yaml_files:
> 	dag = create_dag(file)
> 	globals()[dag.dag_id] = dag
> 
> You notice that create_dag is in a different module. If it is in the same scope (file), it will be fine.
> 
>> 
> 
>> Only the second dag will be picked up.
>> 
>> On Thu, Nov 22, 2018 at 2:04 AM Soma S Dhavala <soma.dhavala@xxxxxxxxx <mailto:soma.dhavala@xxxxxxxxx>> wrote:
>> Hey AirFlow Devs:
>> In our organization, we build a Machine Learning WorkBench with AirFlow as
>> an orchestrator of the ML Work Flows, and have wrapped AirFlow python
>> operators to customize the behaviour. These work flows are specified in
>> YAML.
>> 
>> We drop a DAG loader (written python) in the default location airflow
>> expects the DAG files.  This DAG loader reads the specified YAML files and
>> converts them into airflow DAG objects. Essentially, we are
>> programmatically creating the DAG objects. In order to support muliple
>> parsers (yaml, json etc), we separated the DAG creation from loading. But
>> when a DAG is created (in a separate module) and made available to the DAG
>> loaders, airflow does not pick it up. As an example, consider that I
>> created a DAG picked it, and will simply unpickle the DAG and give it to
>> airflow.
>> 
>> However, in current avatar of airfow, the very creation of DAG has to
>> happen in the loader itself. As far I am concerned, airflow should not care
>> where and how the DAG object is created, so long as it is a valid DAG
>> object. The workaround for us is to mix parser and loader in the same file
>> and drop it in the airflow default dags folder. During dag_bag creation,
>> this file is loaded up with import_modules utility and shows up in the UI.
>> While this is a solution, but it is not clean.
>> 
>> What do DEVs think about a solution to this problem? Will saving the DAG to
>> the db and reading it from the db work? Or some core changes need to happen
>> in the dag_bag creation. Can dag_bag take a bunch of "created" DAGs.
>> 
>> thanks,
>> -soma
>