Apache airflow macro to get last dag run execution time

Question

I thought the macro prev_execution_date listed here would get me the execution date of the last DAG run, but looking at the source code it seems to only get the

Answer 1

Yes, you can define your own custom macro for this as follows:

# custom macro function
def get_last_dag_run(dag):
    last_dag_run = dag.get_last_dagrun()
    if last_dag_run is None:
        return "no prev run"
    else:
        return last_dag_run.execution_date.strftime("%Y-%m-%d")

# add macro in user_defined_macros in dag definition
dag = DAG(dag_id="my_test_dag",
      schedule_interval='@daily',
      user_defined_macros={
          'last_dag_run_execution_date': get_last_dag_run
      }
)

# example of using it in practice
print_vals = BashOperator(
    task_id='print_vals',
    bash_command='echo {{ last_dag_run_execution_date(dag) }}',
    dag=dag
)

Note that the dag.get_last_run() is just one of the many functions available on the Dag object. Here's where I found it: https://github.com/apache/incubator-airflow/blob/v1-10-stable/airflow/models.py#L3396

You can also tweak the formatting of the string for the date format, and what you want output if there is no previous run.