How to Mute Failure for a Specific Airflow Task?

Question

I set up a conditional task in airflow described here . All it does is to check if a hive partition exists. If yes, proceed with the rest of the tasks, and if not, add partition first before proceeding. The conditional check task can either fail or succeed, both are okay. However, I have the pager duty email notification set up for the dag because I want to know when the downstream tasks fail. How do I mute failure notification on that specific conditional task so that I don't get a false alarm on pager duty?

Answer 1

email_on_failure and on_failure_callback etc. are task (operator) level parameters. They inherit from DAG object, value of default_args you passed to the DAG, but also you can overwrite them on initialization.

YourOperator(task_id='task1', dag=dag, email_on_failure=None, on_failure_callback=None, ...)

here is the source code how airflow handle those callbacks when task fails, make you more clear how it works.

def handle_failure(self, error, test_mode=False, context=None):
        self.log.exception(error)
        task = self.task
        session = settings.Session()
        self.end_date = datetime.utcnow()
        self.set_duration()
        Stats.incr('operator_failures_{}'.format(task.__class__.__name__), 1, 1)
        Stats.incr('ti_failures')
        if not test_mode:
            session.add(Log(State.FAILED, self))

        # Log failure duration
        session.add(TaskFail(task, self.execution_date, self.start_date, self.end_date))

        # Let's go deeper
        try:
            # Since this function is called only when the TI state is running,
            # try_number contains the current try_number (not the next). We
            # only mark task instance as FAILED if the next task instance
            # try_number exceeds the max_tries.
            if task.retries and self.try_number <= self.max_tries:
                self.state = State.UP_FOR_RETRY
                self.log.info('Marking task as UP_FOR_RETRY')
                if task.email_on_retry and task.email:
                    self.email_alert(error, is_retry=True)
            else:
                self.state = State.FAILED
                if task.retries:
                    self.log.info('All retries failed; marking task as FAILED')
                else:
                    self.log.info('Marking task as FAILED.')
                if task.email_on_failure and task.email:
                    self.email_alert(error, is_retry=False)
        except Exception as e2:
            self.log.error('Failed to send email to: %s', task.email)
            self.log.exception(e2)

        # Handling callbacks pessimistically
        try:
            if self.state == State.UP_FOR_RETRY and task.on_retry_callback:
                task.on_retry_callback(context)
            if self.state == State.FAILED and task.on_failure_callback:
                task.on_failure_callback(context)
        except Exception as e3:
            self.log.error("Failed at executing callback")
            self.log.exception(e3)

        if not test_mode:
            session.merge(self)
        session.commit()
        self.log.error(str(error))

https://airflow.apache.org/_modules/airflow/models.html#BaseOperator