airflow/models/dagbag.py
def get_dag(self, dag_id):
        """
        Gets the DAG out of the dictionary, and refreshes it if expired
        """
        from airflow.models.dag import DagModel  # Avoid circular import

        # If asking for a known subdag, we want to refresh the parent
        root_dag_id = dag_id
        if dag_id in self.dags:
            dag = self.dags[dag_id]
            if dag.is_subdag:
                root_dag_id = dag.parent_dag.dag_id

        # If the dag corresponding to root_dag_id is absent or expired
        orm_dag = DagModel.get_current(root_dag_id)
        if orm_dag and (
                root_dag_id not in self.dags or
                (
                    orm_dag.last_expired and
                    dag.last_loaded < orm_dag.last_expired
                )
        ):
            # Reprocess source file
            found_dags = self.process_file(
                filepath=orm_dag.fileloc, only_if_updated=False)

            # If the source file no longer exports `dag_id`, delete it from self.dags
            if found_dags and dag_id in [found_dag.dag_id for found_dag in found_dags]:
                return self.dags[dag_id]
            elif dag_id in self.dags:
                del self.dags[dag_id]
        return self.dags.get(dag_id)
def get_dag(self, dag_id):
        """
        Gets the DAG out of the dictionary, and refreshes it if expired
        """
        from airflow.models.dag import DagModel  # Avoid circular import

        # If asking for a known subdag, we want to refresh the parent
        root_dag_id = dag_id
        if dag_id in self.dags:
            dag = self.dags[dag_id]
            if dag.is_subdag:
                root_dag_id = dag.parent_dag.dag_id

        # If the dag corresponding to root_dag_id is absent or expired
        orm_dag = DagModel.get_current(root_dag_id)
        if orm_dag and (
                root_dag_id not in self.dags or
                (
                    orm_dag.last_expired and
                    dag.last_loaded < orm_dag.last_expired
                )
        ):
            # Reprocess source file
            found_dags = self.process_file(
                filepath=orm_dag.fileloc, only_if_updated=False)

            # If the source file no longer exports `dag_id`, delete it from self.dags
            if found_dags and dag_id in [found_dag.dag_id for found_dag in found_dags]:
                return self.dags[dag_id]
            elif dag_id in self.dags:
                del self.dags[dag_id]
        return self.dags.get(dag_id)
Gets the DAG out of the dictionary, and refreshes it if expired