Pass other arguments to on_failure_callback

Question

I'd like to pass other arguments to my on_failure_callback function but it only seems to want "context". How do I pass other arguments to that function...especially since I'd like to define that function in a separate module so it can be used in all my DAGS.

My current default_args looks like this:

default_args = {
  'owner': 'Me',
  'depends_on_past': True,
  'start_date': datetime(2016,01,01),
  'email': ['[email protected]'],
  'email_on_failure': False,
  'email_on_retry': False,
  'retries': 1,
  'retry_delay': timedelta(minutes=1),
  'on_failure_callback': notify_failure,
  'max_active_runs': 1
}

If I try something like this airflow complains:

default_args = {
  'owner': 'Me',
  'depends_on_past': True,
  'start_date': datetime(2016,01,01),
  'email': ['[email protected]'],
  'email_on_failure': False,
  'email_on_retry': False,
  'retries': 1,
  'retry_delay': timedelta(minutes=1),
  'on_failure_callback': notify_failure(context,arg1,arg2),
  'max_active_runs': 1
}

so not sure how to pass arg1 and arg2 to my notify_failure fuction that I would like to define in a separate module that I can simply import into my DAG

Answer 1

Assuming the args are something you can define at the DAG level, then you can use the partials package. ie:

from functools import partial

def generic_failure(arg1, arg2, context):
  # do whatever

default_args = {
  'owner': 'Me',
  'depends_on_past': True,
  'start_date': datetime(2016,01,01),
  'email': ['[email protected]'],
  'email_on_failure': False,
  'email_on_retry': False,
  'retries': 1,
  'retry_delay': timedelta(minutes=1),
  'on_failure_callback': partial(generic_failure, arg1, arg2),
  'max_active_runs': 1
}

Calling partial(generic_failure, arg1, arg2) will return a function expecting however many arguments are remaining in generic_failure, which in the above example is just the single param context

Answer 2

you can use a nested function for this

def generic_failure(arg1, arg2):
    def failure(context):
        message = 'we have a function that failed witg args : {ARG1}, {ARG2}'.format(ARG1=arg1,ARG2=arg2)
        print(message)
        return message
    return failure

arg1 = 'arg1'
arg2 = 'arg2'

default_args = {
  'owner': 'Me',
  'on_failure_callback': generic_failure(arg1, arg2),
}